Editing IPCC:AR6/WGIII/TS (section)

== TS.5 Mitigation Responses in Sectors and Systems ==

<div id="h1-5-siblings" class="h1-siblings"></div>

Chapters 5 to 12 assess recent advances in knowledge in individual sectors and systems. These chapters – ''Energy'' (Chapter 6), ''Urban and Other Settlements'' (Chapter 8) '', Transport'' (Chapter 10) '', Buildings'' Chapter 9) '', Industry'' (Chapter 11), and ''Agriculture, Forestry and Other Land Use (AFOLU)'' (Chapter 7) ''–'' correspond broadly to the IPCC National Greenhouse Gas Inventory reporting categories and build on similar chapters in previous WGIII reports. Chapters 5 and 12 tie together the cross-sectoral aspects of this group of chapters including the assessment of costs and potentials, demand-side aspects of mitigation, and carbon dioxide removal (CDR).

<div id="TS.5.1" class="h2-container"></div>

<span id="ts.5.1-energy"></span>
=== TS.5.1 Energy ===

<div id="h2-3-siblings" class="h2-siblings"></div>

'''A broad-based approach to deploying energy-sector mitigation options can reduce emissions over the next ten years and set the stage for still deeper reductions beyond 2030 (''' '''''high confidence''''' ''').''' There are substantial, cost-effective opportunities to reduce emissions rapidly, including in electricity generation, but near-term reductions will not be sufficient to limit warming to 2°C (&gt;67%) or limit warming to 1.5°C (&gt;50%) with no or limited overshoot. {6.4, 6.6, 6.7}

'''Warming cannot be limited to 2°C or 1.5°C without rapid and deep reductions in energy system CO''' 2 '''and GHG emissions (''' '''''high confidence''''' ''').''' In scenarios limiting warming to 1.5°C (&gt;50%) with no or limited overshoot ( ''likely'' below 2°C), net energy system CO 2 emissions fall by 87–97% (interquartile range 60–79%) in 2050. In 2030, in scenarios limiting warming to 1.5°C with no or limited overshoot, net CO 2 and GHG emissions fall by 35–51% and 38–52% respectively. In scenarios limiting warming to 1.5°C with no or limited overshoot ( ''likely'' below 2°C), net electricity sector CO 2 emissions reach zero globally between 2045 and 2055 (2050 and 2080) ( ''high confidence'' ) ''.'' {6.7}

'''Limiting warming to 2°C or 1.5°C will require substantial energy system changes over the next 30 years. This includes reduced fossil fuel consumption, increased production from low- and zero-carbon energy sources, and increased use of electricity and alternative energy carriers (''' '''''high confidence''''' ''').''' Coal consumption without CCS falls by 67–82% (interquartile range) in 2030 in scenarios limiting warming to 1.5°C with no or limited overshoot. Oil and gas consumption fall more slowly. Low-carbon sources produce 93–97% of global electricity by 2050 in scenarios that limit warming to 2°C (&gt;67%) or below. In scenarios limiting warming to 1.5°C with no or limited overshoot ( ''likely'' below 2°C), electricity supplies 48–58% (36–47%) of final energy in 2050, up from 20% in 2019. {6.7}

'''Net zero energy systems will share common characteristics, but the approach in every country will depend on national circumstances (''' '''''high confidence''''' ''').''' Common characteristics of net-zero energy systems will include: (i) electricity systems that produce no net CO ''2'' or remove CO ''2'' from the atmosphere; (ii) widespread electrification of end uses, including light-duty transport, space heating, and cooking; (iii) substantially lower use of fossil fuels than today; (iv) use of alternative energy carriers such as hydrogen, bioenergy, and ammonia to substitute for fossil fuels in sectors less amenable to electrification; (v) more efficient use of energy than today; (vi) greater energy system integration across regions and across components of the energy system; and (vii) use of CO ''2'' removal including DACCS and BECCS to offset residual emissions. {6.6}

'''Energy demands and energy sector emissions have continued to rise (''' '''''high confidence''''' ''').''' From 2015 to 2019, global final energy consumption grew by 6.6%, CO 2 emissions from the global energy system grew by 4.6%, and total GHG emissions from energy supply rose by 2.7%. Fugitive CH 4 emissions from oil, gas, and coal, accounted for 18% of GHG emissions in 2019. Coal electricity capacity grew by 7.6% between 2015 and 2019, as new builds in some countries offset declines in others. Total consumption of oil and oil products increased by 5%, and natural gas consumption grew by 15%. Declining energy intensity in almost all regions has been balanced by increased energy consumption. {6.3}

'''The unit costs for several key energy system mitigation options have dropped rapidly over the last five years, notably solar PV, wind power, and batteries (''' '''''high confidence''''' ''').''' From 2015 to 2020, the costs of electricity from PV and wind dropped 56% and 45%, respectively, and battery prices dropped by 64%. Electricity from PV and wind is now cheaper than electricity from fossil sources in many regions, electric vehicles are increasingly competitive with internal combustion engines, and large-scale battery storage on electricity grids is increasingly viable. (Figure TS.7) {6.3, 6.4}

'''Global wind and solar PV capacity and generation have increased rapidly driven by policy, societal pressure to limit fossil generation, low interest rates, and cost reductions (''' '''''high confidence''''' ''').''' Solar PV grew by 170% (to 680 TWh); wind grew by 70% (to 1420 TWh) from 2015 to 2019. Solar PV and wind together accounted for 21% of total low-carbon electricity generation and 8% of total electricity generation in 2019. Nuclear generation grew 9% between 2015 and 2019 and accounted for 10% of total generation in 2019 (2790 TWh); hydro-electric power grew by 10% and accounted for 16% (4290 TWh) of total generation. In total, low- and zero-carbon electricity generation technologies produced 37% of global electricity in 2019. {6.3, 6.4}

'''If investments in coal and other fossil infrastructure continue, energy systems will be locked-in to higher emissions, making it harder to limit warming to 2°C or 1.5°C (''' '''''high confidence''''' ''').''' Many aspects of the energy system – physical infrastructure; institutions, laws, and regulations; and behaviour – are resistant to change or take many years to change. New investments in coal-fired electricity without CCS are inconsistent with limiting warming to well below 2°C. {6.3, 6.7}

'''Limiting warming to 2°C or 1.5°C will strand fossil-related assets, including fossil infrastructure and unburned fossil fuel resources (''' '''''high confidence''''' ''').''' The economic impacts of stranded assets could amount to trillions of dollars. Coal assets are most vulnerable over the coming decade; oil and gas assets are more vulnerable toward mid-century. CCS can allow fossil fuels to be used longer, reducing potential stranded assets. (Box TS.8) {6.7}

'''Box TS.8 | Stranded Assets'''

Limiting warming to 2°C or 1.5°C is expected to result in the ‘stranding’ of carbon-intensive assets. Stranded assets can be broadly defined as assets which ‘suffer from unanticipated or premature write-offs, downward revaluations or conversion to liabilities’. Climate policies, other policies and regulations, innovation in competing technologies, and shifts in fuel prices could all lead to stranded assets. The loss of wealth from stranded assets would create risks for financial market stabilityand reduce fiscal revenue for hydrocarbon-dependent economies, which in turn could affect macroeconomic stability and the prospects for a Just Transition. (Box TS.4) {6.7, 15.6, Chapter 17}

Two types of assets are at risk of being stranded: (i) in-ground fossil resources and (ii) human-made capital assets (e.g., power plants and cars). About 30% of oil, 50% of gas, and 80% of coal reserves will remain unburnable if warming is limited to 2°C. {6.7, Box 6.11}

Practically all long-lived technologies and investments that cannot be adapted to low-carbon and zero-emission modes could face stranding under climate policy – depending on their current age and expected lifetimes. Scenario evidence suggests that without carbon capture, the worldwide fleet of coal- and gas power plants would need to retire about 23 and 17 years earlier than expected lifetimes, respectively, in order to limit global warming to 1.5°C and 2°C {2.7} . Blast furnaces and cement factories without CCS {11.4} , new fleets of airplanes and internal combustion engine vehicles {10.4, 10.5} , and new urban infrastructures adapted to sprawl and motorisation may also be stranded. {Chapter 8; Box 10.1}

Many countries, businesses, and individuals stand to lose wealth from stranded assets. Countries, businesses, and individuals may therefore desire to keep assets in operation even if financial, social, or environmental concerns call for retirement. This creates political economic risks, including actions by asset owners to hinder climate policy reform {6.7; Box 6.11} . It will be easier to retire these assets if the risks are communicated, if sustainability reporting is mandated and enforced, and if corporations are protected with arrangements that shield them from short-term shareholder value maximisation.

Without early retirements, or reductions in utilisation, the current fossil infrastructure will emit more GHGs than is compatible with limiting warming to 1.5°C {2.7} . Including the pipeline of planned investments would push these future emissions into the uncertainty range of 2°C carbon budgets {2.7} . Continuing to build new coal-fired power plants and other fossil infrastructure will increase future transition costs and may jeopardise efforts to limit warming to 2°C (&gt;67%) or 1.5°C with no or limited overshoot. One study has estimated that USD11.8 trillion in current assets will need to be stranded by 2050 for a 2°C world; further delaying action for another 10 years would result in an additional USD7.7 trillion in stranded assets by 2050. {15.5.2}

Experience from past stranding indicates that compensation for the devaluation costs of private-sector stakeholders by the public sector is common. Limiting new investments in fossil technologies hence also reduces public finance risks in the long term. {15.6.3}

'''A low-carbon energy transition will shift investment patterns and create new economic opportunities (''' '''''high confidence''''' ''').''' Total energy investment needs will rise, relative to today, over the next decades, if warming is limited to 2°C or lower (&gt;67%), or if warming is limited to 1.5°C (&gt;50%) with no or limited overshoot. These increases will be far less pronounced, however, than the reallocations of investment flows that are anticipated across subsectors, namely from fossil fuels (extraction, conversion, and electricity generation) without CCS and toward renewables, nuclear power, CCS, electricity networks and storage, and end-use energy efficiency. A significant and growing share of investments between now and 2050 will be made in emerging economies, particularly in Asia. {6.7}

'''Climate change will affect many future local and national low-carbon energy systems. The impacts, however, are uncertain, particularly at the regional scale (''' '''''high confidence''''' ''').''' Climate change will alter hydropower production, bioenergy and agricultural yields, thermal power plant efficiencies, and demands for heating and cooling, and it will directly impact power system infrastructure. Climate change will not affect wind and solar resources to the extent that it would compromise their ability to reduce emissions. {6.5}

'''Electricity systems powered predominantly by renewables will be increasingly viable over the coming decades, but it will be challenging to supply the entire energy system with renewable energy (''' '''''high confidence''''' ''').''' Large shares of variable solar PV and wind power can be incorporated in electricity grids through batteries, hydrogen, and other forms of storage; transmission; flexible non-renewable generation; advanced controls; and greater demand-side responses. Because some applications (e.g., aviation) are not currently amenable to electrification, it is anticipated that 100% renewable energy systems will need to include alternative fuels such as hydrogen or biofuels. Economic, regulatory, social, and operational challenges increase with higher shares of renewable electricity and energy. The ability to overcome these challenges in practice is not fully understood. (Box TS.9) {6.6}

'''Box TS.9 | The Transformation in Energy Carriers: Electrification and Hydrogen'''

To use energy, it must be ‘carried’ from where it was produced – at a power plant, for example, or a refinery, or a coal mine – to where it is used. As countries reduce CO 2 emissions, they will need to switch from gasoline and other petroleum-based fuels, natural gas, coal, and electricity produced from these fossil fuels to energy carriers with little or no carbon footprint. An important question is which new energy carriers will emerge to support low-carbon transitions.

Low-carbon energy systems are expected to rely heavily on end-use electrification, where electricity produced with low GHG emissions is used for building and industrial heating, transport and other applications that rely heavily on fossil fuels at present. But not all end-uses are expected to be commercially electrifiable in the short to medium term {11.3.5} , and many will require low GHG liquid and gaseous fuels, that is, hydrogen, ammonia, and biogenic and synthetic low GHG hydrocarbons made from low GHG hydrogen, oxygen and carbon sources (the latter from CCU, [[#footnote-013|20]] biomass, or direct air capture {11.3.6} ). The future role of hydrogen and hydrogen derivatives will depend on how quickly and how far production technology improves, that is, from electrolysis (‘green’), biogasification, and fossil fuel reforming with CCS (‘blue’) sources. As a general rule, and across all sectors, it is more efficient to use electricity directly and avoid the progressively larger conversion losses from producing hydrogen, ammonia, or constructed low GHG hydrocarbons. What hydrogen does do, however, is add time and space option value to electricity produced using variable clean sources, for use as hydrogen, as stored future electricity via a fuel cell or turbine, or as an industrial feedstock. Furthermore, electrification and hydrogen involve a symbiotic range of general-purpose technologies, such as electric motors, power electronics, heat pumps, batteries, electrolysis, fuel cells, and so on, that have different applications across sectors but cumulative economies of innovation and production scale benefits. Finally, neither electrification nor hydrogen produce local air pollutants at point of end-use.

For almost 140 years we have primarily produced electricity by burning coal, oil, and gas to drive steam turbines connected to electricity generators. When switching to low-carbon energy sources – renewable sources, nuclear power, and fossil or bioenergy with CCS – electricity is expected to become a more pervasive energy carrier. Electricity is a versatile energy carrier, with much higher end-use efficiencies than fuels, and it can be used directly to avoid conversion losses.

An increasing reliance on electricity from variable renewable sources, notably wind and solar power, disrupts old concepts and makes many existing guidelines obsolete for power system planning, for example, that specific generation types are needed for baseload, intermediate load, and peak load to follow and meet demand. In future power systems with high shares of variable electricity from renewable sources, system planning and markets will focus more on demand flexibility, grid infrastructure and interconnections, storage on various timelines (on the minute, hourly, overnight and seasonal scale), and increased coupling between the energy sector and the building, transport and industrial sectors. This shifts the focus to energy systems that can handle variable supply rather than always follow demand. Hydrogen may prove valuable to improve the resilience of electricity systems with high penetration of variable renewable electricity. Flexible hydrogen electrolysis, hydrogen power plants and long-duration hydrogen storage may all improve resilience. Electricity-to-hydrogen-to-electricity round-trip efficiencies are projected to reach up to 50% by 2030. {6.4.3}

Electrification is expected to be the dominant strategy in buildings as electricity is increasingly used for heating and for cooking. Electricity will help to integrate renewable energy into buildings and will also lead to more flexible demand for heating, cooling, and electricity. District heating and cooling offers potential for demand flexibility through energy storage and supply flexibility through cogeneration. Heat pumps are increasingly used in buildings and industry for heating and cooling {9.3.3, Box 9.3} . The ease of switching to electricity means that hydrogen is not expected to be a dominant pathway for buildings {Box 9.6} . Using electricity directly for heating, cooling and other building energy demand is more efficient than using hydrogen as a fuel, for example, in boilers or fuel cells. In addition, electricity distribution is already well developed in many regions compared to essentially non-existent hydrogen infrastructure, except for a few chemicals industry pipelines. At the same time, hydrogen could potentially be used for on-site storage should technology advance sufficiently.

Electrification is already occurring in several modes of personal and light-freight transport, and vehicle-to-grid solutions for flexibility have been extensively explored in the literature and small-scale pilots. The role of hydrogen in transport depends on how far technology develops. Batteries are currently a more attractive option than hydrogen and fuel cells for light-duty vehicles. Hydrogen and hydrogen-derived synthetic fuels, such as ammonia and methanol, may have a more important role in heavy vehicles, shipping, and aviation {10.3} . Current transport of fossil fuels may be replaced by future transport of hydrogen and hydrogen carriers such as ammonia and methanol, or energy-intensive basic materials processed with hydrogen (e.g., reduced iron) in regions with bountiful renewable resources. {Box 11.1}

Both light and heavy industry are potentially large and flexible users of electricity for both final energy use (e.g., directly and using heat pumps in light industry) and for feedstocks (e.g., hydrogen for steel-making and chemicals). For example, industrial process heat demand, ranging from below 100°C to above 1000°C, can be met through a wide range of electrically powered technologies instead of using fuels. Future demand for hydrogen (e.g., for nitrogen fertiliser or as a reduction agent in steel production) also offers electricity-demand flexibility for electrolysis through hydrogen storage and flexible production cycles {11.3.5} . The main use of hydrogen and hydrogen carriers in industry is expected to be as feedstock (e.g., for ammonia and organic chemicals) rather than for energy as industrial electrification increases.

'''Multiple energy supply options are available to reduce emissions over the next decade (''' '''''high confidence''''' ''').''' Nuclear power and hydropower are already established technologies. Solar PV and wind are now cheaper than fossil-generated electricity in many locations. Bioenergy accounts for about a tenth of global primary energy. Carbon capture is widely used in the oil and gas industry, with early applications in electricity production and biofuels. It will not be possible to widely deploy all of these and other options without efforts to address the geophysical, environmental-ecological, economic, technological, socio-cultural, and institutional factors that can facilitate or hinder their implementation ( ''high confidence'' ). (Figures TS.11 and TS.31) {6.4}

<div id="_idContainer041" class="Basic-Text-Frame"></div>

[[File:4e1c634a3164090c964d9d102e81fb3a IPCC_AR6_WGIII_Figure_TS_11_1.png]]

[[File:42cb1dec2f67a4bea8f0dfc8888a2811 IPCC_AR6_WGIII_Figure_TS_11_2.png]]

[[File:a62dbec05279c8725f284bc755d227a6 IPCC_AR6_WGIII_Figure_TS_11_3.png]]

'''Figure TS.11''' '''continued: Global energy flows within the 2019 global energy system (top panel) and within two illustrative future, net-zero CO''' 2 '''emissions global energy system (bottom panels).''' Source: IEA, AR6 Scenarios Database. Flows below 1 EJ are not represented. The illustrative net-zero scenarios correspond to the years in which net energy system CO 2 emissions reach zero – 2045 in IMP-Ren and 2060 in IMP-Neg-2.0. Source: data from IMP-Ren: Luderer et al.(2022); IMP-Neg-2.0: Riahi, K. et al. 2021.

'''Enhanced integration across energy system sectors and across scales will lower costs and facilitate low-carbon energy system transitions (''' '''''high confidence''''' ''').''' Greater integration between the electricity sector and end-use sectors can facilitate integration of variable renewable energy options. Energy systems can be integrated across district, regional, national, and international scales ( ''high confidence'' ) ''.'' {6.4, 6.6}

'''The viable speed and scope of a low-carbon energy system transition will depend on how well it can support SDGs and other societal objectives (''' '''''high confidence''''' ''').''' Energy systems are linked to a range of societal objectives, including energy access, air and water pollution, health, energy security, water security, food security, economic prosperity, international competitiveness, and employment. These linkages and their importance vary among regions. Energy-sector mitigation and efforts to achieve SDGs generally support one another, though there are important region-specific exceptions ( ''high confidence'' ) ''.'' (Figure TS.29) {6.1, 6.7}

'''The economic outcomes of low-carbon transitions in some sectors and regions may be on par with, or superior to those of an emissions-intensive future (''' '''''high confidence''''' ''').''' Cost reductions in key technologies, particularly in electricity and light-duty transport, have increased the economic attractiveness of near-term low-carbon transitions. Long-term mitigation costs are not well understood and depend on policy design and implementation, and the future costs and availability of technologies. Advances in low-carbon energy resources and carriers such as next-generation biofuels, hydrogen produced from electrolysis, synthetic fuels, and carbon-neutral ammonia would substantially improve the economics of net zero energy systems ( ''medium confidence'' ). {6.4, 6.7}

<div id="TS.5.2" class="h2-container"></div>

<span id="ts.5.2-urban-systems-and-other-settlements"></span>

=== TS.5.2 Urban Systems and Other Settlements ===

<div id="h2-4-siblings" class="h2-siblings"></div>

'''Although urbanisation is a global trend often associated with increased incomes and higher consumption, the growing concentration of people and activities is an opportunity to increase resource efficiency and decarbonise at scale (''' '''''very high confidence''''' ''').''' The same urbanisation level can have large variations in per-capita urban carbon emissions. For most regions, per-capita urban emissions are lower than per-capita national emissions (excluding aviation, shipping and biogenic sources) ( ''very high confidence'' ). {8.1.4, 8.3.3, 8.4, Box 8.1}

'''Most future urban population growth will occur in developing countries, where per-capita emissions are currently low, but are expected to increase with the construction and use of new infrastructure, and the built environment, and changes in incomes and lifestyles (''' '''''very high confidence''''' ''').''' The drivers of urban GHG emissions are complex and include an interplay of population size, income, state of urbanisation, and how cities are laid out (i.e., urban form). How new cities and towns are designed, constructed, managed, and powered will lock-in behaviour, lifestyles, and future urban GHG emissions. Urban strategies can improve well-being while minimising impact on GHG emissions. However, urbanisation can result in increased global GHG emissions through emissions outside the city’s boundaries ( ''very high confidence'' ) ''.'' {8.1.4, 8.3, Box 8.1, 8.4, 8.6}

'''The urban share of combined global CO''' 2 '''and CH''' ''4'' ''') emissions is substantial and continues to increase (''' '''''high confidence''''' ''').''' In 2015, urban emissions were estimated to be 25GtCO 2 -eq (about 62% of the global share) and in 2020 were 29 GtCO 2 -eq (67–72% of the global share). [[#footnote-012|21]] Around 100 of the highest-emitting urban areas account for approximately 18% of the global carbon footprint ( ''high confidence'' ) ''.'' {8.1, 8.3}

'''The urban share of regional GHG emissions increased between 2000 and 2015, with much inter-regional variation in the magnitude of the increase (''' '''''high confidence''''' ''').''' Globally, the urban share of national emissions increased six percentage points, from 56% in 2000 to 62% in 2015. For 2000 to 2015, the urban emissions share increased from 28% to 38% in Africa, from 46% to 54% in Asia and Pacific, from 62% to 72% in Developed Countries, from 57% to 62% in Eastern Europe and West Central Asia, from 55% to 66% in Latin America and Caribbean, and from 68% to 69% in the Middle East ( ''high confidence'' ) ''.'' {8.1.6, 8.3.3}

'''Per-capita urban GHG emissions increased between 2000 and 2015, with cities in developed countries accounting for nearly seven times more per capita than the lowest emitting region (''' '''''medium confidence''''' ''').''' From 2000 to 2015, global urban GHG emissions per capita increased from 5.5 to 6.2 tCO ''2'' -eq per person (an increase of 11.8%). Emissions in Africa increased from 1.3 to 1.5 tCO ''2'' -eq per person (22.6%); in Asia and Pacific from 3.0 to 5.1 tCO ''2'' -eq per person (71.7%); in Eastern Europe and West Central Asia from 6.9 to 9.8 tCO ''2'' -eq per person (40.9%); in Latin America and the Caribbean from 2.7 to 3.7 tCO ''2'' -eq per person (40.4%); and in the Middle East from 7.4 to 9.6 tCO ''2'' -eq per person (30.1%). Albeit starting from the highest level, developed countries showed a modest decline of 11.4 to 10.7 tCO ''2'' -eq per person (–6.5%). (Figure TS.12) {8.3.3}

<div id="_idContainer028xa" class="Basic-Text-Frame"></div>

[[File:4380759f11e9130fda70104d4d1d5afb IPCC_AR6_WGIII_Figure_TS_12.png]]

'''Figure TS.12''' '''|''' '''Changes in six metrics associated with urban and national-scale combined CO''' 2 '''and CH''' 4 '''emissions represented in the AR6 WGIII six-region aggregation, with (a) 2000 and (b) 2015.''' The trends in Luqman et al. (2021) were combined with the work of Moran et al. (2018) to estimate the regional urban CO 2 -eq share of global urban emissions, the urban share of national CO 2 -eq emissions, and the urban per capita CO 2 -eq emissions by region. This estimate is derived from consumption-based accounting that includes both direct emissions from within urban areas and indirect emissions from outside urban areas related to the production of electricity, goods, and services consumed in cities. It incorporates all CO 2 and CH 4 emissions except aviation, shipping and biogenic sources (i.e., land-use change, forestry, and agriculture). The dashed grey line represents the global average urban per capita CO 2 -eq emissions. The regional urban population share, regional CO 2 -eq share in total emissions, and national per capita CO 2 -eq emissions by region are given for comparison. Source: adapted from Gurney et al. (2022).

'''The global share of future urban GHG emissions is expected to increase through 2050 with moderate to low mitigation efforts due to growth trends in population, urban land expansion, and infrastructure and service demands, but the extent of the increase depends on the scenario and the scale and timing of urban mitigation action (''' '''''medium confidence''''' ''').''' [[#footnote-011|22]] In modelled scenarios, global consumption-based urban CO 2 and CH 4 emissions are projected to rise from 29 GtCO 2 -eq in 2020 to 34 GtCO 2 -eq in 2050 with moderate mitigation efforts (intermediate GHG emissions, SSP2-4.5), and up to 40 GtCO 2 -eq in 2050 with low mitigation efforts (high GHG emissions, SSP 3-7.0). With aggressive and immediate mitigation efforts to limit global warming to 1.5°C (&gt;50%) with no or limited overshoot by the end of the century (very low emissions, SSP1-1.9), including high levels of electrification, energy and material efficiency, renewable energy preferences, and socio-behavioural responses, urban GHG emissions could approach net-zero and reach a maximum of 3 GtCO 2 -eq in 2050. Under a scenario with aggressive but not immediate urban mitigation policies to limit global warming to 2°C (&gt;67%) (low emissions, SSP1-2.6), urban emissions could reach 17 GtCO 2 -eq in 2050. [[#footnote-010|23]] (Figure TS.13) {8.3.4}

<div id="_idContainer045" class="Basic-Text-Frame"></div>

[[File:7a24c7b2cddd21441d72a66b28d6fd07 IPCC_AR6_WGIII_Figure_TS_13.png]]

'''Figure''' '''TS.13 | Panel (a): carbon dioxide-equivalent emissions from global urban areas from 1990 to 2100. Urban areas are aggregated to six regional domains;''' '''Panel (b): comparison of urban emissions under different urbanisation scenarios (GtCO''' 2 '''-eq yr''' –1 ''') for different regions.''' 21 {Figures 8.13 and 8.14}

'''Urban land areas could triple between 2015 and 2050, with significant implications for future carbon lock-in (''' '''''medium confidence''''' ''').''' There is a large range in the forecasts of urban land expansion across scenarios and models, which highlights an opportunity to shape future urban development towards low- or net zero GHG emissions. By 2050, urban areas could increase up to 211% over the 2015 global urban extent, with the median projected increase ranging from 43% to 106%. While the largest absolute amount of new urban land is forecasted to occur in Asia and Pacific, and in Developed Countries, the highest rate of urban land growth is projected to occur in Africa, Eastern Europe and West Central Asia, and in the Middle East. Given past trends, the expansion of urban areas is expected to take place on agricultural lands and forests, with implications for the loss of carbon stocks. The infrastructure that will be constructed concomitant with urban land expansion will lock-in patterns of energy consumption that will persist for decades. {8.3.1, 8.3.4, 8.4.1, 8.6}

'''The construction of new, and upgrading of existing, urban infrastructure through 2030 will add to emissions (''' '''''medium evidence, high agreement''''' ''').''' The construction of new and upgrading of existing urban infrastructure using conventional practices and technologies can result in a significant increase in CO 2 emissions, ranging from 8.5 GtCO 2 to 14 GtCO 2 annually up to 2030 and more than double annual resource requirements for raw materials to about 90 billion tonnes per year by 2050, up from 40 billion tonnes in 2010. {8.4.1, 8.6}

'''Given the dual challenges of rising urban GHG emissions and future projections of more frequent extreme climate events, there is an urgent need to integrate urban mitigation and adaptation strategies for cities to address climate change (''' '''''very high confidence''''' ''').''' Mitigation strategies can enhance resilience against climate change impacts while contributing to social equity, public health, and human well-being. Urban mitigation actions that facilitate economic decoupling can have positive impacts on employment and local economic competitiveness. {8.2, Cross-Working Group Box 2 in Chapter 8, 8.4}

'''Cities can achieve net-zero GHG emissions only through deep decarbonisation and systemic transformation (''' '''''very high confidence''''' ''').''' Three broad mitigation strategies have been found to be effective in reducing emissions when implemented concurrently: (i) reducing or changing urban energy and material use towards more sustainable production and consumption across all sectors, including through compact and efficient urban forms and supporting infrastructure; (ii) electrification and switching to low-carbon energy sources; and (iii) enhancing carbon uptake and storage in the urban environment ( ''high confidence'' ). Given the regional and global reach of urban supply chains, cities can achieve net-zero emissions only if emissions are reduced both within and outside of their administrative boundaries through supply chains. {8.1.6, 8.3.4, 8.4, 8.6}

'''Packages of mitigation policies that implement multiple urban-scale interventions can have cascading effects across sectors, reduce GHG emissions outside a city’s administrative boundaries, and reduce emissions more than the net sum of individual interventions, particularly if multiple scales of governance are included (''' '''''high confidence''''' ''').''' Cities have the ability to implement policy packages across sectors using an urban systems approach, especially those that affect key infrastructure based on spatial planning, electrification of the urban energy system, and urban green and blue infrastructure. The institutional capacity of cities to develop, coordinate, and integrate sectoral mitigation strategies within their jurisdiction varies by context, particularly those related to governance, the regulatory system, and budgetary control. {8.4, 8.5, 8.6}

'''Integrated spatial planning to achieve compact and resource-efficient urban growth through co-location of higher residential and job densities, mixed land use, and transit-oriented development could reduce urban energy use between 23% and 26% by 2050 compared to the business-as-usual scenario (''' '''''high confidence''''' ''').''' Compact cities with shortened distances between housing and jobs, and interventions that support a modal shift away from private motor vehicles towards walking, cycling, and low-emissions shared, or public, transportation, passive energy comfort in buildings, and urban green infrastructure can deliver significant public health benefits and lower GHG emissions. {8.2, 8.3.4, 8.4, 8.6}

'''Urban green and blue infrastructure can mitigate climate change through carbon sinks, avoided emissions, and reduced energy use while offering multiple co-benefits (''' '''''high confidence''''' ''').''' Urban green and blue infrastructure, including urban forests and street trees, permeable surfaces, and green roofs [[#footnote-009|24]] offer potentials to mitigate climate change directly through storing carbon, and indirectly by inducing a cooling effect that both reduces energy demand and reduces energy use for water treatment. Globally, urban trees store approximately 7.4 billion tonnes of carbon, and sequester approximately 217 million tonnes of carbon annually, although carbon storage is highly dependent on biome. Among the multiple co-benefits of green and blue infrastructure are reducing the urban heat island (UHI) effect and heat stress, reducing stormwater runoff, improving air quality, and improving the mental and physical health of urban dwellers. Many of these options also provide benefits to climate adaptation. ( ''high agreement, robust evidence'' ) {8.2, 8.4.4}

'''The potential and sequencing of mitigation strategies to reduce GHG emissions will vary depending on a city’s land use, spatial form, development level, and state of urbanisation (i.e., whether it is an established city with existing infrastructure, a rapidly growing city with new infrastructure, or an emerging city with infrastructure buildup) (''' '''''high confidence''''' ''').''' New and emerging cities will have significant infrastructure development needs to achieve high quality of life, which can be met through energy-efficient infrastructures and services, and people-centred urban design (high confidence). The long lifespan of urban infrastructures locks in behaviour and committed emissions. Urban infrastructures and urban form can enable sociocultural and lifestyle changes that can significantly reduce carbon footprints. Rapidly growing cities can avoid higher future emissions through urban planning to co-locate jobs and housing to achieve compact urban form, and by leapfrogging to low-carbon technologies. Established cities will achieve the largest GHG emissions savings by replacing, repurposing, or retrofitting the building stock, targeted infilling and densifying, as well as through modal shift and the electrification of the urban energy system. New and emerging cities have unparalleled potential to become low or net zero GHG emissions while achieving high quality of life by creating compact, co-located, and walkable urban areas with mixed land use and transit-oriented design, that also preserve existing green and blue assets. {8.2, 8.4, 8.6}

'''With over 880 million people living in informal settlements, there are opportunities to harness and enable informal practices and institutions in cities related to housing, waste, energy, water, and sanitation to reduce resource use and mitigate climate change (''' '''''low evidence, medium agreement''''' ''').''' The upgrading of informal settlements and inadequate housing to improve resilience and well-being offers a chance to create a low-carbon transition. However, there is limited quantifiable data on these practices and their cumulative impacts on GHG emissions. {8.1.4, 8.2.2, Cross-Working Group Box 2 in Chapter 8, 8.3.2, 8.4, 8.6, 8.7}

'''Achieving transformational changes in cities for climate change mitigation and adaptation will require engaging multiple scales of governance, including governments and non-state actors, and in connection with substantial financing beyond sectoral approaches (''' '''''very high confidence''''' ''').''' Large and complex infrastructure projects for urban mitigation are often beyond the capacity of local municipality budgets, jurisdictions, and institutions. Partnerships between cities and international institutions, national and regional governments, transnational networks, and local stakeholders play a pivotal role in mobilising global climate finance resources for a range of infrastructure projects with low-carbon emissions and related spatial planning programs across key sectors. {8.4, 8.5}

<div id="TS.5.3" class="h2-container"></div>

<span id="ts.5.3-transport"></span>

=== TS.5.3 Transport ===

<div id="h2-5-siblings" class="h2-siblings"></div>

'''Meeting climate mitigation goals would require transformative changes in the transport sector.''' In 2019, direct GHG emissions from the transport sector were 8.7 GtCO 2 -eq (up from 5.0 GtCO ''2'' -eq in 1990) and accounted for 23% of global energy-related CO 2 emissions. Road vehicles accounted for 70% of direct transport emissions, while 1%, 11%, and 12% of direct emissions came from rail, shipping, and aviation, respectively. Emissions from shipping and aviation continue to grow rapidly. Transport-related emissions in developing regions of the world have increased more rapidly than in Europe or North America, a trend that is expected to continue in coming decades ( ''high confidence'' ). {10.1, 10.5, 10.6}

'''Since AR5 there has been a growing awareness of the need for demand management solutions combined with new technologies, such as the rapidly growing use of electromobility for land transport and the emerging options in advanced biofuels and hydrogen-based fuels for shipping and aviation and in other specific land-based contexts (''' '''''high confidence''''' ''').''' There is a growing need for systemic infrastructure changes that enable behavioural modifications and reductions in demand for transport services that can in turn reduce energy demand. The response to the COVID-19 pandemic has also shown that behavioural interventions can reduce transport-related GHG emissions. For example, COVID-19-based lockdowns have confirmed the transformative value of telecommuting replacing significant numbers of work and personal journeys as well as promoting local active transport. There are growing opportunities to implement strategies that drive behavioural change and support the adoption of new transport technology options. {Chapter 5, 10.2, 10.3, 10.4, 10.8}

'''Changes in urban form, behaviour programs, the circular economy, the shared economy, and digitalisation trends can support systemic changes that lead to reductions in demand for transport services or expand the use of more efficient transport modes (''' '''''high confidence''''' ''').''' Cities can reduce their transport-related fuel consumption by around 25% through combinations of more compact land use and the provision of less car-dependent transport infrastructure. Appropriate infrastructure, including protected pedestrian and bike pathways, can also support much greater localised active travel. [[#footnote-008|25]] Transport demand management incentives are expected to be necessary to support these systemic changes. There is mixed evidence of the effect of circular economy initiatives, shared economy initiatives, and digitalisation on demand for transport services (Box TS.14). For example, while dematerialisation can reduce the amount of material that needs to be transported to manufacturing facilities, an increase in online shopping with priority delivery can increase demand for freight transport. Similarly, while teleworking could reduce travel demand, increased ride-sharing could increase vehicle kilometres travelled (VKT). {Chapters 1 and 5, 10.2, 10.8}

'''Battery electric vehicles (BEVs) have lower lifecycle greenhouse gas (GHG) emissions than internal combustion engine vehicles (ICEVs) when BEVs are charged with low-carbon electricity (''' '''''high confidence''''' ''').''' Electromobility is being rapidly implemented in micro-mobility (e-autorickshaws, e-scooters, e-bikes), in transit systems, especially buses, and to a lesser degree, in personal vehicles. BEVs could also have the added benefit of supporting grid operations. The commercial availability of mature lithium-ion batteries (LIBs) has underpinned this growth in electromobility. As global battery production increases, unit costs are declining. Further efforts to reduce the GHG footprint of battery production, however, are essential for maximising the mitigation potential of BEVs. The continued growth of electromobility for land transport would entail investments in electric charging and related grid infrastructure. Electromobility powered by low-carbon electricity has the potential to rapidly reduce transport GHG and can be applied with multiple co-benefits, especially in developing countries. {10.3, 10.4, 10.8}

'''Land-based, long-range, heavy-duty trucks can be decarbonised through battery-electric haulage (including the use of electric road systems), complemented by hydrogen- and biofuel-based fuels in some contexts. These same technologies and expanded use of available electric rail systems can support rail decarbonisation (''' '''''medium confidence''''' ''').''' Initial deployments of battery-electric, hydrogen- and bio-based haulage are underway, and commercial operations of some of these technologies are considered feasible by 2030 ( ''medium confidence'' ). These technologies nevertheless face challenges regarding driving range, capital and operating costs, and infrastructure availability. In particular, fuel-cell durability, high energy consumption, and costs continue to challenge the commercialisation of hydrogen-based fuel-cell vehicles. Increased capacity for low-carbon hydrogen production would also be essential for hydrogen-based fuels to serve as an emissions reduction strategy ( ''high confidence'' ). (Box TS.15) {10.3, 10.4, 10.8}

'''Decarbonisation options for shipping and aviation still require R&amp;D, though advanced biofuels, ammonia, and synthetic fuels are emerging as viable options (''' '''''medium confidence''''' ''').''' Increased efficiency has been insufficient to limit the emissions from shipping and aviation, and natural gas-based fuels are expected to be inadequate to meet stringent decarbonisation goals for these segments ( ''high confidence'' ). High-energy density, low-carbon fuels are required, but they have not yet reached commercial scale. Advanced biofuels could provide low-carbon jet fuel ( ''medium confidence'' ). The production of synthetic fuels using low-carbon hydrogen with CO 2 captured through DACCS/BECCS could provide jet and marine fuels but these options still require demonstration at scale ( ''low confidence'' ). Ammonia produced with low-carbon hydrogen could also serve as a marine fuel ( ''medium confidence'' ). Deployment of these fuels requires reductions in production costs. (Figure TS.14) {10.2, 10.3, 10.4, 10.5, 10.6, 10.8}

<div id="_idContainer047" class="Basic-Text-Frame"></div>

[[File:7266b02cf4a09554403cbd952bb821d7 IPCC_AR6_WGIII_Figure_TS_14.png]]

'''Figure TS.1''' '''4 |''' '''Mitigation options and enabling conditions for transport. ‘Niche’ scale includes strategies that still require innovation.''' {Figure 10.22} ASI: Avoid-Shift-Improve; TRL: technology readiness level.

'''Scenarios from bottom-up and top-down models indicate that, without intervention, CO''' 2 '''emissions from transport could grow in the range of 16% and 50% by 2050 (''' '''''medium confidence''''' ''').''' The scenarios literature projects continued growth in demand for freight and passenger services, particularly in developing countries in Africa and Asia ( ''high confidence'' ). This growth is projected to take place across all transport modes. Increases in demand notwithstanding, scenarios that limit warming to 1.5°C degree with no or limited overshoot suggest that a 59% reduction (42–68% interquartile range) in transport-related CO 2 emissions by 2050, compared to modelled 2020 levels is required. While many global scenarios place greater reliance on emissions reduction in sectors other than transport, a quarter of the 1.5°C scenarios describe transport-related CO 2 emissions reductions in excess of 68% (relative to modelled 2020 levels) ( ''medium confidence'' ). Illustrative Mitigation Pathways IMP-Ren and IMP-LD (TS 4.2) describe emission reductions of 80% and 90% in the transport sector, respectively, by 2050. Transport-related emission reductions, however, may not happen uniformly across regions. For example, transport emissions from the Developed Countries, and Eastern Europe and West Central Asia countries decrease from 2020 levels by 2050 across all scenarios limiting global warming to 1.5°C by 2100, but could increase in Africa, Asia and Pacific (APC), Latin America and Caribbean, and the Middle East in some of these scenarios. {10.7}

'''The scenarios literature indicates that fuel and technology shifts are crucial in reducing carbon emissions to meet temperature goals (''' '''''high confidence''''' ''').''' In general terms, electrification tends to play the key role in land-based transport, but biofuels and hydrogen (and derivatives) could play a role in decarbonisation of freight in some contexts. Biofuels and hydrogen (and derivatives) are expected to be more prominent in shipping and aviation. The shifts towards these alternative fuels must occur alongside shifts towards clean technologies in other sectors. {10.7}

'''There is a growing awareness of the need to plan for the significant expansion of low-carbon energy infrastructure, including low-carbon power generation and hydrogen production, to support emissions reductions in the transport sector (''' '''''high confidence''''' ''').''' Integrated energy planning and operations that take into account energy demand and system constraints across all sectors (transport, buildings, and industry) offer the opportunity to leverage sectoral synergies and avoid inefficient allocation of energy resources. Integrated planning of transport and power infrastructure would be particularly useful in developing countries where ‘greenfield’ development doesn’t suffer from constraints imposed by legacy systems. {10.3, 10.4, 10.8}

'''The deployment of low-carbon aviation and shipping fuels that support decarbonisation of the transport sector could require changes to national and international governance structures (''' '''''medium confidence''''' ''').''' The UNFCCC does not specifically cover emissions from international shipping and aviation. Reporting emissions from international transport is at the discretion of each country. While the International Civil Aviation Organization (ICAO) and International Maritime Organization (IMO) have established emissions reductions targets, only strategies to improve fuel efficiency and demand reductions have been pursued, and there has been minimal commitment to new technologies. {10.5, 10.6, 10.7}

'''There are growing concerns about resource availability, labour rights, non-climate environmental impacts, and costs of critical minerals needed for lithium-ion batteries (''' '''''medium confidence''''' ''').''' Emerging national strategies on critical minerals and the requirements from major vehicle manufacturers are leading to new, more geographically diverse mines. The standardisation of battery modules and packaging within and across vehicle platforms, as well as increased focus on design for recyclability are important. Given the high degree of potential recyclability of lithium-ion batteries, a nearly closed-loop system in the future could mitigate concerns about critical mineral issues ( ''medium confidence'' ). {10.3, 10.8}

'''Legislated climate strategies are emerging at all levels of government, and together with pledges for personal choices, could spur the deployment of demand- and sup''' '''ply-sid''' '''e transport mitigation strategies (''' '''''medium confidence''''' ''').''' At the local level, legislation can support local transport plans that include commitments or pledges from local institutions to encourage behaviour change by adopting an organisational culture that motivates sustainable behaviour with inputs from the creative arts. Such institution-led mechanisms could include bike-to-work campaigns, free transport passes, parking charges, or eliminating car benefits. Community-based solutions such as ''solar sharing'' , ''community charging'' , and ''mobility as a service'' can generate new opportunities to facilitate low-carbon transport futures. At the regional and national levels, legislation can include vehicle and fuel efficiency standards, R&amp;D support, and large-scale investments in low-carbon transport infrastructure. (Figure TS.14) {10.8, Chapter 15}

<div id="TS.5.4" class="h2-container"></div>

<span id="ts.5.4-buildings"></span>
=== TS.5.4 Buildings ===

<div id="h2-6-siblings" class="h2-siblings"></div>

'''Global GHG emissions from buildings were 12 GtCO''' 2 '''-eq in 2019, equivalent to 21% of global GHG emissions. Of this, 57% (6.8 GtCO''' 2 '''-eq) were indirect emissions from off-site generation of electricity and heat, 24% (2.9 GtCO''' 2 '''-eq) were direct emissions produced on-site and 18% (2.2 GtCO''' 2 '''-eq) were embodied emissions from the production of cement and steel used in buildings (''' '''''high confidence''''' ''').''' Most building-sector emissions are CO 2 . Final energy demand from buildings reached 128 EJ globally in 2019 (around 31% of global final energy demand), and electricity demand from buildings was slightly above 43 EJ globally (around 18% of global electricity demand). Residential buildings consumed 70% (90 EJ) of the global final energy demand from buildings. Over the period 1990–2019, global CO 2 emissions from buildings increased by 50%, global final energy demand from buildings grew by 38%, and global final electricity demand increased by 161%. {9.3}

'''In most regions, historical improvements in efficiency have been approximately matched by growth in floor area per capita (''' '''''high confidence''''' ''').''' At the global level, building-specific drivers of GHG emissions include: (i) population growth, especially in developing countries; (ii) increasing floor area per capita, driven by the increasing size of dwellings while the size of households kept decreasing, especially in developed countries; (iii) the inefficiency of newly constructed buildings, especially in developing countries, and the low renovation rates and low ambition level in developed countries when existing buildings are renovated; (iv) the increase in use, number and size of appliances and equipment, especially information and communication technologies (ICT) and cooling, driven by income; and, (v) the continued reliance on carbon-intensive electricity and heat. These factors taken together are projected to continue driving increased GHG emissions in the building sector in the future. {9.3, 9.6, 9.9}

'''Building-sector GHG emissions were assessed using the Sufficiency, Efficiency, Renewable (SER) framework. Sufficiency measures tackle the causes of GHG emissions by limiting the demand for energy and materials over the lifecycle of buildings and appliances (''' '''''high confidence''''' ''').''' In [https://www.ipcc.ch/chapters/chapter-9 Chapter 9] of this report, ''sufficiency'' differs from ''efficiency'' : ''sufficiency'' is about long-term actions driven by non-technological solutions, which consume less energy in absolute terms; ''efficiency'' , in contrast is about continuous short-term marginal technological improvements. Sufficiency policies are a set of measures and daily practices that avoid demand for energy, materials, land and water while delivering human well-being-for-all within planetary boundaries. Use of the SER framework aims to reduce the cost of constructing and using buildings without reducing occupants’ well-being and comfort. {9.1, 9.4, 9.5, 9.9}

'''Sufficiency interventions do not consume energy during the use phase of buildings and do not require maintenance nor replacement over the lifetime of buildings.''' Density, compacity, bioclimatic design to optimise the use of nature-based solutions, multi-functionality of space through shared space and to allow for adjusting the size of buildings to the evolving needs of households, circular use of materials and repurposing unused existing buildings to avoid using virgin materials, optimisation of the use of buildings through lifestyle changes, use of the thermal mass of buildings to reduce thermal needs, and moving from ownership to usership of appliances, are among the sufficiency interventions implemented in leading municipalities ( ''high confidence'' ). At a global level, up to 17% of the mitigation potential in the buildings sector could be captured by 2050 through sufficiency interventions ( ''medium confidence'' ). (Figure TS.15) {9.2, 9.3, 9.4, 9.5, 9.9}

<div id="_idContainer051" class="Basic-Text-Frame"></div>

[[File:2db32aa3aa4ac3af4aea3398bfa209a6 IPCC_AR6_WGIII_Figure_TS_15.png]]

'''Figure TS.''' '''15: Decompositions of changes in historical residential energy emissions 1990–2019, changes in emissions projected by baseline scenarios for 2020–2050, and differences between scenarios in 2050 using scenarios from three models: IEA, IMAGE, and RECC.''' RECC-LED data for '''(a)''' global, and '''(b)''' for nine world regions, include only space heating and cooling and water heating in residential buildings. Emissions are decomposed using the equation, which shows changes in driver variables of population, sufficiency (floor area per capita), efficiency (final energy per floor area), and renewables (GHG emissions per final energy). ‘Renewables’ is a summary term describing changes in GHG intensity of energy supply. Emission projections to 2050, and differences between scenarios in 2050, demonstrate mitigation potentials from the dimensions of the SER framework realised in each model scenario. In most regions, historical improvements in efficiency have been approximately matched by growth in floor area per capita. Implementing sufficiency measures that limit growth in floor area per capita, particularly in developed regions, reduces the dependence of climate mitigation on technological solutions. {Figure 9.5, Box 9.2}

'''The potential associated with sufficiency measures, as well as the replacement of appliances, equipment and lights by efficient ones, is below zero cost (''' '''''high confidence''''' ''').''' The construction of high-performance buildings is expected to become a business-as-usual technology by 2050 with costs below USD20 tCO ''2'' ''–1'' in developed countries and below USD100 tCO ''2'' ''–1'' in developing countries ( ''medium confidence'' ). For existing buildings, there have been many examples of deep retrofits where additional costs per CO ''2'' abated are not significantly higher than those of shallow retrofits. However, for the whole building stock they tend to be in cost intervals of USD–200 tCO ''2'' ''–1'' and &gt;USD200 tCO ''2'' ''–1'' ( ''medium confidence'' ). Literature emphasises the critical role of the 2020–2030 decade in accelerating the learning of know-how and skills to reduce the costs and remove feasibility constraints for achieving high-efficiency buildings at scale and set the sector on the pathway to realise its full potential ( ''high confidence'' ). {9.3, 9.6, 9.9} .

'''The development, since AR5, of integrated approaches to the construction and retrofit of buildings has led to increasing the number of zero-energy or zero-carbon buildings in almost all climate zones.''' The complementarity and interdependency of measures leads to cost reductions, while optimising the mitigation potential achieved and avoiding the lock-in-effect ( ''medium confidence'' ). {9.6, 9.9}

'''The decarbonisation of buildings is constrained by multiple barriers and obstacles as well as limited finance flows (''' '''''high confidence''''' '''). The lack of institutional capacity, especially in developing countries, and appropriate governance structures slow down the decarbonisation of the global building stock (''' '''''medium confidence''''' ''').''' The building sector is highly heterogenous with many different building types, sizes, and operational uses. The sub-segment representing rented property faces principal/agent problems where the tenant benefits from the decarbonisation’s investment made by the landlord. The organisational context and the governance structure could trigger or hinder the decarbonisation of buildings. Global investment in the decarbonisation of buildings was estimated at USD164 billion in 2020. However, this is not enough by far to close the investment gap ( ''high confidence'' ). {9.9}

'''Policy packages could grasp the full mitigation potential of the global building stock. Building energy codes represent the main regulatory instrument to reduce emissions from both new and existing buildings (''' '''''high confidence''''' ''').''' The most advanced building energy codes include requirements on each of the three pillars of the SER framework in the ''use'' and ''construction'' phase of buildings. Building energy codes have proven to be effective if compulsory and combined with other regulatory instruments such as minimum energy performance standard for appliances and equipment, if the performance level is set at the level of the best available technologies in the market ( ''high confidence'' ). Market-based instruments such as carbon taxes with recycling of the revenues and personal or building carbon allowances could also contribute to fostering the decarbonisation of the building sector ( ''medium confidence'' ). {9.9}

'''Adapting buildings to future climate while ensuring well-being for all requires action. Expected heatwaves will inevitably increase cooling needs to limit the health impacts of climate change (''' '''''medium confidence''''' ''').''' Global warming will impact cooling and heating needs but also the performance, durability and safety of buildings, especially historical and coastal ones, through changes in temperature, humidity, atmospheric concentrations of CO 2 and chloride, and sea level rise. Adaptation measures to cope with climate change may increase the demand for energy and materials leading to an increase in GHG emissions if not mitigated. Sufficiency measures which anticipate climate change, and include natural ventilation, white walls, and nature-based solutions (e.g., green roofs) will decrease the demand for cooling. Shared cooled spaces with highly efficient cooling solutions are among the mitigation strategies which can limit the effect of the expected heatwaves on people’s health. {9.7, 9.8}

'''Well-designed and effectively implemented mitigation actions in the buildings sector have significant potential to help achieve the SDGs (''' '''''high confidence''''' ''').''' As shown in Figure TS.16, the impacts of mitigation actions in the building sector go far beyond the goal of climate action (SDG 13) and contribute to meeting 15 other SDGs. Mitigation actions in the building sector bring health gains through improved indoor air quality and thermal comfort, and have positive significant macro- and micro-economic effects, such as increased productivity of labour, job creation, reduced poverty, especially energy poverty, and improved energy security ( ''high confidence'' ). (Figure TS.29) {9.8}

<div id="_idContainer053" class="Basic-Text-Frame"></div>

[[File:da3c1db677ed89dd98801f5691d85a77 IPCC_AR6_WGIII_Figure_TS_16.png]]

'''Figure TS.''' '''16 |''' '''Contribution of building-sector mitigation policies to meeting Sustainable Development Goals.''' {Figure 9.18}

'''The COVID-19 pandemic emphasised the importance of buildings for human well-being and highlighted the inequalities in access for all to suitable, healthy buildings, which provide natural daylight and clean air to their occupants (''' '''''medium confidence''''' ''').''' Recent WHO health recommendations have also emphasise indoor air quality, preventive maintenance of centralised mechanical heating, ventilation, and cooling systems. There are opportunities for repurposing existing non-residential buildings, no longer in use due to the expected spread of teleworking triggered by the health crisis and enabled by digitalisation. (Box TS.14) {9.1}

<div id="TS.5.5" class="h2-container"></div>

<span id="ts.5.5-industry"></span>
=== TS.5.5 Industry ===

<div id="h2-7-siblings" class="h2-siblings"></div>

The industry chapter focuses on new developments since AR5 and emphasises the role of the energy-intensive and emissions-intensive basic materials industries in strategies for reaching net zero emissions. The Paris Agreement, the SDGs and the COVID-19 pandemic provide a new context for the evolution of industry and mitigation of industry greenhouse gas (GHG) emissions ( ''high confidence'' ). {11.1.1}

'''Net zero CO''' 2 '''industrial-sector emissions are possible but challenging (''' '''''high confidence''''' ''').''' Energy efficiency will continue to be important. Reduced materials demand, material efficiency, and circular economy solutions can reduce the need for primary production. Primary production options include switching to new processes that use low-to-zero GHG energy carriers and feedstocks (e.g., electricity, hydrogen, biofuels, and carbon dioxide capture and utilisation (CCU) to provide carbon feedstocks). Carbon capture and storage (CCS) will be required to mitigate remaining CO 2 emissions {11.3} . These options require substantial scaling up of electricity, hydrogen, recycling, CO ''2'' , and other infrastructure, as well as phase-out or conversion of existing industrial plants. While improvements in the GHG intensities of major basic materials have nearly stagnated over the last 30 years, analysis of historical technology shifts and newly available technologies indicate these intensities can be significantly reduced by mid-century. {11.2, 11.3, 11.4}

'''Industry-sector emissions have been growing faster since 2000 than emissions in any other sector, driven by increased basic materials extraction and production (''' '''''high confidence''''' ''').''' GHG emissions attributed to the industrial sector originate from fuel combustion, process emissions, product use and waste, which jointly accounted for 14.1 GtCO 2 -eq or 24% of all direct anthropogenic emissions in 2019, second behind the energy supply sector. Industry is a leading GHG emitter – 20 GtCO 2 -eq or 34% of global emissions in 2019 – if indirect emissions from power and heat generation are included. The share of emissions originating from direct fuel combustion is decreasing and was 7 GtCO 2 -eq, 50% of direct industrial emissions in 2019. {11.2.2}

'''Global material intensity – the in-use stock of manufactured capital in tonnes per unit of GDP – is increasing (''' '''''high confidence''''' ''').''' In-use stock of manufactured capital per capita has been growing faster than GDP per capita since 2000. Total global in-use stock of manufactured capital grew by 3.4% yr ''–1'' in 2000–2019. At the same time, per-capita material stocks in several developed countries have stopped growing, showing a decoupling from GDP per capita. {11.2.1, 11.3.1}

'''The demand for plastic has been growing most strongly since 1970 (''' '''''high confidence''''' ''').''' The current &gt;99% reliance on fossil feedstock, very low recycling, and high emissions from petrochemical processes is a challenge for reaching net zero emissions. At the same time, plastics are important for reducing emissions elsewhere, for example, light-weighting vehicles. There are as yet no shared visions for fossil-free plastics, but several possibilities. {11.4.1.3}

'''Scenario analyses show that significant reductions in global GHG emissions and even close to net zero emissions from GHG intensive industry (e.g., steel, plastics, ammonia, and cement) can be achieved by 2050 by deploying multiple available and emerging options (''' '''''medium confidence''''' ''').''' Significant reductions in industry emissions require a reorientation from the historic focus on important but incremental improvements (e.g., energy efficiency) to transformational changes in energy and feedstock sourcing, materials efficiency, and more circular material flows. {11.3, 11.4}

'''Key mitigation options such as materials efficiency, circular material flows and emerging primary processes, are not well represented in climate change scenario modelling and integrated assessment models (IAMs), albeit with some progress in recent years (''' '''''high confidence''''' ''').''' The character of these interventions (e.g., appearing in many forms across complex value chains, making cost estimates difficult) combined with the limited data on new fossil-free primary processes help explain why they are less represented in models than, for example, CCS. As a result, overall mitigation costs and the need for CCS may be overestimated. {11.4.2.1}

'''Electrification is emerging as a key mitigation option for industry (''' '''''high confidence''''' ''').''' Using electricity directly, or indirectly via hydrogen from electrolysis for high temperature and chemical feedstock requirements, offers many options to reduce emissions. It also can provide substantial grid-balancing services, for example, through electrolysis and storage of hydrogen for chemical process use or demand response. (Box TS.9) {11.3.5}

'''Carbon is a key building block in organic chemicals, fuels and materials and will remain important (''' '''''high confidence''''' ''').''' In order to reach net zero CO 2 emissions for the carbon needed in society (e.g., plastics, wood, aviation fuels, solvents, etc.), it is important to close the use loops for carbon and carbon dioxide through increased circularity with mechanical and chemical recycling, more efficient use of biomass feedstock with addition of low-GHG hydrogen to increase product yields (e.g., for biomethane and methanol), and potentially direct air capture of CO 2 as a new carbon source. {11.3, 11.4.1}

'''Production costs for very low to zero emissions basic materials may be high but the cost for final consumers and the general economy will be low (''' '''''medium confidence''''' ''').''' Costs and emissions reductions potential in industry, and especially heavy industry, are highly contingent on innovation, commercialisation, and market-uptake policies. Technologies exist to take all industry sectors to very low or zero emissions, but require five to fifteen years of intensive innovation, commercialisation, and policy to ensure uptake. Mitigation costs are in the rough range of USD50–150 tCO ''2'' -eq ''–'' 1 , with wide variation within and outside this band. This affects competitiveness and requires supporting policy. Although production cost increases can be significant, they translate to very small increases in the costs for final products, typically less than a few percent depending on product, assumptions, and system boundaries. (Figure TS.17) {11.4.1.5}

<div id="_idContainer055" class="Basic-Text-Frame"></div>

[[File:8b632d50284e779cc7cbe7333899570b IPCC_AR6_WGIII_Figure_TS_17.png]]

'''Figure TS.17''' ''': Potentials and costs for zero-carbon mitigation options for industry and basic materials.''' CIEl – carbon intensity of electricity for indirect emissions; EE – energy efficiency; ME – material efficiency; Circularity – material flows (clinker substituted by coal fly ash, blast furnace slag or other by-products and waste, steel scrap, plastic recycling, etc.); FeedCI – feedstock carbon intensity (hydrogen, biomass, novel cement, natural clinker substitutes); FSW+El – fuel switch and processes electrification with low-carbon electricity. Ranges for mitigation options are shown based on bottom-up studies for grouped technologies packages, not for single technologies. In circles, contribution to mitigation from technologies based on their readiness are shown for 2050 (2040) and 2070. Direct emissions include fuel combustion and process emissions. Indirect emissions include emissions attributed to consumed electricity and purchased heat. For basic chemicals, only methanol, ammonia and high-value chemicals are considered. Total for industry does not include emissions from waste. Negative mitigation costs for some options such as Circularity are not reflected. {Figure 11.13}

'''Several technological options exist for very low to zero emissions steel, but their uptake will require integrated material efficiency, recycling, and production decarbonisation policies (''' '''''high confidence''''' ''').''' Material efficiency can potentially reduce steel demand by up to 40% based on design for less steel use, long life, reuse, constructability, and low-contamination recycling. Secondary production through high-quality recycling must be maximised. Production decarbonisation will also be required, starting with the retrofitting of existing facilities for partial fuel switching (e.g., to biomass or hydrogen), CCU and CCS, followed by very low and zero emissions production based on high-capture CCS or direct hydrogen, or electrolytic iron-ore reduction followed by an electric arc furnace. {11.3.2, 11.4.1.1}

'''Several current and emerging options can significantly reduce cement and concrete emissions. Producer, user, and regulator education, as well as innovation and commercialisation policy are needed (''' '''''medium confidence''''' ''').''' Cement and concrete are currently overused because they are inexpensive, durable, and ubiquitous, and consumption decisions typically do not give weight to their production emissions. Basic material efficiency efforts to use only well-made concrete thoughtfully and only where needed (e.g., using right-sized, prefabricated components) could reduce emissions by 24–50% through lower demand for clinker. Cementitious material substitution with various materials (e.g., ground limestone and calcined clays) can reduce process calcination emissions by up to 50% and occasionally much more. Until a very low GHG emissions alternative binder to Portland cement is commercialised – which is not anticipated in the near to mid-term – CCS will be essential for eliminating the limestone calcination process emissions for making clinker, which currently represent 60% of GHG emissions in best-available technology plants. {11.3.2, 11.3.6, 11.4.1.2}

'''While several technological options exist for decarbonising the main industrial feedstock chemicals and their derivatives, the costs vary widely (''' '''''high confidence''''' ''').''' Fossil fuel-based feedstocks are inexpensive and still without carbon pricing, and their biomass- and electricity-based replacements are expected to be more expensive. The chemical industry consumes large amounts of hydrogen, ammonia, methanol, carbon monoxide, ethylene, propylene, benzene, toluene, and mixed xylenes and aromatics from fossil feedstock, and from these basic chemicals produces tens of thousands of derivative end-use chemicals. Hydrogen, biogenic or air-capture carbon, and collected plastic waste for the primary feedstocks can greatly reduce total emissions. Biogenic carbon feedstock is expected to be limited due to competing land uses. {11.4.1}

'''Light industry and manufacturing can be largely decarbonised through switching to low-GHG fuels (e.g., biofuels and hydrogen) and electricity (e.g., for electrothermal heating and heat pumps) (''' '''''high confidence''''' ''').''' Most of these technologies are already mature, for example for low-temperature heat, but a major challenge is the current low cost of fossil CH 4 and coal relative to low- and zero-GHG electricity, hydrogen, and biofuels. {11.4.1}

'''The pulp and paper industry has significant biogenic carbon emissions but relatively small fossil carbon emissions. Pulp mills have access to biomass residues and by-products and in paper mills the use of process heat at low to medium temperatures allows for electrification (''' '''''high confidence''''' ''').''' Competition for feedstock will increase if wood substitutes for building materials and petrochemicals feedstock. The pulp and paper industry can also be a source of biogenic carbon dioxide, carbon for organic chemicals feedstock, and for CDR using CCS. {11.4.1}

'''The geographical distribution of renewable resources has implications for industry (''' '''''medium confidence''''' ''').''' The potential for zero-emission electricity and low-cost hydrogen from electrolysis powered by solar and wind, or hydrogen from other very low emission sources, may reshape where currently energy- and emissions-intensive basic materials production is located, how value chains are organised, trade patterns, and what gets transported in international shipping. Regions with bountiful solar and wind resources, or low fugitive CH 4 co-located with CCS geology, may become exporters of hydrogen or hydrogen carriers such as methanol and ammonia, or home to the production of iron and steel, organic platform chemicals, and other energy-intensive basic materials. {11.2, 11.4, Box 11.1}

'''The level of policy maturity and experience varies widely across the mitigation options (''' '''''high confidence''''' ''').''' Energy efficiency is a well-established policy field with decades of experience from voluntary and negotiated agreements, regulations, energy auditing and demand-side management (DSM) programmes. In contrast, materials demand management and efficiency are not well understood and addressed from a policy perspective. Barriers to recycling that policy could address are often specific to the different material loops (e.g., copper contamination for steel and lack of technologies or poor economics for plastics) or waste-management systems. For electrification and fuel switching the focus has so far been mainly on innovation and developing technical supply-side solutions rather than creating market demand. {11.5.2, 11.6}

'''Industry has so far largely been sheltered from the impacts of climate policy and carbon pricing due to concerns about carbon leakage''' [[#footnote-007|26]] '''and reducing competitiveness (''' '''''high confidence''''' ''').''' New approaches to industrial development policy are emerging for a transition to net zero GHG emissions. The transition requires a clear direction towards net zero, technology development, market demand for low-carbon materials and products, governance capacity and learning, socially inclusive phase-out plans, as well as international coordination of climate and trade policies (see also TS.6.5). It requires comprehensive and sequential industrial policy strategies leading to immediate action as well as preparedness for future decarbonisation, governance at different levels (from international to local) and integration with other policy domains. {11.6}

<div id="TS.5.6" class="h2-container"></div>

<span id="ts.5.6-agriculture-forestry-other-land-uses-and-food-systems"></span>
=== TS.5.6 Agriculture, Forestry, Other Land Uses, and Food Systems ===

<div id="h2-8-siblings" class="h2-siblings"></div>

<div id="TS.5.6.1" class="h3-container"></div>

<span id="ts.5.6.1-agricultre-forestry-and-other-land-use-afolu"></span>
==== TS.5.6.1 Agricultre, Forestry, and Other Land Use (AFOLU) ====

<div id="h3-1-siblings" class="h3-siblings"></div>

'''The agriculture, forestry and other land use (AFOLU)''' [[#footnote-006|27]] '''sector encompasses managed ecosystems and offers significant mitigation opportunities while providing food, wood and other renewable resources as well as biodiversity conservation, provided the sector adapts to climate change.''' Land-based mitigation measures can reduce GHG emissions within the AFOLU sector, deliver CDR and provide biomass thereby enabling emission reductions in other sectors. [[#footnote-005|28]] The rapid deployment of AFOLU measures features in all pathways that limit global warming to 1.5°C. Where carefully and appropriately implemented, AFOLU mitigation measures are positioned to deliver substantial co-benefits and help address many of the wider challenges associated with land management. If AFOLU measures are deployed badly, when taken together with the increasing need to produce sufficient food, feed, fuel and wood, they may exacerbate trade-offs with the conservation of habitats, adaptation, biodiversity and other services. At the same time the capacity of the land to support these functions may be threatened by climate change ( ''high confidence'' ). {AR6 WGI Figure SPM.7; AR6 WGII, 7.1, 7.6}

'''The AFOLU sector, on average, accounted for 13–21% of global total anthropogenic GHG emissions in the period 2010–2019. At the same time managed and natural terrestrial ecosystems were a carbon sink, absorbing around one third of anthropogenic CO''' 2 '''emissions (''' '''''medium confidence''''' ''').''' Estimated anthropogenic net CO 2 emissions from AFOLU (based on bookkeeping models) result in a net source of +5.9 ± 4.1 GtCO 2 yr –1 between 2010 and 2019 with an unclear trend. Based on FAOSTAT or national GHG inventories, the net CO 2 emissions from AFOLU were 0.0 to +0.8 GtCO 2 yr –1 over the same period. There is a discrepancy in the reported CO 2 AFOLU emissions magnitude because alternative methodological approaches that incorporate different assumptions are used {7.2.2} . If the responses of all managed and natural land to both anthropogenic environmental change and natural climate variability, estimated to be a gross sink of –12.5 ± 3.2 GtCO 2 yr –1 for the period 2010–2019, are added to land-use emissions, then land overall constituted a net sink of –6.6 ± 5.2 GtCO 2 yr –1 in terms of CO 2 emissions ( ''medium confidence'' ). (Table TS.4) {7.2, Table 7.1}

Table TS.4 | Net anthropogenic emissions (annual averages for 2010–201 9 '''''a''''' ) from agriculture, forestry and other land use (AFOLU). For context, the net flux due to the natural response of land to climate and environmental change is also shown for CO 2 in column E. Positive values represent emissions, negative values represent removals. Due to different approaches to estimate anthropogenic fluxes, AFOLU CO 2 estimates in the table below are not directly comparable to LULUCF in national greenhouse gas inventories (NGHGIs).

{| class="wikitable"
|-
| colspan="6"| '''Anthropogenic'''

| '''Natural response'''

| '''Natural and anthropogenic'''

|-
| rowspan="2"| '''Gas'''

| rowspan="2"| '''Units'''

| '''AFOLU net anthropogenic emissions'''

| '''Non-AFOLU anthropogenic GHG emissions'''

| '''Total net anthropogenic emissions (AFOLU and non-AFOLU) by gas'''

| '''AFOLU as a % of total net anthropogenic emissions by gas'''

| '''Natural land sinks including natural response of land to anthropogenic environmental change and climate variability'''

| '''Net-land atmosphere CO''' 2 '''flux (i.e., anthropogenic AFOLU and natural fluxes across entire land surface)'''

|-
| '''A'''

| '''B'''

| '''C = A + B'''

| '''D = (A/C) *100'''

| '''E'''

| '''F = A + E'''

|-
| '''CO''' 2

| GtCO 2 -eq yr –1

| 5.9 ± 4.1 (bookkeeping

models, managed

soils and pasture).

0 to 0.8 (NGHGI/

FAOSTAT data)

| 36.2 ± 2.9

| 42.0 ± 29.0

| 14%

| –12.5 ± 3.2

| –6.6 ± 4.6

|-
| rowspan="2"| '''CH''' 4

| MtCH 4 yr – 1

| 157.0 ± 47.1

| 207.5 ± 62.2

| 364.4 ± 109.3

|
|-
| GtCO 2 -eq yr –1

| 4.2 ± 1.3

| 5.9 ± 1.8

| 10.2 ± 3.0

| 41%

|
|-
| rowspan="2"| '''N''' 2 '''O'''

| MtN 2 O yr –1

| 6.6 ± 4.0

| 2.8 ± 1.7

| 9.4 ± 5.6

|
|-
| GtCO 2 -eq yr –1

| 1.8 ± 1.1

| 0.8 ± 0.5

| 2.6 ± 1.5

| 69%

|
|-
| '''Total'''

| GtCO 2 -eq yr –1

| 11.9 ± 4.4

(CO 2 component considers bookkeeping models only)

| 44 ± 3.4

| 55.9 ± 6.1

| 21%

|
|}

a Estimates are given for 2019 as this is the latest date when data are available for all gases, consistent with [https://www.ipcc.ch/chapters/chapter-2 Chapter 2] of this report. Positive fluxes are emission from land to the atmosphere. Negative fluxes are removals. For all Table footnotes see Table 7.1. {Table 7.1}

'''Land-use change drives net AFOLU CO''' 2 '''emission fluxes. The rate of deforestation, which accounts for 45% of total AFOLU emissions, has generally declined, while global tree cover and global forest-growing stock levels are''' '''''likely''''' '''increasing (''' '''''medium confidence''''' ''').''' There are substantial regional differences, with losses of carbon generally observed in tropical regions and gains in temperate and boreal regions. Agricultural CH 4 and N 2 O emissions are estimated to average 157 ± 47.1 MtCH 4 yr –1 and 6.6 ± 4.0 MtN 2 O yr –1 or 4.2 ± 1.3 and 1.8 ± 1.1 GtCO 2 -eq yr –1 (using IPCC AR6 GWP100 values for CH 4 and N 2 O) respectively between 2010 and 2019 {7.2.1, 7.2.3} . AFOLU CH 4 emissions continue to increase ''',''' the main source of which is enteric fermentation from ruminant animals. Similarly, AFOLU N 2 O emissions are increasing, dominated by agriculture, notably from manure application, nitrogen deposition, and nitrogen fertiliser use ( ''high confidence'' ). In addition to being a net carbon sink and source of GHG emissions, land plays an important role in climate through albedo effects, evapotranspiration, and aerosol loading through emissions of volatile organic compounds (VOCs). The combined role of CH ''4'' , N 2 O and aerosols in total climate forcing, however, is unclear and varies strongly with bioclimatic region and management practice. {2.4.2.5, 7.2, 7.3}

'''The AFOLU sector offers significant near-term mitigation potential at relatively low cost and can provide 20–30% of the 2050 emissions reduction described in scenarios that limit warming to 2°C (&gt;67%) or lower (''' '''''high evidence''''' ''''', medium agreement''''' ''').''' The AFOLU sector can provide 20–30% (interquartile range) of the global mitigation needed for a 1.5°C or 2°C pathway towards 2050, though there are highly variable mitigation strategies for how AFOLU potential can be deployed for achieving climate targets {Illustrative Mitigation Pathways in 7.5} . The estimated economic (&lt;USD100 tCO 2 -eq –1 ) AFOLU sector mitigation potential is 8 to 14 GtCO 2 -eq yr –1 between 2020–2050, with the bottom end of this range representing the mean from IAMs and the upper end representing the mean estimate from global sectoral studies. The economic potential is about half of the technical potential from AFOLU, and about 30–50% could be achieved under USD20 tCO ''2'' -eq ''–'' 1 {7.4} . The implementation of robust measurement, reporting and verification processes is paramount to improving the transparency of changes in land carbon stocks and this can help prevent misleading assumptions or claims on mitigation. {7.1, 7.4, 7.5}

'''Between 2020 and 2050, mitigation measures in forests and other natural ecosystems provide the largest share of the AFOLU mitigation potential (up to USD100 tCO''' 2 '''-eq''' –1 '''), followed by agriculture and demand-side measures (''' '''''high confidence''''' ''').''' In the global sectoral studies, the protection, improved management, and restoration of forests, peatlands, coastal wetlands, savannas and grasslands have the potential to reduce emissions and/or sequester 7.3 mean (3.9–13.1) GtCO 2 -eq yr –1 . Agriculture provides the second largest share of the mitigation potential, with 4.1 (1.7–6.7) GtCO ''2'' -eq yr ''–'' 1 (up to USD100 tCO 2 -eq –1 ) from cropland and grassland soil carbon management, agroforestry, use of biochar, improved rice cultivation, and livestock and nutrient management. Demand-side measures including shifting to sustainable healthy diets, reducing food waste, building with wood, biochemicals, and bio-textiles, have a mitigation potential of 2.2 (1.1–3.6) GtCO ''2'' -eq yr –1 . Most mitigation options are available and ready to deploy. Emissions reductions can be achieved relatively quickly, whereas CDR needs upfront investment. Sustainable intensification in agriculture, shifting diets, and reducing food waste could enhance efficiencies and reduce agricultural land needs, and are therefore critical for enabling supply-side measures such as reforestation, restoration, as well as decreasing CH 4 and N 2 O emissions from agricultural production. In addition, emerging technologies (e.g., vaccines or CH 4 inhibitors) have the potential to substantially increase the CH 4 mitigation potential beyond current estimates. AFOLU mitigation is not only relevant in countries with large land areas. Many smaller countries and regions, particularly with wetlands, have disproportionately high levels of AFOLU mitigation potential density. {7.4, 7.5}

'''The economic and political feasibility of implementing AFOLU mitigation measures is hampered by persistent barriers. Assisting countries to overcome barriers will help to achieve significant short-term mitigation (''' '''''medium confidence''''' ''').''' Finance forms a critical barrier to achieving these gains as currently mitigation efforts rely principally on government sources and funding mechanisms which do not provide sufficient resources to enable the economic potential to be realised. Differences in cultural values, governance, accountability and institutional capacity are also important barriers. Climate change itself could reduce the mitigation potential from the AFOLU sector, although an increase in the capacity of natural sinks could occur despite changes in climate ( ''medium'' ''confidence'' ) {AR6 WGI Figure SPM.7 and Sections 7.4 and 7.6} . The continued loss of biodiversity makes ecosystems less resilient to climate change extremes and this may further jeopardise the achievement of the AFOLU mitigation potentials indicated in this chapter ( ''high confidence'' ). (Box TS.15) {7.6}

'''The provision of biomass for bioenergy (with/without BECCS) and other bio-based products represents an important share of the total mitigation potential associated with the AFOLU sector, though these mitigation effects accrue to other sectors (''' '''''high confidence''''' ''').''' Recent estimates of the technical bioenergy potential, when constrained by food security and environmental considerations, are within the ranges 5–50 and 50–250 EJ yr –1 by 2050 for residues and dedicated biomass production systems, respectively. [[#footnote-004|29]] (TS.5.7) {7.4, 12.3}

'''Bioenergy is the most land-intensive energy option, but total land occupation of other renewable energy options can also become significant in high deployment scenarios. While not as closely connected to the AFOLU sector as bioenergy, other renewable energy options can influence AFOLU activities in both synergistic and detrimental ways (''' '''''high confidence''''' ''').''' The character of land occupation, and associated impacts, vary considerably among mitigation options and also for the same option depending on geographic location, scale, system design and deployment strategy. Land occupation can be large uniform areas, for example, reservoir hydropower dams and tree plantations, and more distributed occupation that is integrated with other land uses, for example, wind turbines and agroforestry in agriculture landscapes. Deployment can be partly decoupled from additional land use, for example, use of organic waste and residues and integration of solar PV into buildings and other infrastructure ( ''high confidence'' ). Wind and solar power can coexist with agriculture in beneficial ways ( ''medium confidence'' ). Indirect land occupation includes new agriculture areas following displacement of food production with bioenergy plantations and expansion of mining activities providing minerals required for manufacture of EV batteries, PV, and wind power. {7.4, 12.5}

'''The deployment of land-based mitigation measures can provide co-benefits, but there are also risks and trade-offs from inappropriate land management (''' '''''high confidence''''' '''). Such risks can best be managed if AFOLU mitigation is pursued in response to the needs and perspectives of multiple stakeholders to achieve outcomes that maximise synergies while limiting trade-offs (''' '''''medium confidence''''' ''').''' The results of implementing AFOLU measures are often variable and highly context-specific. Depending on local conditions (e.g., ecosystem, climate, food system, land ownership) and management strategies (e.g., scale, method), mitigation measures can positively or negatively affect biodiversity, ecosystem functioning, air quality, water availability and quality, soil productivity, rights infringements, food security, and human well-being. The agriculture and forestry sectors can devise management approaches that enable biomass production and use for energy in conjunction with the production of food and timber, thereby reducing the conversion pressure on natural ecosystems ( ''medium confidence'' ). Mitigation measures addressing GHGs may also affect other climate forcers such as albedo and evapotranspiration. Integrated responses that contribute to mitigation, adaptation, and other land challenges will have greater likelihood of being successful ( ''high confidence'' ); measures which provide additional benefits to biodiversity and human well-being are sometimes described as ‘Nature-based Solutions’. {7.1, 7.4, 7.6, 12.4, 12.5}

'''AFOLU mitigation measures have been well understood for decades but deployment remains slow, and emissions trends indicate unsatisfactory progress despite beneficial contributions to global emissions reduction from forest-related options (''' '''''high confidence''''' ''').''' Globally, the AFOLU sector has so far contributed modestly to net mitigation, as past policies have delivered about 0.65 GtCO 2 yr –1 of mitigation during 2010–2019 or 1.4% of global gross emissions. The majority (&gt;80%) of emission reduction resulted from forestry measures. Although the mitigation potential of AFOLU measures is large from a biophysical and ecological perspective, its feasibility is hampered by lack of institutional support, uncertainty over long-term additionality and trade-offs, weak governance, fragmented land ownership, and uncertain permanence effects. Despite these impediments to change, AFOLU mitigation options are demonstrably effective and with appropriate support can enable rapid emission reductions in most countries. {7.4, 7.6}

'''Concerted, rapid and sustained effort by all stakeholders, from policymakers and investors to land owners and managers is a pre-requisite for achieving high levels of mitigation in the AFOLU sector (''' '''''high confidence''''' ''').''' To date USD0.7 billion yr ''–1'' is estimated to have been spent on AFOLU mitigation. This is well short of the more than USD400 billion yr ''–1'' that is estimated to be necessary to deliver the up to 30% of global mitigation effort envisaged in deep mitigation scenarios ( ''medium confidence'' ). This estimate of the global funding requirement is smaller than current subsidies provided to agriculture and forestry. A gradual redirection of existing agriculture and forestry subsidies would greatly advance mitigation. Effective policy interventions and national (investment) plans as part of NDCs, specific to local circumstances and needs, are urgently needed to accelerate the deployment of AFOLU mitigation options. These interventions are effective when they include funding schemes and long-term consistent support for implementation with governments taking the initiative together with private funders and non-state actors. {7.6}

'''Realising the mitigation potential of the AFOLU sector depends strongly on policies that directly address emissions and drive the deployment of land-based mitigation options, consistent with carbon prices in deep mitigation scenarios (''' '''''high confidence''''' ''').''' Examples of successful policies and measures include establishing and respecting tenure rights and community forestry, improved agricultural management and sustainable intensification, biodiversity conservation, payments for ecosystem services, improved forest management and wood-chain usage, bioenergy, voluntary supply chain management efforts, consumer behaviour campaigns, private funding and joint regulatory efforts to avoid, for example, leakage. The efficacy of different policies, however, will depend on numerous region-specific factors. In addition to funding, these factors include governance, institutions, long-term consistent execution of measures, and the specific policy setting. While the governance of land-based mitigation can draw on lessons from previous experience with regulating biofuels and forest carbon, integrating these insights requires governance that goes beyond project-level approaches emphasising integrated land-use planning and management within the frame of the Sustainable Development Goals. {7.4, Box 7.2, 7.6}

'''Addressing the many knowledge gaps in the development and testing of AFOLU mitigation options can rapidly advance the likelihood of achieving sustained mitigation (''' '''''high''''' '''''confidence''''' ''').''' Research priorities include improved quantification of anthropogenic and natural GHG fluxes and emissions modelling, better understanding of the impacts of climate change on the mitigation potential, permanence and additionality of estimated mitigation actions, and improved (real-time and cheap) measurement, reporting and verification. There is a need to include a greater suite of mitigation measures in IAMs, informed by more realistic assessments that take into account local circumstances and socio-economic factors and cross-sector synergies and trade-offs. Finally, there is a critical need for more targeted research to develop appropriate country-level, locally specific, policy and land-management response options. These options could support more specific NDCs with AFOLU measures that enable mitigation while also contributing to biodiversity conservation, ecosystem functioning, livelihoods for millions of farmers and foresters, and many other SDGs. {7.7, Figure 17.1}

<div id="TS.5.6.2" class="h3-container"></div>

<span id="ts.5.6.2-food-systems"></span>
==== TS.5.6.2 Food Systems ====

<div id="h3-1-siblings" class="h3-siblings"></div>

'''Realising the full mitigation potential from the food system requires change at all stages from producer to consumer and waste management, which can be facilitated through integrated policy packages (''' '''''high confidence''''' ''').''' Food systems are associated with 23–42% of global GHG emissions, while there is still widespread food insecurity and malnutrition. Absolute GHG emissions from food systems increased from 14 to 17 GtCO 2 -eq yr –1 in the period 1990–2018. Both supply- and demand-side measures are important to reduce the GHG intensity of food systems. Integrated food policy packages based on a combination of market-based, administrative, informative, and behavioural policies can reduce cost compared to uncoordinated interventions, address multiple sustainability goals, and increase acceptance across stakeholders and civil society ( ''limited evidence'' , ''medium agreement'' ) ''.'' Food systems governance may be pioneered through local food policy initiatives complemented by national and international initiatives, but governance on the national level tends to be fragmented, and thus has limited capacity to address structural issues like inequities in access. (Figure TS.18, Table TS.5, Table TS.6) {7.2, 7.4, 12.4}

[[File:a1089d0ce8d599427cec711ba4074362 IPCC_AR6_WGIII_Figure_TS_18.png]]
'''Figure TS.18''' '''|''' '''Food-system GHG emissions from the agriculture, and land use, land-use change and forestry (LULUCF), waste, and energy and industry sectors.''' {Figure 12.5}

'''Table TS''' '''.5 |''' '''Food system mitigation opportunities.'''

{| class="wikitable"
|-
| colspan="2"| '''Food system mitigation options (I: incremental; T: transformative)'''

| '''Direct and indirect effect on GHG mitigation (+/0/–)''' a

| '''Co-benefits/adverse effects''' b

|-
| rowspan="5"| Food from agriculture, aquaculture and fisheries

| (I) Dietary shift, in particular increased share of plant-based protein sources

| D+ ↓ GHG footprint

| A+ Animal welfare

L+ Land sparing

H+ Good nutritional properties, potentially ↓ risk from zoonotic diseases, pesticides and antibiotics

|-
| (I/T) Digital agriculture

| D+ ↑ logistics

| L+ Land sparing

R+ ↑ resource-use efficiencies

|-
| (T) Gene technology

| D+ ↑ productivity or efficiency

| H+ ↑ nutritional quality

E0 ↓ use of agrochemicals; ↑ probability of off-target impacts

|-
| (I) Sustainable intensification Land-use optimisation

| D+ ↓ GHG footprint

E0 Mixed effects

| L+ Land sparing

R– Might ↑ pollution/biodiversity loss

|-
| (I) Agroecology

| D+ ↓ GHG/area, positive micro-climatic effects

E+ ↓ energy, possibly ↓ transport FL+ Circular approaches

| E+ Focus on co-benefits/ecosystem services

R+ Circular, ↑ nutrient and water use efficiencies

|-
| Controlled environment agriculture

| (T) Soil-less agriculture

| D+ ↑ productivity, weather independent

FL+ Harvest on demand

E– Currently ↑ energy demand, but ↓ transport, building spaces can be used for renewable energy

| R+ Controlled loops ↑ nutrient- and water-use efficiency

L+ Land sparing

H+ Crop breeding can be optimised for taste and/or nutritional quality

|-
| rowspan="4"| Emerging food production technologies

| (T) Insects

| D0 Good feed conversion efficiency

FW+ Can be fed on food waste

| H0 Good nutritional qualities but attention to allergies and food safety issues required

|-
| (I/T) Algae and bivalves

| D+ ↓ GHG footprints

| A+ Animal welfare

L+ Land sparing

H+ Good nutritional qualities; risk of heavy-metal and pathogen contamination

R+ Biofiltration of nutrient-polluted waters

|-
| (I/T) Plant-based alternatives to animal-based food products

| D+ No emissions from animals, ↓ inputs for feed

| A+ Animal welfare

L+ Land sparing

H+ Potentially ↓ risk from zoonotic diseases, pesticides and antibiotics; but ↑ processing demand

|-
| (T) Cellular agriculture (including cultured meat, microbial protein)

| D+ No emissions from animals, high protein conversion efficiency

E– ↑ energy need

FLW+ ↓ food loss and waste

| A+ Animal welfare

R+ ↓ emissions of reactive nitrogen or other pollutants

H0 Potentially ↓ risk from zoonotic diseases, pesticides and antibiotics; ↑ research on safety aspects needed

|-
| rowspan="4"| Food processing and packaging

| (I) Valorisation of by-products, FLW logistics and management

| M+ Substitution of bio-based materials

FL+ ↓ of food losses

|
|-
| (I) Food conservation

| FW+ ↓ of food waste

E0 ↑ energy demand but also energy savings possible (e.g., refrigeration, transport)

|
|-
| (I) Smart packaging and other technologies

| FW+ ↓ of food waste

M0 ↑ material demand and ↑ material efficiency

E0 ↑ energy demand; energy savings possible

| H+ Possibly ↑ freshness/reduced food safety risks

|-
| (I) Energy efficiency

| E+ ↓ energy

|
|-
| rowspan="5"| Storage and distribution

| (I) Improved logistics

| D+ ↓ transport emissions

FL+ ↓ losses in transport

FW– Easier access to food could ↑ food waste

|
|-
| (I) Specific measures to reduce food waste in retail and food catering

| FW+ ↓ of food waste

E+ ↓ downstream energy demand

M+ ↓ downstream material demand

|
|-
| (I) Alternative fuels/transport modes

| D+ ↓ emissions from transport

|
|-
| (I) Energy efficiency

| E+ ↓ energy in refrigeration, lightening, climatisation

|
|-
| (I) Replacing refrigerants

| D+ ↓ emissions from the cold chain

|
|}

a Direct and indirect GHG effects: D – direct emissions except emissions from energy use, E – energy demand, M – material demand, FL – food losses, FW – food waste; direction of effect on GHG mitigation: (+) increased mitigation, (0) neutral, (–) decreased mitigation.

b Co-benefits/adverse effects: H – health aspects, A – animal welfare, R – resource use, L – land demand, E – ecosystem services; (+) co-benefits, (–) adverse effects. {Table 12.8}

'''Table TS.''' '''6 |''' '''Assessment of food system policies targeting (post-farm gate) food-chain actors and consumers.'''

{| class="wikitable"
|-
!
! ''Level G: global/multinational; N: national; L: local''

! ''Transformative potential''

! ''Environmental effectiveness''

! ''Feasibility''

! ''Distributional effects''

! ''Cost''

! ''Co-benefits'' a ''and adverse side effect''

! ''Implications for coordination, coherence and consistency in policy package'' b

|-
| '''Integrated food policy packages'''

| '''NL'''

|
| ''can be controlled''

| ''cost efficient''

| '''+ balanced, addresses multiple sustainability goals'''

| Reduces cost of uncoordinated interventions; increases acceptance across stakeholders and civil society ( ''robust evidence'' , ''high agreement'' )

|-
| Taxes on food products

| GN

|
| ''regressive''

| low # 1

| ''– unintended substitution effects''

| High enforcing effect on other food policies; higher acceptance if compensation or hypothecated taxes ( ''medium evidence'' , ''high agreement'' )

|-
| rowspan="2"| GHG taxes on food

| rowspan="2"| GN

| rowspan="2"|
| rowspan="2"| ''regressive''

| rowspan="2"| low # 2

| ''– unintended substitution effects''

| rowspan="2"| Supportive, enabling effect on other food policies, agricultural/fishery policies; requires changes in power distribution and trade agreements ( ''medium evidence'' , ''medium agreement'' )

|-
| + high spillover effect

|-
| rowspan="2"| Trade policies

| rowspan="2"| G

| rowspan="2"|
| rowspan="2"| impacts global distribution

| rowspan="2"| complex effects

| + counters leakage effects

| rowspan="2"| Requires changes in existing trade agreements ( ''medium'' ''evidence'' , ''high agreement'' )

|-
| +/– effects on market structure and jobs

|-
| Investment into research and innovation

| GN

|
| none

| medium

| + high spillover effect + converging with digital society

| Can fill targeted gaps for coordinated policy packages (e.g., monitoring methods) ( ''robust evidence'' , ''high agreement'' )

|-
| Food and marketing regulations

| N

|
| low

|
| Can be supportive; might be supportive to realise innovation; voluntary standards might be less effective ( ''medium evidence'' , ''medium agreement'' )

|-
| Organisational-level procurement policies

| NL

|
| low

| + can address multiple sustainability goals

| Enabling effect on other food policies; reaches large share of population ( ''medium evidence'' , ''high agreement'' )

|-
| Sustainable food-based dietary guidelines

| GNL

|
| none

| low

| + can address multiple sustainability goals

| Little attention so far on environmental aspects; can serve as benchmark for other policies (labels, food formulation standards, etc.) ( ''medium evidence'' , ''medium agreement'' )

|-
| Food labels/ information

| GNL

|
| education level relevant

| low

| + empowers citizens

+ increases awareness

+ multiple objectives

| Effective mainly as part of a policy package; incorporation of other objectives (e.g., animal welfare, fair trade); higher effect if mandatory ( ''medium evidence'' , ''medium'' ''agreement'' )

|-
| Nudges

| NL

|
| none

| low

| + possibly counteracting information deficits in population subgroups

| High enabling effect on other food policies ( ''medium'' ''evidence'' , ''high agreement'' )

|}

Effect of measures:   negative   none/unclear   slightly positive   positive 

Notes: #1 Minimum level to be effective 20% price increase; #2 Minimum level to be effective USD50–80 tCO 2 -eq. a In addition, all interventions are assumed to address health and climate change mitigation. b Requires coordination between policy areas, participation of stakeholders, transparent methods and indicators to manage trade-offs and prioritisation between possibly conflicting objectives; and suitable indicators for monitoring and evaluation against objectives.

'''Diets high in plant protein and low in meat and dairy are associated with lower GHG emissions (''' '''''high confidence''''' ''').''' Ruminant meat shows the highest GHG intensity. Beef from dairy systems has lower emissions intensity than beef from beef herds (8–23 and 17–94 kgCO ''2'' -eq (100 g protein) ''–1'' , respectively) when some emissions are allocated to dairy products. The wide variation in emissions reflects differences in production systems, which range from intensive feedlots with stock raised largely on grains through to rangeland and transhumance production systems. Where appropriate, a shift to diets with a higher share of plant protein, moderate intake of animal-source foods and reduced intake of saturated fats could lead to substantial decreases in GHG emissions. Benefits would also include reduced land occupation and nutrient losses to the surrounding environment, while at the same time providing health benefits and reducing mortality from diet-related non-communicable diseases. (Figure TS.19) {7.4.5, 12.4}

<div id="_idContainer061" class="Basic-Text-Frame"></div>

[[File:5cdd59f7745e0d8b1e84d32d8bfe52b7 IPCC_AR6_WGIII_Figure_TS_19.png]]

'''Figure TS.19''' '''|''' '''Regional differences in health outcome, territorial per-capita GHG emissions from national food systems, and share of food system GHG emission from energy use.''' GHG emissions are calculated according to the IPCC Tier 1 approach and are assigned to the country where they occur, not necessarily where the food is consumed. Health outcome is expressed as relative contribution of each of the following risk factors to their combined risk for deaths: Child and maternal malnutrition (red), Dietary risks (yellow) or High body-mass index (blue). {Figure 12.7}

'''Emerging food technologies such as cellular fermentation, cultured meat, plant-based alternatives to animal-based food products, and controlled environment agriculture, can bring substantial reduction in direct GHG emissions from food production (''' '''''limited evidence,''''' '''''high agreement''''' ''').''' These technologies have lower land, water, and nutrient footprints, and address concerns over animal welfare. Realising the full mitigation potential depends on access to low-carbon energy as some emerging technologies are relatively more energy intensive. This also holds for deployment of cold-chain and packaging technologies, which can help reduce food loss and waste, but increase energy and materials use in the food system. (Table TS.5) {11.4.1.3, 12.4}

<div id="TS.5.7" class="h2-container"></div>

<span id="ts.5.7-carbon-dioxide-removal-cdr"></span>
=== TS.5.7 Carbon Dioxide Removal (CDR) ===

<div id="h2-9-siblings" class="h2-siblings"></div>

'''CDR is a key element in scenarios that limit warming to 2°C''' '''(&gt;67%) or 1.5°C (&gt;50%) by 2100 (''' '''''high confidence''''' ''').''' Implementation strategies need to reflect that CDR methods differ in terms of removal process, timescale of carbon storage, technological maturity, mitigation potential, cost, co-benefits, adverse side effects, and governance requirements. (Box TS.10)

'''All the illustrative mitigation pathways (IMPs) assessed in this report use land-based biological CDR (primarily afforestation/reforestation (A/R)) and/or bioenergy with carbon capture and storage (BECCS). Some also include direct air CO''' 2 '''capture and storage (DACCS) (''' '''''high confidence''''' ''').''' Across the scenarios limiting warming to 2°C (&gt;67%) or below, cumulative volumes [[#footnote-003|30]] of BECCS reach 328 (168–763) GtCO ''2'' , CO 2 removal from AFOLU (mainly A/R) reaches 252 (20–418) GtCO ''2'' , and DACCS reaches 29 (0–339) GtCO ''2'' , for the 2020–2100 period. Annual volumes in 2050 are 2.75 (0.52–9.45) GtCO 2 yr –1 for BECCS, 2.98 (0.23–6.38) GtCO 2 yr –1 for the CO 2 removal from AFOLU (mainly A/R), and 0.02 (0–1.74) GtCO 2 yr –1 for DACCS. (Box TS.10) {12.3, Cross-Chapter Box 8 in Chapter 12}

'''Despite limited current deployment, estimated mitigation potentials for DACCS, enhanced weathering (EW) and ocean-based CDR methods (including ocean alkalinity enhancement and ocean fertilisation) are moderate to large (''' '''''medium confidence''''' ''').''' The potential for DACCS (5–40 GtCO ''2'' yr ''–1'' ) is limited mainly by requirements for low-carbon energy and by cost (100–300 (full range: 84–386) USD tCO ''2'' ''–1'' ). DACCS is currently at a medium technology readiness level. EW has the potential to remove 2–4 (full range: &lt;1 to around 100) GtCO ''2'' yr ''–1'' , at costs ranging from 50 to 200 (full range: 24–578) USD tCO ''2'' ''–1'' . Ocean-based methods have a combined potential to remove 1–100 GtCO ''2'' yr ''–1'' at costs of USD40–500 tCO ''2'' ''–1'' , but their feasibility is uncertain due to possible side effects on the marine environment. EW and ocean-based methods are currently at a low technology readiness level. {12.3}

'''CDR governance and policymaking can draw on widespread experience with emissions reduction measures (''' '''''high confidence''''' ''').''' Additionally, to accelerate research, development, and demonstration, and to incentivise CDR deployment, a political commitment to formal integration into existing climate policy frameworks is required, including reliable measurement, reporting and verification (MRV) of carbon flows. {12.3.3, 12.4, 12.5}

'''Box TS.10 | Carbon Dioxide Removal (CDR)'''

Carbon Dioxide Removal (CDR) is necessary to achieve net zero CO 2 and GHG emissions both globally and nationally, counterbalancing ‘hard-to-abate’ residual emissions. CDR is also an essential element of scenarios that limit warming to 1.5°C or below 2°C (&gt;67%) by 2100, regardless of whether global emissions reach near zero, net zero or net negative levels. While national mitigation portfolios aiming at net zero emissions or lower will need to include some level of CDR, the choice of methods and the scale and timing of their deployment will depend on the achievement of gross emission reductions, and managing multiple sustainability and feasibility constraints, including political preferences and social acceptability.

CDR refers to anthropogenic activities removing ''CO'' 2 from the atmosphere and durably storing it in ''geological'' , ''terrestrial'' , or ''ocean'' reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological, geochemical or chemical CO 2 sinks, but excludes natural CO 2 uptake not directly caused by human activities (Annex I). Carbon Capture and Storage (CCS) and Carbon Capture and Utilisation (CCU) applied to fossil CO 2 do not count as removal technologies. CCS and CCU can only be part of CDR methods if the CO 2 is biogenic or directly captured from ambient air, and stored durably in geological reservoirs or products. {12.3}

There is a great variety of CDR methods and respective implementation options {Cross-Chapter Box 8, Figure 1 in Chapter 12} . Some of these methods (like afforestation and soil carbon sequestration) have been practiced for decades to millennia, although not necessarily with the intention to remove carbon from the atmosphere. Conversely, for methods such as DACCS and BECCS, experience is growing but still limited in scale. A categorisation of CDR methods can be based on several criteria, depending on the highlighted characteristics. In this report, the categorisation is focused on the role of CDR methods in the carbon cycle, that is on the removal process ( ''land-based biological'' ; ''ocean-based biological'' ; ''geochemical'' ; ''chemical'' ) and on the time scale of storage ( ''decades to centuries'' ; ''centuries to millennia'' ; ''10,000 years or longer'' ), the latter being closely linked to different carbon storage media. Within one category (e.g., ocean-based biological CDR) options often differ with respect to other dynamic or context-specific dimensions such as mitigation potential, cost, potential for co-benefits and adverse side effects, and technology readiness level. (Table TS.7, TS.5.6, TS. 5.7) {12.3}

It is useful to distinguish between CO 2 removal from the atmosphere as the outcome of deliberate activities implementing CDR options, and the net emissions outcome achieved with the help of CDR deployment (i.e., gross emissions minus gross removals). As part of ambitious mitigation strategies at global or national levels, gross CDR can fulfil three different roles in complementing emissions abatement: (i) lowering net CO 2 or GHG emissions in the near term; (ii) counterbalancing ‘hard-to-abate’ residual emissions such as CO 2 from industrial activities and long-distance transport, or CH 4 and nitrous oxide from agriculture, in order to help reach net zero CO 2 or GHG emissions in the mid-term; (iii) achieving net negative CO 2 or GHG emissions in the long term if deployed at levels exceeding annual residual emissions {2.7, 3.3, 3.4, 3.5} . These roles of CDR are not mutually exclusive: for example, achieving net zero CO 2 or GHG emissions globally might involve individual developed countries attaining net negative CO 2 emissions at the time of global net zero, thereby allowing developing countries a smoother transition. {Cross-Chapter Box 8, Figure 2 in Chapter 12}

'''Table TS''' '''.7 |''' '''Summary of status, costs, potentials, risk and impacts, co-benefits, trade-offs and spillover effects and the role in mitigation pathways for CDR methods {12.3.2, 7.4} .''' (TRL = technology readiness level.)

{| class="wikitable"
|-
! '''CDR method'''

! '''Status (TRL)'''

! '''Cost''' 1 '''(USD tCO''' 2 –1 ''')'''

! '''Mitigation potential''' 1 '''(GtCO''' 2 '''yr''' –1 ''')'''

! '''Risk and impacts'''

! '''Co-benefits'''

! '''Trade-offs and spillover effects'''

! '''Role in mitigation pathways'''

! '''Section'''

|-
| Afforestation/reforestation

| 8–9

| 0–240

| 0.5–10

| Reversal of carbon removal through wildfire, disease, pests may occur. Reduced catchment water yield and lower groundwater level if species and biome are inappropriate.

| Enhanced employment and local livelihoods, improved biodiversity, improved renewable wood products provision, soil carbon and nutrient cycling. Possibly less pressure on primary forest.

| Inappropriate deployment at large scale can lead to competition for land with biodiversity conservation and food production.

| Substantial contribution in IAMs and also in bottom-up sectoral studies.

| {7.4}

|-
| Soil carbon sequestration in croplands and grasslands

| 8–9

| –45–100

| 0.6–9.3

| Risk of increased nitrous oxide emissions due to higher levels of organic nitrogen in the soil; risk of reversal of carbon sequestration.

| Improved soil quality, resilience and agricultural productivity.

| Attempts to increase carbon sequestration potential at the expense of production. Net addition per hectare is very small; hard to monitor.

| In development – not yet in global mitigation pathways simulated by IAMs in bottom-up studies: with medium contribution.

| {7.4}

|-
| Peatland and coastal wetland restoration

| 8–9

| Insufficient data

| 0.5–2.1

| Reversal of carbon removal in drought or future disturbance. Risk of increased CH 4 emissions.

| Enhanced employment and local livelihoods, increased productivity of fisheries, improved biodiversity, soil carbon and nutrient cycling.

| Competition for land for food production on some peatlands used for food production.

| Not in IAMs but some bottom-up studies with medium contribution.

| {7.4}

|-
| Agroforestry

| 8–9

| Insufficient data

| 0.3–9.4

| Risk that some land area lost from food production; requires very high skills.

| Enhanced employment and local livelihoods, variety of products improved soil quality, more resilient systems.

| Some trade-off with agricultural crop production, but enhanced biodiversity, and resilience of system.

| No data from IAMs, but in bottom-up sectoral studies with medium contribution.

| {7.4}

|-
| Improved forest management

| 8–9

| Insufficient data

| 0.1–2.1

| If improved management is understood as merely intensification involving increased fertiliser use and introduced species, then it could reduce biodiversity and increase eutrophication.

| In case of sustainable forest management, it leads to enhanced employment and local livelihoods, enhanced biodiversity, improved productivity.

| If it involves increased fertiliser use and introduced species it could reduce biodiversity and increase eutrophication and upstream GHG emissions.

| No data from IAMs, but in bottom-up sectoral studies with medium contribution.

| {7.4}

|-
| Biochar

| 6–7

| 10–345

| 0.3–6.6

| Particulate and GHG emissions from production; biodiversity and carbon stock loss from unsustainable biomass harvest.

| Increased crop yields and reduced non-CO 2 emissions from soil; and resilience to drought.

| Environmental impacts associated particulate matter; competition for biomass resource.

| In development – not yet in global mitigation pathways simulated by IAMs.

| {7.4}

|-
| Direct air carbon capture and storage (DACCS)

| 6

| 100–300 (84–386)

| 5–40

| Increased energy and water use.

| Water produced (solid sorbent DAC designs only).

| Potentially increased emissions from water supply and energy generation.

| In a few IAMs; DACCS complements other CDR methods.

| {12.3}

|-
| Bioenergy with carbon capture and storage (BECCS)

| 5–6

| 15–400

| 0.5–11

| Inappropriate deployment at very large scale leads to additional land and water use to grow biomass feedstock. Biodiversity and carbon stock loss if from unsustainable biomass harvest.

| Reduction of air pollutants, fuel security, optimal use of residues, additional income, health benefits, and if implemented well, it can enhance biodiversity.

| Competition for land with biodiversity conservation and food production.

| Substantial contribution in IAMs and bottom-up sectoral studies. Note – mitigation through avoided GHG emissions resulting from bioenergy use is of the same magnitude as the mitigation from CDR (TS.5.6).

| {7.4}

|-
| Enhanced weathering (EW)

| 3–4

| 50–200 (24–578)

| 2–4 (&lt;1–95)

| Mining impacts; air quality impacts of rock dust when spreading on soil.

| Enhanced plant growth, reduced erosion, enhanced soil carbon, reduced soil acidity, enhanced soil water retention.

| Potentially increased emissions from water supply and energy generation.

| In a few IAMs; EW complements other CDR methods.

| {12.3}

|-
| ‘Blue carbon management’ in coastal wetlands

| 2–3

| Insufficient data

| &lt;1

| If degraded or lost, coastal blue carbon ecosystems are expected to release most of their carbon back to the atmosphere; potential for sediment contaminants, toxicity, bioaccumulation and biomagnification in organisms; issues related to altering degradability of coastal plants; use of sub-tidal areas for tidal wetland carbon removal; effect of shoreline modifications on sediment redeposition and natural marsh accretion; abusive use of coastal blue carbon as means to reclaim land for purposes that degrade capacity for carbon removal.

| Provide many non-climatic benefits and can contribute to ecosystem-based adaptation, coastal protection, increased biodiversity, reduced upper ocean acidification; could potentially benefit human nutrition or produce fertiliser for terrestrial agriculture, anti-methanogenic feed additive, or as an industrial or materials feedstock.

| If degraded or lost, coastal blue carbon ecosystems are likely to release most of their carbon back to the atmosphere. The full delivery of the benefits at their maximum global capacity will require years to decades to be achieved.

| Not incorporated in IAMs, but in some bottom-up studies: small contribution.

| {7.4, 12.3.1}

|-
| Ocean fertilisation

| 1–2

| 50–500

| 1–3

| Nutrient redistribution, restructuring of the ecosystem, enhanced oxygen consumption and acidification in deeper waters, potential for decadal-to-millennial-scale return to the atmosphere of nearly all the extra carbon removed, risks of unintended side effects.

| Increased productivity and fisheries, reduced upper-ocean acidification.

| Sub-surface ocean acidification, deoxygenation; altered meridional supply of macro-nutrients as they are utilised in the iron-fertilised region and become unavailable for transport to, and utilisation in other regions, fundamental alteration of food webs, biodiversity.

| No data.

| {12.3.1}

|-
| Ocean alkalinity enhancement (OAE)

| 1–2

| 40–260

| 1–100

| Increased seawater pH and saturation states and may impact marine biota. Possible release of nutritive or toxic elements and compounds. Mining impacts.

| Limiting ocean acidification.

| Potentially increased emissions of CO 2 and dust from mining, transport and deployment operations.

| No data.

| {12.3.1}

|}

1 Range based on authors’ estimates (as assessed from literature) are shown, with full literature ranges shown in ( ) brackets.

<div id="TS.5.8" class="h2-container"></div>

<span id="ts.5.8-demand-side-aspects-of-mitigation"></span>

=== TS.5.8 Demand-side Aspects of Mitigation ===

<div id="h2-10-siblings" class="h2-siblings"></div>

The assessment of the social science literature and regional case studies reveals how social norms, culture, and individual choices interact with infrastructure and other structural changes over time. This provides new insight into climate change mitigation strategies, and how economic and social activity might be organised across sectors to support emission reductions. To enhance well-being, people demand services and not primary energy and physical resources per se. Focusing on demand for services and the different social and political roles people play broadens the participation in climate action. (Box TS.11)

'''Demand-side mitigation and new ways of providing services can help''' '''''Avoid''''' '''and''' '''''Shift''''' '''final service demands and''' '''''Improve''''' '''service delivery. Rapid and deep changes in demand make it easier for every sector to reduce GHG emissions in the near and mid-term (''' '''''high confidence''''' ''').''' {5.2, 5.3}

'''The indicative potential of demand-side strategies to reduce emissions of direct and indirect CO''' ''2'' '''and non-CO''' ''2'' '''GHG emissions in three end-use sectors (buildings, land transport, and food) is 40–70% globally by 2050 (''' '''''high confidence''''' ''').''' Technical mitigation potentials compared to the 2050 emissions projection of two scenarios consistent with policies announced by national governments until 2020 amount to 6.8 GtCO ''2'' for building use and construction, 4.6 GtCO ''2'' for land transport and 8.0 GtCO ''2'' -eq for food demand, and amount to 4.4 GtCO ''2'' for industry. Mitigation strategies can be classified as ''Avoid-Shift-Improve'' (ASI) options, that reflect opportunities for socio-cultural, infrastructural, and technological change. The greatest ''Avoid'' potential comes from reducing long-haul aviation and providing short-distance low-carbon urban infrastructures. The greatest ''Shift'' potential would come from switching to plant-based diets. The greatest ''Improve'' potential comes from within the building sector, and in particular increased use of energy-efficient end-use technologies and passive housing. (Figures TS.20 and TS.21) {5.3.1, 5.3.2, Figures 5.7 and 5.8, Table 5.1 and Table SM.5.2}

<div id="_idContainer070" class="Basic-Text-Frame"></div>

[[File:c9a1ea6c226c7f6fc487c9a325bc7906 IPCC_AR6_WGIII_Figure_TS_20.png]]

'''Figure TS.2''' '''0 |''' '''Demand-side strategies for mitigation.''' Demand-side mitigation is about more than behavioural change and transformation happens through societal, technological and institutional changes. {Figure 5.10, Figure 5.14}

<div id="_idContainer072" class="Basic-Text-Frame"></div>

[[File:d4a678890c5f204b33cde0642ee9f4ed IPCC_AR6_WGIII_Figure_TS_21.png]]

'''Figure T''' '''S.21 |''' '''Demand-side mitigation can be achieved through changes in socio-cultural factors, infrastructure design and use, and technology adoption.''' Mitigation response options related to demand for services have been categorised into three domains: ‘socio-cultural factors’, related to social norms, culture, and individual choices and behaviour; ‘infrastructure use’, related to the provision and use of supporting infrastructure that enables individual choices and behaviour; and ‘technology adoption’, which refers to the uptake of technologies by end users. Potentials in 2050 are estimated using the International Energy Agency’s 2020 World Energy Outlook STEPS (Stated Policy Scenarios) as a baseline. This scenario is based on a sector-by-sector assessment of specific policies in place, as well as those that have been announced by countries by mid-2020. This scenario was selected due to the detailed representation of options across sectors and sub-sectors. The heights of the coloured columns represent the potentials on which there is a high level of agreement in the literature, based on a range of case studies. The range shown by the dots connected by dotted lines represents the highest and lowest potentials reported in the literature which have low to medium levels of agreement. The demand-side potential of socio-cultural factors in the food system has two parts. The economic potential of direct emissions (mostly non-CO 2 ) demand reduction through socio-cultural factors alone is 1.9 GtCO 2 -eq without considering land-use change by diversion of agricultural land from food production to carbon sequestration. If further changes in land use enabled by this change in demand are considered, the indicative potential could reach 7 GtCO 2 -eq. The electricity panel presents separately the mitigation potential from changes in electricity demand and changes associated with enhanced electrification in end-use sectors. Electrification increases electricity demand, while it is avoided though demand-side mitigation strategies. Load management refers to demand-side flexibility that can be achieved through incentive design such as time-of-use pricing/monitoring by artificial intelligence, diversification of storage facilities, and so on. NZE (IEA Net-Zero Emissions by 2050 scenario) is used to compute the impact of end-use sector electrification, while the impact of demand-side response options is based on bottom-up assessments. Dark grey columns show the emissions that cannot be avoided through demand-side mitigation options. The table indicates which demand-side mitigation options are included. Options are categorised according to: socio-cultural factors, infrastructure use, and technology adoption. Figure SPM.7 covers potential of demand-side options for the year 2050. Figure SPM.8 covers both supply- and demand-side options and their potentials for the year 2030. {5.3, Figure 5.7, 5.SM.II}

'''Socio-cultural and lifestyle changes can accelerate climate change mitigation (''' '''''medium confidence''''' ''').''' Among 60 identified actions that could change individual consumption, individual mobility choices have the largest potential to reduce carbon footprints. Prioritising car-free mobility by walking and cycling and adoption of electric mobility could save 2 tCO ''2'' -eq cap ''–1'' yr ''–1'' . Other options with high mitigation potential include reducing air travel, cooling setpoint adjustments, reduced appliance use, shifts to public transit, and shifting consumption towards plant-based diets. {5.3.1, 5.3.1.2, Figure 5.8}

'''Box TS.11''' '''| A New Chapter in AR6 WGIII Focusing on the Social Science of Demand, and Social Aspects of Mitigation'''

The WGIII contribution to the Sixth Assessment Report of the IPCC (AR6) features a distinct chapter on demand, services and social aspects of mitigation {5} . The scope, theories, and evidence for such an assessment are addressed in Sections 5.1 and 5.4 within [https://www.ipcc.ch/chapters/chapter-5 Chapter 5] and a Social Science Primer as an Appendix to Chapter 5.

The literature on social science – from sociology, psychology, gender studies and political science for example – and climate change mitigation is growing rapidly. A bibliometric search of the literature identified 99,065 peer-reviewed academic papers, based on 34 search queries with content relevant to Chapter 5. This literature is expanding by 15% per year, with twice as many publications in the AR6 period (2014–2020) as in all previous years.

The models of stakeholders’ decisions assessed by IPCC have continuously evolved. From AR1 to AR4, rational choice was the implicit assumption: agents with perfect information and unlimited processing capacity maximising self-focused expected utility and differing only in wealth, risk attitude, and time discount rate. The AR5 introduced a broader range of goals (material, social, and psychological) and decision processes (calculation-based, affect-based, and rule-based processes). However, its perspective was still individual- and agency-focused, neglecting structural, cultural, and institutional constraints and the influence of physical and social context.

A social science perspective is important in two ways. By adding new actors and perspectives, it (i) provides more options for climate mitigation; and (ii) helps to identify and address important social and cultural barriers and opportunities to socio-economic, technological, and institutional change. Demand-side mitigation involves five sets of social actors: individuals (e.g., consumption choices, habits), groups and collectives (e.g., social movements, values), corporate actors (e.g., investments, advertising), institutions (e.g., political agency, regulations), and infrastructure actors (e.g., very long-term investments and financing). Actors either contribute to the status-quo of global high-carbon consumption, and a GDP growth-oriented economy, or help generate the desired change to a low-carbon energy-services, well-being, and equity-oriented economy. Each set of actors has novel implications for the design and implementation of both demand- and supply-side mitigation policies. They show important synergies, making energy demand mitigation a dynamic problem where the packaging and/or sequencing of different policies play a role in their effectiveness {5.5, 5.6} . Incremental interventions change social practices, simultaneously affecting emissions and well-being. The transformative change requires coordinated action across all five sets of actors (Table 5.4), using social science insights about intersection of behaviour, culture, institutional and infrastructural changes for policy design and implementation. ''Avoid'' , ''Shift'' , and ''Improve'' choices by individuals, households and communities support mitigation {5.3.1.1, Table 5.1} . They are instigated by role models, changing social norms driven by policies and social movements. They also require appropriate infrastructures designed by urban planners and building and transport professionals, corresponding investments, and a political culture supportive of demand-side mitigation action.

'''Leveraging improvements in end-use service delivery through behavioural and technological innovations, and innovations in market organisation, leads to large reductions in upstream resource use (''' '''''high confidence''''' ''').''' Analysis of indicative potentials range from a factor 10- to 20-fold improvement in the case of available energy (exergy) analysis, with the highest improvement potentials at the end-user and service-provisioning levels. Realisable service level efficiency improvements could reduce upstream energy demand by 45% in 2050. (Figure TS.20) {5.3.2, Figure 5.10}

'''''Decent living standards''''' '''(DLS) and''' '''''well-being for all''''' '''(SDG 3) are achievable if high-efficiency low-demand mitigation pathways are followed (''' '''''medium confidence''''' ''').''' Minimum requirements of energy use consistent with enabling ''well-being for all'' is between 20 and 50 GJ cap –1 yr –1 depending on the context. (Figure TS.22) {5.2.2.1, 5.2.2.2, Box 5.3}

<div id="_idContainer070a" class="Basic-Text-Frame"></div>

[[File:aaee86d540be01b2e5988c72265448f3 IPCC_AR6_WGIII_Figure_TS_22.png]]

'''Figure TS.22''' '''|''' '''Demand-side mitigation options, well-being and SDGs.''' {Figure 5.6}

'''Alternative service provision systems, for example, those enabled through digitalisation, sharing economy initiatives and circular economy initiatives, have to date made a limited contribution to climate change mitigation (''' '''''medium confidence''''' ''').''' While digitalisation through specific new products and applications holds potential for improvement in service-level efficiencies, without public policies and regulations, it also has the potential to increase consumption and energy use. Reducing the energy use of data centres, networks, and connected devices is possible in managing low-carbon digitalisation. Claims on the benefits of the circular economy for sustainability and climate change mitigation have limited evidence. (Box TS.12, Box TS.14) {5.3.4, Figures 5.12 and 5.13}

'''Box TS.12 | Circular Economy (CE)'''

In AR6, the circular economy (CE) concept {Annex I} is highlighted as an increasingly important mitigation approach that can help deliver human well-being by minimising waste of energy and resources. While definitions of CE vary, its essence is to shift away from linear ‘make and dispose’ economic models to those that emphasise product longevity, reuse, refurbishment, recycling, and material efficiency, thereby enabling more circular material systems that reduce embodied energy and emissions. {5.3.4, 8.4, 8.5, 9.5, 11.3.3}

Whereas IPCC AR4 {WGIII, Chapter 10} included a separate chapter on waste-sector emissions and waste-management practices, and AR5 {WGIII, Chapter 10} reviewed the importance of ‘reduce, reuse, recycle’ and related policies, AR6 focuses on how CE can reduce waste in materials production and consumption by optimising materials’ end-use service utility. Specific examples of CE implementations, policies, and mitigation potentials are included in Chapters 5, 8, 9, 11 and 12. {5.3, 8.4, 9.5, 11.3, 12.6}

CE is shown to empower new social actors in mitigation actions, given that it relies on the synergistic actions of producers, sellers, and consumers {11.3.3} . As an energy and resource demand-reduction strategy, it is consistent with high levels of human well-being {5.3.4.3} and ensures better environmental quality (Figure TS.22) {5.2.1} . It also creates jobs through increased sharing, reuse, refurbishment, and recycling activities. Therefore, CE contributes to several SDGs, including clean water and sanitation (SDG 6), affordable energy and clean energy (SDG 7), decent work and economic growth (SDG 8), responsible production and consumption (SDG 12) and climate action (SDG 13). {11.5.3.2}

Emissions savings derive from reduced primary material production and transport. For example, in buildings, lifetime extension, material efficiency, and reusable components reduce embodied emissions by avoiding demand for structural materials {9.3, 9.5} . At regional scales, urban/industrial symbiosis reduce primary material demand through by-product exchange networks {11.3.3} . CE strategies also exhibit enabling effects, such as material-efficient and circular vehicle designs that also improve fuel economy {10.2.2.2} . There is growing interest in ‘circular bioeconomy’ concepts applied to bio-based materials {Box 12.2} and even a ‘circular carbon economy’, wherein carbon captured via CCU {11.3.6} or CDR {3.4.6} is converted into reusable materials, which is especially relevant for the transitions of economies dependent on fossil fuel revenue. {12.6}

While there are many recycling policies, CE-oriented policies for more efficient material use with higher value retention are comparatively far fewer; these policy gaps have been attributed to institutional failures, lack of coordination, and lack of strong advocates {5.3, 9.5.3.6, Boxes 11.5 and 12.2} . Reviews of mitigation potentials reveal unevenness in the savings of CE applications and potential risks of rebound effects {5.3} . Therefore, CE policies that identify system determinants maximise potential emissions reductions, which vary by material, location, and application.

There are knowledge gaps for assessing CE opportunities within mitigation models due to CE’s many cross-sectoral linkages and data gaps related to its nascent state {3.4.4} . Opportunity exists to bridge knowledge from the industrial ecology field, which has historically studied CE, to the mitigation modelling community for improved analysis of interventions and policies for AR7. For instance, a global CE knowledge-sharing platform is helpful for CE performance measurement, reporting and accounting. {5.3, 9.5, 11.7}

'''Providing better services with less energy and resource input has high technical potential and is consistent with providing well-being for all (''' '''''medium confidence''''' ''').''' The assessment of 19 demand-side mitigation options and 18 different constituents of well-being showed that positive impacts on well-being outweigh negative ones by a factor of 11. {5.2, 5.2.3, Figure 5.6}

'''Demand-side mitigation options bring multiple interacting benefits (''' '''''high confidence''''' ''').''' Energy services to meet human needs for nutrition, shelter, health, and so on, are met in many different ways with different emissions implications that depend on local contexts, cultures, geography, available technologies, and social preferences. In the near term, many less-developed countries, and poor people everywhere, require better access to safe and low-emissions energy sources to ensure decent living standards and increase energy savings from service improvements by about 20–25%. (Figure TS.22) {5.2, 5.4.5, Figures 5.3, 5.4, 5.5 and 5.6, Boxes 5.2 and 5.3}

'''Granular technologies and decentralised energy end-use, characterised by modularity, small unit sizes and small unit costs, diffuse faster into markets and are associated with faster technological learning benefits, greater efficiency, more opportunities to escape technological lock-in, and greater employment (''' '''''high confidence''''' ''').''' Examples include solar PV systems, batteries, and thermal heat pumps. {5.3, 5.5, 5.5.3}

'''Wealthy individuals contribute disproportionately to higher emissions and have a high potential for emissions reductions while maintaining decent living standards and well-being (''' '''''high confidence''''' ''').''' Individuals with high socio-economic status are capable of reducing their GHG emissions by becoming role models of low-carbon lifestyles, investing in low-carbon businesses, and advocating for stringent climate policies. {5.4.1, 5.4.3, 5.4.4, Figure 5.14}

'''Demand-side solutions require both motivation and capacity for change (''' '''''high confidence''''' ''').''' Motivation by individuals or households worldwide to change energy consumption behaviour is generally low. Individual behavioural change is insufficient for climate change mitigation unless embedded in structural and cultural change. Different factors influence individual motivation and capacity for change in different demographics and geographies. These factors go beyond traditional socio-demographic and economic predictors and include psychological variables such as awareness, perceived risk, subjective and social norms, values, and perceived behavioural control. Behavioural nudges promote easy behaviour change, for example, ‘ ''Improve'' ’ actions such as making investments in energy efficiency, but fail to motivate harder lifestyle changes ( ''high confidence'' ). {5.4}

'''Behavioural interventions, including the way choices are presented to end users (an intervention practice known as choice architecture), work synergistically with price signals, making the combination more effective (''' '''''medium confidence''''' ''').''' Behavioural interventions through nudges, and alternative ways of redesigning and motivating decisions, alone provide small to medium contributions to reduce energy consumption and GHG emissions. Green defaults, such as automatic enrolment in ‘green energy’ provision, are highly effective. Judicious labelling, framing, and communication of social norms can also increase the effect of mandates, subsidies, or taxes. {5.4, 5.4.1, Table 5.3, 5.3}

'''Cultural change, in combination with new or adapted infrastructure, is necessary to enable and realise many''' '''''Avoid''''' '''and''' '''''Shift''''' '''options (''' '''''medium confidence''''' ''').''' By drawing support from diverse actors, narratives of change can enable coalitions to form, providing the basis for social movements to campaign in favour of (or against) societal transformations. People act and contribute to climate change mitigation in their diverse capacities as consumers, citizens, professionals, role models, investors, and policymakers. {5.4, 5.5, 5.6}

'''Collective action as part of social or lifestyle movements underpins system change (''' '''''high confidence''''' ''').''' Collective action and social organising are crucial to shift the possibility space of public policy on climate change mitigation. For example, climate strikes have given voice to youth in more than 180 countries. In other instances, mitigation policies allow the active participation of all stakeholders, resulting in building social trust, new coalitions, legitimising change, and thus initiate a positive cycle in climate governance capacity and policies. {5.4.2, Figure 5.14}

'''Transition pathways and changes in social norms often start with pilot experiments led by dedicated individuals and niche groups (''' '''''high confidence''''' ''').''' Collectively, such initiatives can find entry points to prompt policy, infrastructure, and policy reconfigurations, supporting the further uptake of technological and lifestyle innovations. Individuals’ agency is central as social change agents and narrators of meaning. These bottom-up socio-cultural forces catalyse a supportive policy environment, which enables changes. {5.5.2}

'''The current effects of climate change, as well as some mitigation strategies, are threatening the viability of existing business practices, while some corporate efforts also delay mitigation action (''' '''''medium confidence''''' ''').''' Policy packages that include job creation programmes can help to preserve social trust, livelihoods, respect, and dignity of all workers and employees involved. Business models that protect rent-extracting behaviour may sometimes delay political action. Corporate advertisement and brand-building strategies may also attempt to deflect corporate responsibility to individuals or aim to appropriate climate-care sentiments in their own brand–building. {5.4.3, 5.6.4}

'''Middle actors – professionals, experts, and regulators – play a crucial, albeit underestimated and underutilised, role in establishing low-carbon standards and practices (''' '''''medium confidence''''' ''').''' Building managers, landlords, energy-efficiency advisers, technology installers, and car dealers influence patterns of mobility and energy consumption by acting as middle actors or intermediaries in the provision of building or mobility services and need greater capacity and motivation to play this role. (Figure TS.20a) {5.4.3}

'''Social influencers and thought leaders can increase the adoption of low-carbon technologies, behaviours, and lifestyles (''' '''''high confidence''''' ''').''' Preferences are malleable and can align with a cultural shift. The modelling of such shifts by salient and respected community members can help bring about changes in different service provisioning systems. Between 10% and 30% of committed individuals are required to set new social norms. {5.2.1, 5.4}

<div id="TS.5.9" class="h2-container"></div>

<span id="ts.5.9-mitigation-potential-across-sectors-and-systems"></span>
=== TS.5.9 Mitigation Potential Across Sectors and Systems ===

<div id="h2-11-siblings" class="h2-siblings"></div>

'''The total emission mitigation potential achievable by the year 2030, calculated based on sectoral assessments, is sufficient to reduce global greenhouse gas (GHG) emissions to half of the current (2019) level or less (''' '''''high confidence''''' ''').''' This potential – 31–44 GtCO 2 -eq – requires the implementation of a wide range of mitigation options. Options with mitigation costs lower than USD20 tCO 2 –1 make up more than half of this potential and are available for all sectors. The market benefits of some options exceed their costs. (Figure TS.23) {12.2, Table 12.3}

<div id="_idContainer097" class="Basic-Text-Frame"></div>

[[File:8ba0f337251aca39bc2e17085c893d19 IPCC_AR6_WGIII_Figure_TS_23.png]]

'''Figure TS.2''' '''3 |''' '''Overview of emission mitigation options and their cost and potential for the year 2030.''' The mitigation potential of each option is the quantity of net greenhouse gas emission reductions that can be achieved by a given mitigation option relative to specified emission baselines that reflects what would be considered current policies in the period 2015–2019. Mitigation options may overlap or interact and cannot simply be summed together. The potential for each option is broken down into cost categories (see legend). Only monetary costs and revenues are considered. If costs are less than zero, lifetime monetary revenues are higher than lifetime monetary costs. For wind energy, for example, negative cost indicates that the cost is lower than that of fossil-based electricity production. The error bars refer to the total potential for each option. The breakdown into cost categories is subject to uncertainty. Where a smooth colour transition is shown, the breakdown of the potential into cost categories is not well researched, and the colours indicate only into which cost category the potential can predominantly be found in the literature. {Figure SPM.8, 6.4, Table 7.3, Supplementary Material Table 9.SM.2, Supplementary Material Table 9.SM.3, 10.6, 11.4, Figure 11.13, 12.2, Supplementary Material 12.SM.1.2.3}

'''Cross-sectoral considerations in mitigation finance are critical for the effectiveness of mitigation action as well as for balancing the often conflicting social, developmental, and environmental policy goals at the sectoral level (''' '''''medium confidence''''' ''').''' True resource mobilisation plans that properly address mitigation costs and benefits at sectoral level cannot be developed in isolation of their cross-sectoral implications. There is an urgent need for multilateral financing institutions to align their frameworks and delivery mechanisms, including the use of blended financing to facilitate cross-sectoral solutions as opposed to causing competition for resources among sectors ''.'' {12.6.4}

'''Carbon leakage is a cross-sectoral and cross-country consequence of differentiated climate policy (''' '''''robust evidence, medium agreement''''' ''').''' Carbon leakage occurs when mitigation measures implemented in one country/sector leads to increased emissions in other countries/sectors. Global commodity value chains and associated international transport are important mechanisms through which carbon leakage occurs. Reducing emissions from the value chain and transportation can offer opportunities to mitigate three elements of cross-sectoral spillovers and related leakage: (i) domestic cross-sectoral spillovers within the same country; (ii) international spillovers within a single sector resulting from substitution of domestic production of carbon-intensive goods with their imports from abroad; and (iii) international cross-sectoral spillovers among sectors in different countries ''.'' {12.6.3}

<div id="TS.6" class="h1-container"></div>

<span id="ts.6-implementation-and-enabling-conditions"></span>