Editing IPCC:AR6/WGIII/Chapter-4 (section)

=== Box 4.3 | Examples of High-renewable Accelerated Mitigation Pathways ===

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Many accelerated mitigation pathways include high shares of renewable energy, with national variations. In Europe, some argue that the EU 2050 net zero GHG emissions goal can be met with 100% renewable power generation, including use of renewable electricity to produce hydrogen, biofuels (including imports), and synthetic hydrocarbons, but will require significant increases in transmission capacity ( [[#Duscha--2019|Duscha et al. 2019]] ; [[#Zappa--2019|Zappa et al. 2019]] ). [[#Capros--2019|Capros et al. (2019)]] explore a 1.5°C compatible pathway that includes 85% renewable generation, with battery, pumped hydro, and chemical storage for variable renewables. High-renewable scenarios also exist for individual Member States. In France, for example, [[#Krakowski--2016|Krakowski et al. (2016)]] propose a 100% renewable power generation scenario that relies primarily on wind (62%), solar PV (26%) and oceans (12%). To reach this aim, integration into the European grid is of vital importance ( [[#Brown--2018|Brown et al. 2018]] ). While debated, incremental costs could be limited regardless of specific assumptions of future costs of individual technologies ( [[#Shirizadeh--2020|Shirizadeh et al. 2020]] ). In Germany, similarly, 100% renewable electricity systems are found feasible by numerous studies ( [[#Oei--2020|Oei et al. 2020]] ; [[#Thomas%20Klaus--2010|Thomas Klaus et al. 2010]] ; Wuppertal-Institut 2021; [[#Hansen--2019|Hansen et al. 2019]] ).

In South Africa, it is found that long-term mitigation goals could be achieved with accelerated adoption of solar PV and wind generation, if the electricity sector decarbonises by phasing-out coal entirely by 2050, even if CCS is not feasible before 2025 (Altieri et al. 2015; Beck et al. 2013). Abundant solar PV and wind potential, coupled with land availability suggest that more than 75% of power generation could ultimately originate from solar PV and wind ( [[#Oyewo--2019|Oyewo et al. 2019]] ; [[#Wright--2019|Wright et al. 2019]] ).

For the US, share of renewables in power generation in 2050 in accelerated mitigation scenarios vary widely, 40% in ( [[#Hodson--2018|Hodson et al. 2018]] ; [[#Jayadev--2020|Jayadev et al. 2020]] ), more than half renewable and nuclear in ( [[#Victor--2018|Victor et al. 2018]] ) to 100% in Jacobson et al. (2017, 2019).

Box 4.3

Under cost optimisation scenarios for Brazil, electricity generation, which is currently dominated by hydropower, could reach 100% by adding biomass ( [[#Köberle--2020|Köberle et al. 2020]] ). Other studies find that renewable energy, including biomass, could account for more than 30% of total electricity generation ( [[#Nogueira%20de%20Oliveira--2016|Nogueira de Oliveira et al. 2016]] ; Portugal- [[#Pereira--2016|Pereira et al. 2016]] ).

In Colombia, where hydropower resources are abundant and potential also exist for solar and wind, a deep decarbonisation pathway would require 57% renewable power generation by 2050 (Arango-Aramburo et al. 2019) while others find 80% would be possible ( [[#Delgado--2020|Delgado et al. 2020]] ).

In Asia, Japan could have up to 50% variable renewable electricity supply to reduce CO 2 emissions by 80% by 2050 in some of its deep mitigation scenarios ( [[#Kato--2019|Kato and Kurosawa 2019]] ; [[#Sugiyama--2019|Sugiyama et al. 2019]] ; [[#Ju--2021|Ju et al. 2021]] ; [[#Shiraki--2021|Shiraki et al. 2021]] ; [[#Silva%20Herran--2021|Silva Herran and Fujimori 2021]] ). One view of China’s 1.5°C pathway includes 59% renewable power generation by 2050 ( [[#Jiang--2018|Jiang et al. 2018]] ). One view of India’s 1.5°C pathway also includes 52% renewable power generation, and would require storage needs for 35% of generation ( [[#Parikh--2018|Parikh et al. 2018]] ).

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<span id="bioenergy-plays-significant-role-in-resource-abundant-countries-in-latin-america-and-parts-of-europe"></span>
==== 4.2.5.3 Bioenergy Plays Significant Role in Resource Abundant Countries in Latin America and Parts of Europe ====

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Bioenergy could account for up to 40% of Brazil’s total final energy consumption, and a 60% share of fuel for light-duty vehicles by 2030 ( [[#Lefèvre--2018|Lefèvre et al. 2018]] ), and is considered most cost-effective in transport and industrial applications ( [[#Lap--2020|Lap et al. 2020]] ). BECCS in the power sector is also considered cost-effective option for supply-side mitigation ( [[#Borba--2012|Borba et al. 2012]] ; [[#Herreras%20Martínez--2015|Herreras Martínez et al. 2015]] ; [[#Lucena--2016|Lucena et al. 2016]] ).

Bioenergy also plays a prominent role in some EU countries’ deep decarbonisation strategies. Domestic biomass alone can help Germany meet its 95% CO 2 reduction by 2050 goal, and biomass and CCS together are needed to reduce CO 2 by 80% by 2050 in the Netherlands ( [[#Mikova--2019|Mikova et al. 2019]] ). Studies suggest that mitigation efforts in France include biofuels and significant increases in biomass use, including up to 45% of industry energy by 2050 for its net GHG neutrality goal ( [[#Doumax-Tagliavini--2018|Doumax-Tagliavini and Sarasa 2018]] ; [[#Capros--2019|Capros et al. 2019]] ). Increased imports may be needed to meet significant increases in EU’s bioenergy use, which could affect energy security and the sustainability of bioenergy production outside of the EU ( [[#Mandley--2020|Mandley et al. 2020]] ; [[#Daioglou--2020|Daioglou et al. 2020]] ).

While BECCS is needed in multiple accelerated mitigation pathways, large-scale land-based biological CDR may not prove as effective as expected, and its large-scale deployment may result in ecological and social impacts, suggesting it may not be a viable carbon removal strategy in the next 10–20 years ( [[#Vaughan--2016|Vaughan and Gough 2016]] ; [[#Boysen--2017|Boysen et al. 2017]] ; [[#Dooley--2018|Dooley and Kartha 2018]] ). The effectiveness of BECCS could depend on local contexts, choice of biomass, fate of initial aboveground biomass and fossil-fuel emissions offsets – carbon removed through BECCS could be offset by losses due to land-use change ( [[#Harper--2018|Harper et al. 2018]] ; [[#Butnar--2020|Butnar et al. 2020]] ; [[#Calvin--2021|Calvin et al. 2021]] ). Large-scale BECCS may push planetary boundaries for freshwater use, exacerbate land-system change, significantly alter biosphere integrity and biogeochemical flows ( [[#Heck--2018|Heck et al. 2018]] ; [[#Fuhrman--2020|Fuhrman et al. 2020]] ; [[#Stenzel--2021|Stenzel et al. 2021]] ; Ai et al. 2021). (Sections 7.4 and 12.5)

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<span id="ccs-may-be-needed-to-mitigate-emissions-from-the-remaining-fossil-fuels-that-cannot-be-decarbonised-but-the-economic-feasibility-of-deployment-is-not-yet-clear"></span>
==== 4.2.5.4 CCS May Be Needed to Mitigate Emissions From the Remaining Fossil Fuels That Cannot Be Decarbonised, but the Economic Feasibility of Deployment Is Not Yet Clear ====

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CCS is present in many accelerated mitigation scenarios in the literature. In Brazil, ( [[#Nogueira%20de%20Oliveira--2016|Nogueira de Oliveira et al. 2016]] ) consider BECCS and CCS in hydrogen generation more feasible than CCS in thermal power plants, with costs ranging from USD70–100 per tCO 2 . Overall, ( [[#van%20der%20Zwaan--2016|van der Zwaan et al. 2016]] ) estimate that 33–50% of total electricity generation in Latin America could be ultimately covered by CCS. In Japan, CCS and increased bioenergy adoption plus waste-to-energy and hydrogen-reforming from fossil fuel are all considered necessary in the power sector in existing studies, with potential up to 200 MtCO 2 yr –1 (Ashina et al. 2012; [[#Oshiro--2017a|Oshiro et al. 2017a]] ; [[#Kato--2019|Kato and Kurosawa 2019]] ; [[#Sugiyama--2021|Sugiyama et al. 2021]] ). In parts of the EU, after 2030, CCS could become profitable with rising CO 2 prices ( [[#Schiffer--2015|Schiffer 2015]] ). CDR is seen as necessary in some net GHG neutrality pathways ( [[#Capros--2019|Capros et al. 2019]] ) but evidence on cost-effectiveness is scarce and uncertain ( [[#European%20Commission--2013|European Commission 2013]] ). For France and Sweden, ( [[#Millot--2020|Millot et al. 2020]] ) include CCS and BECCS to meet net zero GHG emissions by 2050. For Italy, ( [[#Massetti--2012|Massetti 2012]] ) propose a zero-emission electricity scenario with a combination of renewable and coal, natural gas, and BECCS.

In China, an analysis concluded that CCS is necessary for remaining coal and natural gas generation out to 2050 ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#Energy%20Transitions%20Commission%20and%20Rocky%20Mountain%20Institute--2019|Energy Transitions Commission and Rocky Mountain Institute 2019]] ). Seven to 10 CCS projects with installed capacity of 15 GW by 2020 and total CCS investment of 105 billion RMB (2010 RMB) are projected to be needed by 2050 under a 2°C compatible pathway according to ( [[#Jiang--2013|Jiang et al. 2013]] , 2016; [[#Lee--2018|Lee et al. 2018]] ). Under 1.5°C pathway, an analysis found China would need full CCS coverage of the remaining 12% of power generation from coal and gas power and 250 GW of BECCS ( [[#Jiang--2018|Jiang et al. 2018]] ). Combined with expanded renewable and nuclear development, total estimated investment in this study is 5% of China’s total GDP in 2020, 1.3% in 2030, and 0.6% in 2050 ( [[#Jiang--2016|Jiang et al. 2016]] ).

Views regarding feasibility of CCS can vary greatly for the same country. In the case of India’s electricity sector for instance, some studies indicate that CCS would be necessary ( [[#Vishwanathan--2018a|Vishwanathan et al. 2018a]] ), while others do not – citing concerns around its feasibility due to limited potential sites and issues related to socio-political acceptance – and rather point to very ambitious increase in renewable energy, which in turn could pose significant challenges in systematically integrating renewable energy into the current energy systems ( [[#Viebahn--2014|Viebahn et al. 2014]] ; [[#Mathur--2020|Mathur and Shekhar 2020]] ). Some limitations of CCS, including uncertain costs, lifecycle and net emissions, other biophysical resource needs, and social acceptance are acknowledged in existing studies ( [[#Viebahn--2014|Viebahn et al. 2014]] ; [[#Jacobson--2019|Jacobson 2019]] ; [[#Mathur--2020|Mathur and Shekhar 2020]] ; [[#Sekera--2020|Sekera and Lichtenberger 2020]] ).

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 ambition for gross emission reductions, how sustainability and feasibility constraints are managed, and how political preferences and social acceptability evolve (Cross-Chapter Box 8). Furthermore, mitigation deterrence may create further uncertainty, as anticipated future CDR could dilute incentives to reduce emissions now ( [[#Grant--2021|Grant et al. 2021]] ), and the political economy of net negative emissions has implications for equity ( [[#Mohan--2021|Mohan et al. 2021]] ).

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<span id="nuclear-power-is-considered-strategic-for-some-countries-while-others-plan-to-reach-their-mitigation-targets-without-additional-nuclear-power"></span>
==== 4.2.5.5 Nuclear Power Is Considered Strategic for Some Countries, While Others Plan to Reach Their Mitigation Targets Without Additional Nuclear Power ====

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Nuclear power generation is developed in many countries, though larger-scale national nuclear generation does not tend to associate with significantly lower carbon emissions ( [[#Sovacool--2020|Sovacool et al. 2020]] ). Unlike other energy sources such as wind and PV solar, levelised costs of nuclear power has been rising in the last decades ( [[#Grubler--2010|Grubler 2010]] ; [[#Gilbert--2017|Gilbert et al. 2017]] ; [[#Portugal-Pereira--2018|Portugal-Pereira et al. 2018]] ). This is mainly due to overrun of overnight construction costs related to delays in project approvals and construction, and more stringent passive safety measures, which increases the complexity of systems. After the Fukushima Daiichi accident in Japan, nuclear programs in several countries have been phased out or cancelled ( [[#Carrara--2020|Carrara 2020]] ; [[#Huenteler--2012|Huenteler et al. 2012]] ; [[#Kharecha--2019|Kharecha and Sato 2019]] ; [[#Hoffman--2018|Hoffman and Durlak 2018]] ). Also the compatibility of conventional prresurised water reactors and boiling water reactors with large proportion of renewable energy in the grid it is yet to be fully understood.

Accelerated mitigation scenarios offer contrasting views on the share of nuclear in power generation. In the USA, ( [[#Victor--2018|Victor et al. 2018]] ) build a scenario in which nuclear contributes 23% of CO 2 emission reductions needed to reduce GHG emissions by 80% from 2005 levels by 2050. Deep power sector decarbonisation pathways could require a two-folded increase in nuclear capacity according to ( [[#Jayadev--2020|Jayadev et al. 2020]] ) for the USA, and nearly a ten-fold increase for Canada, but may be difficult to implement ( [[#Vaillancourt--2017|Vaillancourt et al. 2017]] ). For China to meet a 1.5°C pathway or achieve carbon neutrality by 2050, nuclear may represent 14–28% of power generation in 2050 according to ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#China%20National%20Renewable%20Energy%20Centre--2019|China National Renewable Energy Centre 2019]] ; [[#Energy%20Transitions%20Commission%20and%20Rocky%20Mountain%20Institute--2019|Energy Transitions Commission and Rocky Mountain Institute 2019]] ). For South Korea, [[#Hong--2014|Hong et al. (2014)]] and [[#Hong--2018|Hong and Brook (2018)]] find that increasing nuclear power can help complement renewables in decarbonising the grid. Similarly, India has put in place a three-stage nuclear programme which aims to enhance nuclear power capacity from the current level of 6 GW to 63 GW by 2032, if fuel supply is ensured (GoI 2015). Nuclear energy is also considered necessary as part of accelerated mitigation pathways in Brazil, although it is not expected to increase significantly by 2050 even under stringent low-carbon scenarios ( [[#Lucena--2016|Lucena et al. 2016]] ). France developed its nuclear strategy in response to energy security concerns after the 1970s oil crisis, but has committed to reducing nuclear’s share of power generation to 50% by 2035 ( [[#Millot--2020|Millot et al. 2020]] ). Conversely, some analysis find deep mitigation pathways, including net zero GHG emissions and 80–90% reduction from 2013 levels, feasible without additional nuclear power in EU-28 and Japan respectively, but assuming a combination of bio- and novel fuels and CCS or land-use based carbon sinks ( [[#Kato--2019|Kato and Kurosawa 2019]] ; [[#Duscha--2019|Duscha et al. 2019]] ).

Radically more efficient use of energy than today, including electricity, is a complementary set of measures, explored in the following.

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<span id="efficient-cooling-slcfs-and-co-benefits"></span>
==== 4.2.5.6 Efficient Cooling, SLCFs and Co-benefits ====

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In warmer climate regions undergoing economic transitions, improving the energy efficiency of cooling and refrigeration equipment is often important for managing peak electricity demand and can have co-benefits for climate mitigation as well as SLCF reduction, as expected in India, Africa, and Southeast Asia in the future.

Air conditioner adoption is rising significantly in low- and middle-income countries as incomes rise and average temperatures increase, including in Southeast Asian countries such as Thailand, Indonesia, Vietnam, and the Philippines, as well as Brazil, Pakistan, Bangladesh, and Nigeria ( [[#Biardeau--2020|Biardeau et al. 2020]] ). Cooling appliances are expected to increase from 3.6 billion to 9.5 billion by 2050, though up to 14 billion could be required to provide adequate cooling for all ( [[#Birmingham%20Energy%20Institute--2018|Birmingham Energy Institute 2018]] ). Current technology pathways are not sufficient to deliver universal access to cooling or meet the 2030 targets under the SDGs, but energy efficiency, including in equipment efficiency like air conditioners, can reduce this demand and help limit additional emissions that would further exacerbate climate change ( [[#Biardeau--2020|Biardeau et al. 2020]] ; [[#Dreyfus--2020|Dreyfus et al. 2020]] ; UNEP and [[#IEA--2020|IEA 2020]] ). Some countries (India, South Africa) have started to recognise the need for more efficient equipment in their mitigation strategies (Altieri et al. 2016; [[#Ouedraogo--2017|Ouedraogo 2017]] ; [[#Paladugula--2018|Paladugula et al. 2018]] ).

One possible synergy between SLCF and climate change mitigation is the simultaneous improvement in energy efficiency in refrigeration and air-conditioning equipment during the hydrofluorocarbon (HFC) phase-down, as recognised in the Kigali Amendment to the Montreal Protocol. The Kigali Amendment and related national and regional regulations are projected to reduce future radiative forcing from HFCs by about half in 2050 compared to a scenario without any HFC controls, and to reduce future global average warming in 2100 from a baseline of 0.3°C–0.5°C to less than 0.1°C, according to a recent scientific assessment of a wide literature ( [[#World%20Meteorological%20Organization--2018|World Meteorological Organization 2018]] ). If ratified by signatories, the rapid phase-down of HFCs under the Kigali Amendment is possible because of extensive replacement of high-global warming potential (GWP) HFCs with commercially available low-GWP alternatives in refrigeration and air-conditioning equipment. Each country’s choices of alternative refrigerants will likely be determined by energy efficiency, costs, and refrigerant toxicity and flammability. National and regional regulations will be needed to drive technological innovation and development ( [[#Polonara--2017|Polonara et al. 2017]] ).

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<span id="efficient-buildings-cooler-in-summer-warmer-in-winter-towards-net-zero-energy"></span>
==== 4.2.5.7 Efficient Buildings, Cooler in Summer, Warmer in Winter, Towards Net Zero Energy ====

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Most accelerated mitigation pathway scenarios include significant increase in building energy efficiency. Countries in cold regions, in particular, often focus more on building sector GHG emissions mitigation measures such as improving building envelopes and home appliances, and electrifying space heating and water heating.

For example, scenarios for Japan project continued electrification of residential and commercial buildings to 65% and 79% respectively by 2050 to reach 70–90% CO 2 reduction from 2013 levels ( [[#Kato--2019|Kato and Kurosawa 2019]] ). Similarly, a mitigation pathway for China compatible with 1.5°C would require 58% to 70% electrification of buildings according to ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#China%20National%20Renewable%20Energy%20Centre--2019|China National Renewable Energy Centre 2019]] E; nergy Transitions Commission and Rocky Mountain Institute 2019). For the EU-28 to reach net carbon neutrality, complete substitution of fossil fuels with electricity (up to 65% share), district heating, and direct use of solar and ambient heat are projected to be needed for buildings, along with increased use of solar thermal and heat pumps for heating ( [[#Duscha--2019|Duscha et al. 2019]] ). In the UK and Canada, improved insulation to reduce energy demand and efficient building appliances and heating systems are important building strategies needed to reduce emissions to zero by 2050 ( [[#Vaillancourt--2017|Vaillancourt et al. 2017]] ; [[#Chilvers--2017|Chilvers et al. 2017]] ; [[#Roberts--2018a|Roberts et al. 2018a]] ). In Ireland, achieving 80–95% emissions reduction below 1990 levels by 2050 also requires changes in building energy technology and efficiency, including improving building envelopes, fuel switching for residential buildings, and replacing service-sector coal use with gas and renewables according to ( [[#Chiodi--2013|Chiodi et al. 2013]] ). In South Africa, improving industry and building energy efficiency is also considered a key part of mitigation strategies (Altieri et al. 2016; [[#Ouedraogo--2017|Ouedraogo 2017]] ).

In addition, an increasing number of countries have set up net zero energy building targets (Table 4.8) ( [[#Höhne--2020|Höhne et al. 2020]] ). Twenty-seven countries have developed roadmap documents for NZEBs, mostly in developed countries in Europe, North America, and Asia-Pacific, focusing on energy efficiency and improved insulation and design, renewable and smart technologies ( [[#Mata--2020|Mata et al. 2020]] ). The EU, Japan and the USA (the latter for public buildings only) have set targets for shifting new buildings to 100% near-zero energy buildings by 2030, with earlier targets for public buildings. Scotland has a similar target for 2050 ( [[#Höhne--2020|Höhne et al. 2020]] ). Technologies identified as needed for achieving near-zero energy buildings vary by region, but include energy-efficient envelope components, natural ventilation, passive cooling and heating, high performance building systems, air heat recovery, smart and information and communication technologies, and changing future heating and cooling supply fuel mixes towards solar, geothermal, and biomass ( [[#Mata--2020|Mata et al. 2020]] ). Sub-national regions in Spain, USA, Germany, and Mexico have set local commitments to achieving net zero carbon new buildings by 2050, with California having the most ambitious aspirational target of zero net energy buildings for all new buildings by 2030 ( [[#Höhne--2020|Höhne et al. 2020]] ). The EU is also targeting the retrofitting of 3% of existing public buildings to zero-energy, with emphasis on greater thermal insulation of building envelopes ( [[#Höhne--2020|Höhne et al. 2020]] ; [[#Mata--2020|Mata et al. 2020]] ). China’s roadmaps have emphasised insulation of building envelope, heat recovery systems in combination with renewable energy, including solar, shallow geothermal, and air source heat pumps ( [[#Mata--2020|Mata et al. 2020]] ).

'''Table 4.8 | Targets by countries, regions, cities and businesses on decarbonising the b''' '''uilding sector.'''

{| class="wikitable"
|-
!
! Countries

! Sub-national Regions

! Cities

! Businesses

|-
| Shift to 100% (near-)zero energy buildings for new buildings

| 3

| 6

| &gt;28

| &gt;44

|-
| Fully decarbonise the building sector

| 1

| 6

| &gt;28

| &gt;44

|-
| Phase out fossil fuels (for example, gas) for residential heating

| 1

| –

| &gt;3

|
|-
| Increase the rate of zero-energy renovations

| 1 (public buildings)

|
|}

Source: [[#Höhne--2020|Höhne et al. (2020)]] , supplementary information. [https://newclimate.org/ambitiousactions https://newclimate.org/am bitiousactions] .

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<span id="electrifying-transport"></span>
==== 4.2.5.8 Electrifying Transport ====

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Electrification of transport in tandem with power sector decarbonisation is expected to be a key strategy for deep CO 2 mitigation in many countries. Passenger transport and light duty freight can already be electrified, but electrifying heavy-duty road transport and fuel switching in aviation and shipping are much more difficult and have not been addressed in most of the recent research.

In Germany, widespread electrification of private vehicles is expected by 2030 ( [[#Schmid--2012|Schmid and Knopf 2012]] ) while for the EU-28, 50% overall transport electrification (excluding feedstock) and 75% electrification of road transport is needed to reach net carbon neutrality according to ( [[#Duscha--2019|Duscha et al. 2019]] ). In addition, novel fuels such as hydrogen, synthetic hydrocarbons and sustainable biogenic fuels are needed to decarbonise aviation and water transport to achieve net carbon neutrality ( [[#Duscha--2019|Duscha et al. 2019]] ).

In India, electrification, hydrogen, and biofuels are key to decarbonising the transport sector ( [[#Dhar--2018|Dhar et al. 2018]] ; [[#Mittal--2018|Mittal et al. 2018]] ; [[#Vishwanathan--2018b|Vishwanathan et al. 2018b]] ; [[#Mathur--2020|Mathur and Shekhar 2020]] ). Under a 1.5°C scenario, nearly half of the light-duty passenger vehicle stock needs to be electrified according to ( [[#Parikh--2018|Parikh et al. 2018]] ). In China, a 1.5°C-compatible pathway would require electrification of two-fifths of transport ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#China%20National%20Renewable%20Energy%20Centre--2019|China National Renewable Energy Centre 2019]] ).

Similarly, in Canada, electrification of 59% of light-duty trucks and 23% of heavy-duty trucks are needed as part of overall strategy to reduce CO 2 emissions by 80% by 2050. In addition, hydrogen is expected to play a major role by accounting for nearly one-third of light-duty trucks, 68% of heavy-duty trucks, and 33% of rail by 2050 according to [[#Hammond--2020|Hammond et al. (2020)]] .

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<span id="urban-form-meets-information-technology"></span>
==== 4.2.5.9 Urban Form Meets Information Technology ====

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Beyond technological measures, some densely populated countries including Germany, Japan, and India are exploring using information technology/internet of things (IOT) to support mode-shifting and reduce mobility demand through broader behaviour and lifestyle changes (Ashina et al. 2012; [[#Canzler--2016|Canzler and Wittowsky 2016]] ; Aggarwal 2017; [[#Dhar--2018|Dhar et al. 2018]] ; [[#Vishwanathan--2018b|Vishwanathan et al. 2018b]] ). In Japan, accelerated mitigation pathways consider the use of information technology and internet of things (IoT) to transform human behaviour and transition to a sharing economy (Ashina et al. 2012; [[#Oshiro--2017a|Oshiro et al. 2017a]] , 2018). In Germany, one study points to including electromobility information and communication technologies in the transport sector as key ( [[#Canzler--2016|Canzler and Wittowsky 2016]] ) while another emphasise shifting from road to rail transport, and reduced distances travelled as other possible transport strategies ( [[#Schmid--2012|Schmid and Knopf 2012]] ). India’s transport sector strategies also include use of information technology and the internet, a transition to a sharing economy, and increasing infrastructure investment ( [[#Dhar--2018|Dhar et al. 2018]] ; [[#Vishwanathan--2018b|Vishwanathan et al. 2018b]] ). Behaviour and lifestyle change along with stakeholder integration in decision-making are considered key to implementing new transport policies (Aggarwal 2017; [[#Dhar--2018|Dhar et al. 2018]] ).

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==== 4.2.5.10 Industrial Energy Efficiency ====

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Industrial energy efficiency improvements are considered in nearly all countries but for countries where industry is expected to continue to be a key sector, new and emerging technologies that require significant R&amp;D investment, such as hydrogen and CCS, make ambitious targets achievable.

In China, for example, non-conventional electrical and renewable technologies, including low-grade renewable heat, biomass use for high-temperature heat in steel and cement sectors, and additional electrification in glass, food and beverage, and paper and pulp industries, are part of scenarios that achieve 60% reduction in national CO 2 emission by 2050 ( [[#Khanna--2019|Khanna et al. 2019]] ; [[#Zhou--2019|Zhou et al. 2019]] ), in addition to increased recycled steel for electric arc furnaces and direct electrolysis or hydrogen-based direct reduction of iron and CCS utilisation in clinker and steel-making ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#China%20National%20Renewable%20Energy%20Centre--2019|China National Renewable Energy Centre 2019]] ). Similarly, in India, ( [[#Vishwanathan--2020|Vishwanathan and Garg 2020]] ) point to the need for renewable energy and CCS to decarbonise the industrial sector. In EU-28, net CO 2 neutrality can only be reached with 92% reduction in industrial emissions relative to 1990, through electrification, efficiency improvement and new technologies such as hydrogen-based direct reduction of steel, low-carbon cement and recycling ( [[#Duscha--2019|Duscha et al. 2019]] ). Both China and EU see 50% of industry electrification by 2050 as needed to meet 1.5°C and net carbon neutrality pathways ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#Capros--2019|Capros et al. 2019]] ).

Aggressive adoption of technology solutions for power sector decarbonisation coupled with end-use efficiency improvements and low-carbon electrification of buildings, industry and transport provides a pathway for accelerated mitigation in many key countries, but will still be insufficient to meet zero emission/1.5°C goals for all countries. Although not included in a majority of the studies related to pathways and national modelling analysis, energy demand reduction through deeper efficiency and other measures such as lifestyle changes and system solutions that go beyond components, as well as the co-benefits of the reduction of short-lived pollutants, needs to be evaluated for inclusion in future zero emission/1.5°C pathways.

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<span id="lowering-demand-downscaling-economies"></span>
==== 4.2.5.11 Lowering Demand, Downscaling Economies ====

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Studies have identified socio-technological pathways to help achieve net zero CO 2 and GHG targets at national scale, that in aggregate are crucial to keeping global temperature below agreed limits. However, most of the literature focuses on supply-side options, including carbon dioxide removal mechanisms (BECCS, afforestation, and others) that are not fully commercialised (Cross-Chapter Box 8 in Chapter 12). Costs to research, deploy, and scale up these technologies are often high. Recent studies have addressed lowering demand through energy conversion efficiency improvements, but few studies have considered demand reduction through efficiency ( [[#Grubler--2018|Grubler et al. 2018]] ) and the related supply implications and mitigation measures.

Five main drivers of long-term energy demand reduction that can meet the 1.5°C target include quality of life, urbanisation, novel energy services, diversification of end-user roles, and information innovation ( [[#Grubler--2018|Grubler et al. 2018]] ). A Low Energy Demand scenario requires fundamental societal and institutional transformation from current patterns of consumption, including: decentralised services and increased granularity (small-scale, low-cost technologies to provide decentralised services), increased use value from services (multi-use vs single use), sharing economies, digitalisation, and rapid transformation driven by end-user demand. This approach to transformation differs from the status quo and current climate change policies in emphasising energy end-use and services first, with downstream effects driving intermediate and upstream structural change.

Radical low-carbon innovation involves systemic, cultural, and policy changes and acceptance of uncertainty in the beginning stages. However, the current dominant analytical perspectives are grounded in neoclassical economics and social psychology, and focus primarily on marginal changes rather than radical transformations ( [[#Geels--2018|Geels et al. 2018]] ). Some literature is beginning to focus on mitigation through behaviour and lifestyle changes, but specific policy measures for supporting such changes and their contribution to emission reductions remain unclear ( [[#4.4.2|Section 4.4.2]] and Chapter 5).

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==== 4.2.5.12 Ambitious Targets to Reduce Short-lived Climate Forcers, Including Methane ====

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Recent research shows that temperature increases are likely to exceed 1.5°C during the 2030s and 2°C by mid-century unless both CO 2 and short-lived climate forcers (SLCFs) are reduced ( [[#Shindell--2017|Shindell et al. 2017]] ; [[#Rogelj--2018a|Rogelj et al. 2018a]] ). Because of their short lifetimes (days to a decade and a half), SLCFs can provide fast mitigation, potentially avoiding warming of up to 0.6°C at 2050 and up to 1.2°C at 2100 ( [[#Ramanathan--2010|Ramanathan and Xu 2010]] ; [[#Xu--2017|Xu and Ramanathan 2017]] ). In Asia especially, co-benefits of drastic CO 2 and air pollution mitigation measures reduce emissions of methane, black carbon, sulphur dioxide, nitrogen oxide, and fine particulate matter by approximately 23%, 63%, 73%, 27%, and 65% respectively in 2050 as compared to 2010 levels. Including the co-benefits of reduction of climate forcing adds significantly to the benefits reducing air pollutants ( [[#Hanaoka--2018|Hanaoka and Masui 2018]] ).

To achieve net zero GHG emissions implies consideration of targets for non-CO 2 gases. While methane emissions have grown less rapidly than CO 2 and F-gases since 1990 (Chapter 2), the literature urges action to bring methane back to a pathway more in line with the Paris goals ( [[#Nisbet--2020|Nisbet et al. 2020]] ). Measures to reduce methane emissions from anthropogenic sources are considered intractable – where they sustain livelihoods – but also becoming more feasible, as studies report the options for mitigation in agriculture without undermining food security ( [[#Wollenberg--2016|Wollenberg et al. 2016]] ; [[#Frank--2017|Frank et al. 2017]] ; [[#Nisbet--2020|Nisbet et al. 2020]] ). The choice of emission metrics has implications for SLCF ( [[#Cain--2019|Cain et al. 2019]] ) (Cross-Chapter Box 2 in Chapter 2). Ambitious reductions of methane are complementary to, rather than substitutes for, reductions in CO 2 ( [[#Nisbet--2020|Nisbet et al. 2020]] ).

Rapid SLCF reductions, specifically of methane, black carbon, and tropospheric ozone have immediate co-benefits including meeting sustainable development goals for reducing health burdens of household air pollution and reversing health- and crop-damaging tropospheric ozone ( [[#Jacobson--2002|Jacobson 2002]] , 2010). SLCF mitigation measures can have regional impacts, including avoiding premature deaths in Asia and Africa and warming in central and northern Asia, southern Africa, and the Mediterranean ( [[#Shindell--2012|Shindell et al. 2012]] ). Reducing outdoor air pollution could avoid 2.4 million premature deaths and 52 million tonnes of crop losses for four major staples ( [[#Haines--2017|Haines et al. 2017]] ). Existing research emphasises climate and agriculture benefits of methane mitigation measures with relatively small human health benefits ( [[#Shindell--2012|Shindell et al. 2012]] ). Research also predicts that black carbon mitigation could substantially benefit global climate and human health, but there is more uncertainty about these outcomes than about some other predictions ( [[#Shindell--2012|Shindell et al. 2012]] ). Other benefits to SLCF reduction include reducing warming in the critical near term, which will slow amplifying feedbacks, reduce the risk of non-linear changes, and reduce long-term cumulative climate impacts – like sea-level rise – and mitigation costs ( [[#Hu--2017|Hu et al. 2017]] ; [[#UNEP%20and%20WMO--2011|UNEP and WMO 2011]] ; [[#Rogelj--2018a|Rogelj et al. 2018a]] ; [[#Xu--2017|Xu and Ramanathan 2017]] ; [[#Shindell--2012|Shindell et al. 2012]] ).

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==== 4.2.5.13 System Analysis Solutions Are Only Beginning to Be Recognised in Current Literature on Accelerated Mitigation Pathways, and Rarely Included in Existing National Policies or Strategies ====

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Most models and studies fail to address system impacts of widespread new technology deployment, for example: (i) material and resources needed for hydrogen production or additional emissions and energy required to transport hydrogen; or (ii) materials, resources, grid integration, and generation capacity expansion limits of a largely decarbonised power sector and electrified transport sector. These impacts could limit regional and national scale-ups.

Systemic solutions are also not being sufficiently discussed, such as low-carbon materials; light-weighting of buildings, transport, and industrial equipment; promoting circular economy, recyclability and reusability, and addressing the food-energy-water nexus. These solutions reduce demand in multiple sectors, improve overall supply chain efficiency, and require cross-sector policies. Using fewer building materials could reduce the need for cement, steel, and other materials and thus the need for production and freight transport. Concrete can also be produced from low-carbon cement, or designed to absorb CO 2 from the atmosphere. Few regions have developed comprehensive policies or strategies for a circular economy, with the exception of the EU and China, and policies in the EU have only emerged within the last decade. While China’s circular economy policies emphasises industrial production, water, pollution and scaling-up in response to rapid economic growth and industrialisation, EU’s strategy is focused more narrowly on waste and resources and overall resource efficiency to increase economic competitiveness ( [[#McDowall--2017|McDowall et al. 2017]] ).

Increased bioenergy consumption is considered in many 1.5°C and 2°C scenarios. System thinking is needed to evaluate bioenergy’s viability because increased demand could affect land and water availability, food prices, and trade ( [[#Sharmina--2016|Sharmina et al. 2016]] ). To adequately address the water-energy-food nexus, policies and models must consider interconnections, synergies, and trade-offs among and within sectors, which is currently not the norm ( [[IPCC:Wg3:Chapter:Chapter-12#12.4|Section 12.4]] ).

A systems approach is also needed to support technological innovation. This includes recognising unintended consequences of political support mechanisms for technology adoption and restructuring current incentives to realise multi-sector benefits. It also entails assimilating knowledge from multiple sources as a basis for policy and decision-making ( [[#Hoolohan--2019|Hoolohan et al. 2019]] ).

Current literature does not explicitly consider systematic, physical drivers of inertia, such as capital and infrastructure needed to support accelerated mitigation ( [[#Pfeiffer--2018|Pfeiffer et al. 2018]] ). This makes it difficult to understand what is needed to successfully shift from current limited mitigation actions to significant transformations needed to rapidly achieve deep mitigation.

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