Editing IPCC:AR6/WGIII/Chapter-1 (section)

== 1.3 The Multilateral Context, Emissions Trends and Key Developments ==

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Since AR5, there have been notable multilateral efforts which help determine the context for current and future climate action. This section summarises key features of this evolving context.

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=== 1.3.1 The 2015 Agreements ===

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In 2015 the world concluded four major agreements that are very relevant to climate action. These include: the Paris Agreement under the 1992 United Nations Framework Convention on Climate Change (UNFCCC), the UN agreements on Disaster Risk Reduction (Sendai) and Finance for Development (Addis Ababa), and the Sustainable Development Goals (SDGs).

'''The Paris Agreement (PA).''' The Paris Agreement aims to ‘hold the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels’ ( [[#UNFCCC--2015|UNFCCC 2015]] ), alongside goals for adaptation (IPCC AR6 WGII), and ‘aligning financial flows’ (see ‘finance goal’, below) , so as ‘to strengthen the global response to the threat of climate change, in the context of sustainable development and efforts to eradicate poverty.’

The Paris Agreement is predicated on encouraging progressively ambitious climate action from all countries on the basis of Nationally Determined Contributions ( [[#Clémençon--2016|Clémençon 2016]] ; [[#Rajamani--2016|Rajamani 2016]] ). The NDC approach requires countries to set their own level of ambitions for climate change mitigation but within a collaborative and legally binding process to foster ambition towards the agreed goals ( [[#Bodansky--2016|Bodansky 2016]] ; [[#Falkner--2016|Falkner 2016]] a). The PA entered into force in November 2016 and as of February 2021 it already had 190 Parties (out of 197 Parties to the UNFCCC).

The PA also underlines ‘the principle of common but differentiated responsibilities and respective capabilities, in the light of different national circumstances’ (PA Art. 2, para. 2), and correspondingly that ‘developed country Parties should continue taking the lead by undertaking economy-wide absolute emission reductions’. It states that developing country Parties should continue enhancing their mitigation efforts, and are encouraged to move over time towards economy-wide emission reduction or limitation targets in the light of different national circumstances.

In order to achieve the its long term temperature goal, the Paris Agreement aims ‘to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century’ (PA Art. 4 para. 1). The PA provides for five-yearly stocktakes in which Parties have to take collective stock on progress towards achieving its purposes and its long-term goal in the light of equity and available best science (PA Art. 14). The first global stocktake is scheduled for 2023 (PA Art. 14, para. 3).

The Paris Agreement’s finance goal aims to make ‘finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development’ (PA Art. 2.1C). In keeping with the acknowledged context of global sustainable development and poverty eradication, and the corresponding aims of aligning finance and agreed differentiating principles as indicated above, ‘…the developed country parties are to assist developing country parties with financial resources’ (PA Art. 9). The Green Climate Fund (GCF), an operating entity of the UNFCCC Financial Mechanism to finance mitigation and adaptation efforts in developing countries ( [[#GCF--2020|GCF 2020]] ), was given an important role in serving the Agreement and supporting PA goals. The GCF gathered pledges worth USD10.3 billion, from developed and developing countries, regions, and one city (Paris) ( [[#Antimiani--2017|Antimiani et al. 2017]] ; [[#Bowman--2019|Bowman and Minas 2019]] ). Financing has since increased but remains short of the goal to mobilise USD100 billion by 2020 (Chapter 15).

Initiatives contributing to the Paris Agreement goals include the Non-State Actor Zone for Climate Action (NAZCA: now renamed as Global Climate Action) portal, launched at COP20 (December 2014) in Lima, Peru, to support city-based actions for mitigating climate change ( [[#IISD--2015|IISD 2015]] ) and Marrakech Partnership for Global Climate Action which is a UNFCCC-backed series of events intended to facilitate collaboration between governments and the cities, regions, businesses and investors that must act on climate change.

Details of the Paris Agreement, evaluation of the Kyoto Protocol, and other key multilateral developments since AR5 that are relevant to climate mitigation including the CORSIA aviation agreement adopted under ICAO, the IMO shipping strategy, and the Kigali Amendment to the Montreal Protocol on hydrofluorocarbons (HFCs), are discussed in Chapter 14.

'''SDGs.''' In September 2015, the UN endorsed a universal agenda – ‘Transforming our World: the 2030 Agenda for Sustainable Development’. The agenda adopted 17 non-legally-binding SDGs and 169 targets to support people, peace, prosperity, partnerships and the planet. While climate change is explicitly listed as SDG 13, the pursuit of the implementation of the UNFCCC is relevant for a number of other goals including SDG 7 (clean energy for all), SDG 9 (sustainable industry), and SDG 11 (sustainable cities), SDG 12 (responsible consumption and production) as well as those relating to life below water (SDG 14) and on land (SDG 15) ( [[#Biermann--2017|Biermann et al. 2017]] ). Mitigation actions could have multiple synergies and trade-offs across the SDGs ( [[#Pradhan--2017|Pradhan et al. 2017]] ) (Chapter 17) and their net effects depend on the pace and magnitude of changes, the specific mitigation choices and the management of the transition. This suggests that mitigation must be pursued in the broader context of sustainable development as explained in [[#1.6|Section 1.6]] .

'''Finance.''' The Paris Agreement’s finance goal (above) reflects a broadened focus, beyond the costs of climate adaptation and mitigation, to recognising that a structural shift towards low-carbon climate-resilient development pathways requires large-scale investments that engage the wider financial system (Sections 15.1 and 15.2.4). The SR1.5 report estimated that 1.5°C pathways would require ''increased investment'' of 0.5–1% of global GDP between now and 2050, which is up to 2.5% of global savings/investment over the period. For low- and middle-income countries, SDG-compatible infrastructure investments in the most relevant sectors are estimated to be around 4–5% of their GDP, and ‘infrastructure investment paths compatible with full decarbonisation in the second half of the century need not cost more than more-polluting alternatives’ ( [[#Rozenberg--2019|Rozenberg and Fay 2019]] ).

The parallel 2015 UN Addis Ababa Conference on Finance for Development, and its resulting Action Agenda, aims to ‘address the challenge of financing … to end poverty and hunger, and to achieve sustainable development in its three dimensions through promoting inclusive economic growth, protecting the environment, and promoting social inclusion.’ The Conference recognises the significant potential of regional cooperation and provides a forum for discussing the solutions to common challenges faced by developing countries ( [[#15.6.4|Section 15.6.4]] ).

Alongside this, private and blended climate finance is increasing but is still short of projected requirements consistent with Paris Agreement goals ( [[#15.3.2|Section 15.3.2]] .1). The financing gap is particularly acute for adaptation projects, especially in vulnerable developing countries. From a macro-regulatory perspective, there is growing recognition that substantial financial value may be at risk from changing regulation and technology in a low-carbon transition, with potential implications for global financial stability ( [[#15.6.3|Section 15.6.3]] ). To date, the most significant governance development is the Financial Stability Board’s Task Force on Climate-related Financial Disclosures (TCFD) and its recommendations that investors and companies consider climate change risks in their strategies and capital allocation, so investors can make informed decisions ( [[#TCFD--2018|TCFD 2018]] ), welcomed by over 500 financial institutions and companies as signatories, albeit with patchy implementation (Sections 1.4. 4 and 15.6.3).

'''Talanoa Dialogue and Just Transition.''' Asmandated at Paris COP21 and launched at COP23, the ‘Talanoa Dialogue’ ( [[#UNFCCC--2018a|UNFCCC 2018a]] ) emphasised holistic approaches across multiple economic sectors for climate change mitigation. At COP24 also, the Just Transition Silesia Declaration, focusing on the need to consider social aspects in designing policies for climate change mitigation was signed by 56 heads of state ( [[#UNFCCC--2018b|UNFCCC 2018b]] ). This underlined the importance of aiming for Just Transitions in reducing emissions, at the same time preserving livelihoods and managing economic risks for countries and communities that rely heavily on emissions-intensive technologies for domestic growth ( [[#Markkanen--2019|Markkanen and Anger-Kraavi 2019]] ), and for maintaining ecosystem integrity through nature-based solutions.

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=== 1.3.2 Global and Regional Emissions ===

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Global GHG emissions have continued to rise since AR5, though the average rate of emissions growth slowed, from 2.4% (from 2000–2010) to 1.3% for 2010–2019 (Figure 1.1). After a period of exceptionally rapid growth from 2000 as charted in AR5, global fossil fuel- and industry-related (FFI) CO 2 emissions almost plateaued between 2014 and 2016 (while the global economy continued to expand ( [[#World%20Bank--2020|World Bank 2020]] ), but increased again over 2017–19, the average annual growth rate for all GHGs since 2014 being around 0.8% yr –1 (IPCC/EDGAR emissions database; see also Chapter 11, Figure 11.2)). Important driving factors include population and GDP growth, as illustrated in panels (b) and (c) of Figure 1.1 respectively. The pause in emissions growth reflected the interplay of strong energy efficiency improvements and low-carbon technology deployment, butthese did not expand fast enough to offset the continued pressures for overall growth at global level ( [[#UNEP--2018a|UNEP 2018a]] ; [[#IEA--2019a|IEA 2019a]] ). However, since 2013/14, the decline in global emissions intensity (GHG/GDP) has accelerated somewhat, and global emissions growth has averaged slightly slower than population growth (Figure 1.1d), which if sustained would imply a peak of global CO 2 (GHG) emissions per capita, at about 5 tCO 2 per person (7 tCO 2 -eq per person) respectively.

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'''Figure 1.1 | Global emission trends since 2000 by groups of gases: absolute, per capita, and intensity.''' Note: shows CO 2 from fossil fuel combustion and industrial processes (FFI); CO 2 from agriculture, forestry and other land use (AFOLU); methane (CH 4 ); nitrous oxide (N 2 O); fluorinated gases (F-gases). Gases reported in GtCO 2 -eq converted based on AR6 global warming potentials with a 100-year time horizon (GWP100).

Due to its much shorter lifetime, methane has a disproportionate impact on near-term temperature, and is estimated to account for almost a third of the warming observed to date (AR6 WGI SPM; AR6 WGIII Chapter 2, Figure 2.4). Methane reductions could be particularly important in relation to near- and medium-term temperatures, including through counteracting the impact of reducing short-lived aerosol pollutants which have an average cooling effect. [[#footnote-007|2]]

The land-use component of CO 2 emissions has different drivers and particularly large uncertainties (Figures 2.2 and 2.5), hence is shown separately. Also, compared to AR5, new evidence showed that the AFOLU CO 2 estimates by the global models assessed in this report are not necessarily comparable with national GHG inventories, due to different approaches to estimate the ‘anthropogenic’ CO 2 sink. Possible ways to reconcile these discrepancies are discussed in Chapter 7.

Regional trends have varied. Emissions from most countries continued to grow, but in absolute terms, 32 countries reduced energy and industry CO 2 emissions for at least a decade, and 24 reduced overall GHG (CO 2 -eq) emissions over the same period, but only half of them by more than 10% over the period in each case (Chapter 2). [[#footnote-006|3]] In total, developed country emissions barely changed from 2010, whilst those from the rest of the world grew.

Figure 1.2 shows the distribution of regional emissions (a) per capita and (b) per GDP based on purchasing power parity (GDP ppp ) of different country groupings in 2019. Plotted against population and GDP respectively, the area of each block is proportional to the region’s emissions. Compared to the equivalent presentations in 2004 (AR4 WGIII Figure SPM.3) and 2010 (AR5 WGIII Figure 1.8), East Asia now forms substantially the biggest group, whilst at about 8 tCO 2 -FFI (/10 tCO 2 -eq all GHGs) per person, its emissions per capita remain about half that of North America. In contrast, a third of the world’s population, in Southern Asia and Africa, emit on average under 2 (2.5 tCO 2 -eq) per person, little more than in the previous assessments. Particularly for these regions, there continue to be substantial differences in GDP, life expectancy and other measures of well-being (Figure 1.6).

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'''Figure 1.2 | Distribution of regional greenhouse gas (GHG) emissions for 10 broad global regions according to territorial accounting (panels (a) and (b), GHG emissions) and consumption-based accounting (panels (c) and (d), CO''' 2 '''-FFI emissions only).''' GHG emissions are categorised into: fossil fuel and industry (CO 2 -FFI); land use, land-use change and forestry (CO 2 -LULUCF); and other greenhouse gases (methane, nitrous oxide and F-gas – converted to 100-year global warming potentials). Per-capita GHGs for territorial '''(panel a)''' and CO 2 -FFI emissions vs population for consumption-based accounting '''(panel c)''' . Panels '''(b)''' and '''(d)''' : GHG emissions per unit GDP ppp vs GDP ppp , weighted with purchasing power parity for territorial accounting (panel b), CO 2 -FFI emissions per unit GDP ppp for consumption-based accounting (panel d). The area of the rectangles refers to the total emissions for each regional category, with the height capturing per-capita emissions (panels a and c) or emissions per unit GDP ppp (panels (b) and (d)), and the width proportional to the population of the regions and GDP ppp . Emissions from international aviation and shipping (2.4% of the total GHG emissions) are not included.

''Emissions'' ''per unit GDP'' are much less diverse than per capita and have also converged significantly. Poorer countries tend to show higher energy/emissions per unit GDP partly because of higher reliance on basic industries, and this remains the case, though in general their energy/GDP has declined faster.

Many developed country regions are net importers of energy-intensive goods, and emissions are affected by the accounting of such ‘embodied emissions’. Panels (c) and (d) show results (only available for CO 2 -FFI, to 2018) on the basis of consumption footprints which include emissions embodied in traded goods. This makes modest changes to the relative position of different regions (for further discussion see [[IPCC:Wg3:Chapter:Chapter-2#2.3|Section 2.3]] ).

While extreme poverty has fallen in more than half of the world’s economies in recent years, nearly one fifth of countries faced poverty rates above 30% in 2015 (below USD1.90 a day), reflecting large income inequality ( [[#Laborde%20Debucquet--2017|Laborde Debucquet and Martin 2017]] ; [[#Rozenberg--2019|Rozenberg and Fay 2019]] ). [[#Diffenbaugh--2019|Diffenbaugh and Burke (2019)]] find that global warming already has increased global economic inequality, even if between-country inequalities have decreased over recent decades. The distributional implications between regional groups in the Shared Socio-economic Pathways (SSPs) diverge according to the scenario ( [[#Frame--2019|Frame et al. 2019]] ).

An important recent development has been commitments by many countries, now covering a large majority of global emissions, to reach net zero CO 2 or greenhouse gas emissions (Chapter 3). [[#footnote-005|4]] Furthermore, globally, net zero targets (whether CO 2 or GHG) have been adopted by about 823 cities and 101 regions (Chapter 8).

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=== 1.3.3 Some Other Key Trends and Developments ===

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The COVID-19 pandemic profoundly impacted economy and human society, globally and within countries. As detailed in Cross-Chapter Box 1 in this chapter, some of its impacts will be long-lasting, permanent even, and there are also lessons relevant to climate change. The direct impact on emissions projected for rest of this decade are modest, but the necessity for economic recovery packages creates a central role for government-led investment, and may change the economic fundamentals involved for some years to come.

The COVID-19 aftermath consequently also changes the economic context for mitigation (Sections 15.2 and 15.4). Many traditional forms of economic analysis (expressed as general equilibrium) assume that available economic resources are fully employed, with limited scope for beneficial economic ‘multiplier effects’ of government-led investment. After COVID-19 however, no country is in this state. Very low interest rates amplify opportunities for large-scale investments which could bring ‘economic multiplier’ benefits, especially if they help to build the industries and infrastructures for further clean growth ( [[#Hepburn--2020|Hepburn et al. 2020]] ). However, the capability to mobilise low-interest finance varies markedly across countries and large public debts – including bringing some developing countries close to default – undermine both the political appetite and feasibility of large-scale clean investments. In practice the current orientation of COVID-19 recovery packages is very varied, pointing to a very mixed picture about whether or not countries are exploiting this opportunity (Cross-Chapter Box 1 in this chapter).

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=== Cross-Chapter Box 1 | The COVID-19 Crisis: Lessons, Risks and Opportunities for Mitigation ===

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'''Authors:''' Diana Ürge-Vorsatz (Hungary), Lilia Caiado Couto (Brazil), Felix Creutzig (Germany), Dipak Dasgupta (India), Michael Grubb (United Kingdom), Kirsten Halsnæs (Denmark), Şiir Kılkış (Turkey), Alexandre Köberle (Brazil/United Kingdom), Silvia Kreibiehl (Germany), Jan Christoph Minx (Germany), Peter Newman (Australia), Chukwumerije Okereke (Nigeria/United Kingdom)

The COVID-19 pandemic triggered the deepest global economic contraction as well as CO 2 emission reductions since the Second World War ( [[#Le%20Quéré--2020|Le Quéré et al. 2020]] b), (AR6 WGI, Box 6.1) ( [[IPCC:Wg3:Chapter:Chapter-2#2.2.2.1|Section 2.2.2.1]] ). While emissions and most economies are expected to rebound in 2021–2022 ( [[#IEA--2021|IEA 2021]] ) , some impacts of the pandemic (e.g., aspects of economy, finance and transport-related emission drivers) may last far longer. COVID-19 pushed more than 100 million people back into extreme poverty, and reversed progress towards some other SDGs including health, life expectancy and child literacy ( [[#UN%20DESA--2021|UN DESA 2021]] ) . Health impacts and the consequences of deep economy-wide shocks may last many years even without significant future recurrence ( [[#15.6.3|Section 15.6.3]] ). These changes, as well as the pandemic response actions, bring both important risks as well as opportunities for accelerating mitigation (Chapters 1, 5, 10 and 15).

Cross-Chapter Box 1

'''Lessons.''' Important lessons can be drawn from the pandemic to climate change including the value of forward-looking risk management, the role of scientific assessment, preparatory action and international process and institutions ( [[IPCC:Wg3:Chapter:Chapter-5|Chapter 5]] and [[#1.3|Section 1.3]] ). There had been long-standing warnings of pandemic risks and precursors – with both pandemic and climate risks being identified by social scientists as ‘uncomfortable knowledge’ or ‘unknown knowns’, which tend to be marginalised in practical policy ( [[#Rayner--2012|Rayner 2012]] ; [[#Sarewitz--2020|Sarewitz 2020]] ) . This echoes long-standing climate literature on potential ‘high impact’ events, including those ''perceived'' as low probability ( [[#Dietz--2011|Dietz 2011]] ; [[#Weitzman--2011|Weitzman 2011]] ) . The costs of preparatory action, mainly in those countries that had suffered from earlier pandemics were negligible in comparison, suggesting the importance not just of knowledge but its effective communication and embodiment in society (Chapter 5). Klenert et al. (2020) offer five early lessons for climate policy, concerning: the cost of delay; the bias in human judgement; the inequality of impacts; the need for multiple forms of international cooperation; and finally, ‘transparency in value judgements at the science–policy interface’.

'''Emissions and behavioural changes.''' Overall, global CO 2 FFI emissions declined by about 5.8% (5.1–6.3%) from 2019 to 2020, or about 2.2 (1.8–2.4) GtCO 2 in total ( [[IPCC:Wg3:Chapter:Chapter-2#2.2.2|Section 2.2.2]] ). Analysis from previous economic crises suggest significant rebound in emissions without policy-induced structural shifts ( [[#Jaeger--2020|Jaeger et al. 2020]] ) ( [[IPCC:Wg3:Chapter:Chapter-2#2.2.2.1|Section 2.2.2.1]] and Figure 2.5). Initial projections suggest the COVID aftermath may reduce emissions by 4–5% over 2025–2030 (Shan and Et.al 2020; [[#Reilly--2021|Reilly et al. 2021]] ), below a ‘no-pandemic’ baseline. The long-term impacts on behaviour, technology and associated emissions remain to be seen, but may be particularly significant in transport – lockdowns reduced mobility-related emissions, alongside two major growth areas: electronic communications replacing many work and personal travel requirements ( [https://www.ipcc.ch/report/ar6/wg3/chapter/chapter-10 Chapter 10] and [[IPCC:Wg3:Chapter:Chapter-4#4.4.3.4|Section 4.4.3.4]] ); and revitalised local active transport and e-micromobility ( [[#Earley--2021|Earley and Newman 2021]] ). Temporary ‘clear skies’ may also have raised awareness of the potential environment and health co-benefits of reduced fossil fuel use particularly in urban areas ( [[IPCC:Wg3:Chapter:Chapter-8#8.7|Section 8.7]] ), with evidence also indicating that air pollution itself amplified vulnerability to COVID-19 ( [[#Gudka--2020|Gudka et al. 2020]] ; [[#Wu--2020|Wu et al. 2020]] ). The significant impacts on passenger aviation are projected to extend not just through behavioural changes, but also fleet changes from retiring older planes, and reduced new orders indicating expectations of reduced demand and associated GHG emissions until 2030 (Sections 5.1.2 and 10.5) (AR6 WGI Box 6.1 in Chapter 6). However, air cargo has recovered more rapidly ( [[#IATA--2020|IATA 2020]] ), possibly enhanced by online ordering.

'''Fiscal, growth and inequality impacts.''' Aspects of the global and regional economic crises from COVID-19 may prevail much longer than the crisis itself, potentially compromising mitigation. M ost countries have undertaken unprecedented levels of short-term public expenditures. The International MonetaryFund (IMF) projects sovereign debt to GDP to have increased by 20% in advanced economies and 10% in emerging economies by the end of 2021 ( [[#IMF--2020|IMF 2020]] ). This is likely to slow economic growth, and may squeeze financial resources for mitigation and relevant investments for many years to come (Sections 15.2.3 and 15.6.3). COVID-19 further lowered interest rates which should facilitate low-carbon investment, but pandemic responses have increased sovereign debt across countries in all income bands ( [[#IMF--2021|IMF 2021]] ), and, particularly in some developing economies and regions, it has caused debt distress (Bulow et al. 2021), widening the gap in developing countries’ access to capital (Hourcade et al. 2021b) ( [[#15.6.3|Section 15.6.3]] ). After decades of global progress in reducing poverty, COVID-19 has pushed hundreds of millions of people below poverty thresholds and raises the spectre of intersecting health and climate crises that are devastating for the most vulnerable ( [[IPCC:Wg3:Chapter:Chapter-5#5.1|Section 5.1]] .2 and Box 5.1). Like those of climate change, pandemic impacts fall heavily on disadvantaged groups, exacerbate the uneven distribution of future benefits, amplify existing inequities, and introduce new ones . Increased poverty also hinders efforts towards sustainable low-carbon transitions ( [[#1.6|Section 1.6]] ).

'''Impacts on profitability and investment.''' COVID-19-induced demand reduction in electricity disproportionally affected coal power plants, whilst transport reduction most affected oil ( [[#IEA--2020a|IEA 2020a]] ) . This accelerated pre-existing decline in the relative profitability of most fossil fuel industries (Ameli et al. 2021) . Renewables were the only energy sector to increase output ( [[#IEA--2020a|IEA 2020a]] ) . Within the context of a wider ''overall'' reduction in energy investment this prompted a substantial ''relative'' shift towards low-carbon investment particularly by the private sector ( [[#IEA--2020b|IEA 2020b]] ; [[#Rosembloom--2020|Rosembloom and Markard 2020]] ) (Sections 15.2.1, 15.3. 1 and 15.6.1) .

'''Post-pandemic recovery pathways provide an opportunity to attract finance into accelerated and transformative low-carbon public investment (Sections 15.2 and 15.6.3).''' In most countries, COVID-19 has increased unemployment and/or state-supported employment. There is a profound difference between short-term ‘bail outs’ to stem unemployment, and the orientation of new public investment. The public debt is mirrored by large pools of private capital. D uring deep crises like that of COVID-19, economic multipliers of stimulus packages can be high ( [[#Hepburn--2020|Hepburn et al., 2020]] ), so much so that fiscal injections can then generate multipliers from 1.5 to 2.5, weakening the alleged crowding-out effect of public stimulus ( [[#Auerbach--2012|Auerbach and Gorodnichenko 2012]] ; [[#Blanchard--2013|Blanchard and Leigh 2013]] ) ( [[#15.2.3|Section 15.2.3]] ).

Cross-Chapter Box 1

Recovery packages are motivated by assessments of the macroeconomic effectiveness (‘multipliers’) of public spending in ways that can crowd-in and revive private investment (Hepburn et al. 2020 ). There are clear reasons why a low-carbon response can create more enduring jobs, better aligned to future growth sectors: by also crowding-in and reviving private investment (e.g., from capital markets and institutional investors, including the growing profile of environmental, social and governance (ESG) and green bond markets ( [[#15.6|Section 15.6]] )), this can boost the effectiveness of public spending ( [[#IMF--2020|IMF 2020]] ) . Stern and Valero (2021) argue that investment in low-carbon innovation and its diffusion, complemented by investments in sustainable infrastructure, are key to shaping environmentally sustainable and inclusive growth in the aftermath of the COVID-19 pandemic crisis. This would be the case both for high-income economies on the global innovation frontier, and to promote sustainable development in poorer economies.

A study with a global general equilibrium model (Liu et al. 2021) finds that because the COVID-19 economic aftermath combines negative impacts on employment and consumption, a shift from employment and consumption taxes to carbon- or other resource-related taxes would enhance GDP by 1.7% in 2021 relative to ‘no policy’, in addition to reducing CO 2 and other pollutants. A post-Keynesian model of wider ‘green recovery’ policies (Pollitt et al. 2021) finds a short-run benefit of around 3.5% GDP (compared to ‘no policy’), and even about 1% above a recovery boosted by cuts in consumption taxes, the latter benefit sustained through 2030 – outperforming an equivalent conventional stimulus package while reducing global CO 2 emissions by 12%.

'''Orientation of recovery packages.''' The large public spending on supporting or stimulating economies, exceeding USD12 trillion by October 2020, dwarfs clean-energy investment needs and hence could either help to solve the combined crises, or result in high-carbon lock-in (Andrijevic et al. 2020) . The short-term ‘bail outs’ to date do not foster climate-resilient long-term investments and have not been much linked to climate action, (Sections 15.2.3 and 15.6.3): in the G20 counties, 40% of energy-related support spending went to the fossil fuel industry compared to 37% on low-carbon energy ( [[#EPT--2020|EPT 2020]] ) . Recovery packages are also at risk of being ‘colourless’ ( [[#Hepburn--2020|Hepburn et al., 2020]] ), though some countries and regions have prioritised green stimulus expenditures for example as part of a ‘Green New Deal’ (Rochedo et al. 2021) (Sections 13.9 .6 and 15.6.3) .

'''Integrating analyses.''' The response to COVID-19 also reflects the relevance of combining multiple analytic frameworks spanning economic efficiency, ethics and equity, transformation dynamics, and psychological and political analyses ( [[#1.7|Section 1.7]] ). As with climate impacts, not only has the global burden of disease been distributed unevenly, but capabilities to prevent and treat disease were asymmetrical and those in greatest vulnerability often had the least access to human, physical, and financial resources ( [[#Ruger--2020|Ruger and Horton 2020]] ) . ‘Green’ versus ‘brown’ recovery has corresponding distributional consequences between these and ‘green’ producers, suggesting need for differentiated policies with international coordination (Le Billon et al. 2021) . This illustrates the role of Just Transition approaches to global responses including the value of integrated, multi-level governance (Sections 1.7, 4.5 and 17.1).

'''Crises and opportunities: the wider context for mitigation and transformation.''' The impacts of COVID-19 have been devastating in many ways, in many countries, and may distract political and financial capacity away from efforts to mitigate climate change. Yet, studies of previous post-shock periods suggest that waves of innovation that are ready to emerge can be accelerated by crises, which may prompt new behaviours, weaken incumbent (‘meso-level’) systems, and prompt rapid reforms (Roberts and Geels 2019a) ( [[#1.6|Section 1.6]] .5) . Lessons from the collective effort to ‘flatten the curve’ during the pandemic, illustrating aspects of science–society interactions for public health in many countries, may carry over to climate mitigation, and open new opportunities ( [[IPCC:Wg3:Chapter:Chapter-5#5.1|Section 5.1]] .2). COVID-19 appears to have accelerated the emergence of renewable power, electromobility and digitalisation ( [[#Newman--2020|Newman 2020]] ) (Sections 5.1.2, 6.3 and 10.2) . Institutional change is often very slow but major economic dislocation can create significant opportunities for new ways of financing and enabling ‘leapfrogging’ investment to happen ( [[#10.8|Section 10.8]] ). Given the unambiguous risks of climate change, and consequent stranded asset risks from new fossil fuel investments (Box 6.11), the most robust recoveries are likely to be those which emerge on lower carbon and resilient pathways (Obergassel et al. 2021) . Noting the critical global post-COVID-19 challenge as the double impact of heightened credit risk in developing countries, along with indebtedness in developed countries, Hourcade et al. (2021a) estimate that a ‘multilateral’ sovereign guarantee structure to underwrite low-carbon investments could leverage projects up to 15 times its value, contributing to shifting development pathways consistent with the SDGs and Paris goals.

COVID- 19 can thus be taken as a reminder of the urgency of addressing climate change, a warning of the risk of future stranded assets (Rempel and Gupta 2021) (Chapter 17), but also an opportunity for a cleaner recovery.

In addition to developments in climate science, emissions,the international agreements in 2015, and the recent impact of COVID-19, a few other key developments have strong implications for climate mitigation.

'''Cheaper renewable energy technologies.''' Most striking, the cost of solar photovoltaic (PV) has fallen by a factor of 5 to 10 in the decade since the IPCC Special Report on Renewable Energy ( [[#IPCC--2011a|IPCC 2011a]] ) and other data inputting to the AR5 assessments. The SR1.5 reported major cost reductions, the IEA (2020) World Energy Outlook described PV as now ‘the cheapest electricity in history’ for projects that ‘tap low cost finance and high quality resources.’ Costs and deployment both vary widely between different countries (Chapters 6, 9 and 12) but costs are still projected to continue falling ( [[#Vartiainen--2020|Vartiainen et al. 2020]] ). Rapid technological developments have occurred in many other low-carbon technologies including batteries and electric vehicles ( [[#1.4.3|Section 1.4.3]] ), IT and related control systems, with progress also where electrification is not possible (Chapters 2, 6 and 11).

'''Civil society pressures for stronger action.''' Civic engagement increased leading up to the Paris Agreement ( [[#Bäckstrand--2019|Bäckstrand and Lövbrand 2019]] ) and after. Youth movements in several countries show young people’s awareness about climate change, evidenced by the school strikes for the climate ( [[#Hagedorn--2019|Hagedorn et al. 2019]] ; [[#Buettner--2020|Buettner 2020]] ; [[#Thackeray--2020|Thackeray et al. 2020]] ; [[#Walker--2020|Walker 2020]] ). Senior figures across many religions ( [[#Francis--2015|Francis 2015]] ; [[#IFEES--2015|IFEES 2015]] ) stressed the duty of humanity to protect future generations and the natural world, and warned about the inequities of climate change. Growing awareness of local environmental problems such as air pollution in Asia and Africa ( [[#Karlsson--2020|Karlsson et al. 2020]] ), and the threat to indigenous people’s rights and existence has also fuelled climate activism ( [[#Etchart--2017|Etchart 2017]] ). Grass-roots movements ( [[#Cheon--2018|Cheon and Urpelainen 2018]] ; [[#Fisher--2019|Fisher et al. 2019]] ), build political pressure for accelerating climate change mitigation, as does increasing climate litigation ( [[#Setzer--2019|Setzer and Vanhala 2019]] ) (Chapters 13 and 14).

'''Climate policies also encounter resistance''' . However, there are multiple sources of resistance to climate action in practice. Corporations and trade associations often lobby against measures they deem detrimental ( [[#1.4.6|Section 1.4.6]] ). The emblematic ‘yellow vest’ movement in France was triggered by higher fuel costs as a result of a CO 2 tax hike ( [[#Lianos--2019|Lianos 2019]] ; [[#Driscoll--2021|Driscoll 2021]] ), though it had broader aspect of income inequality and other social issues. There is often a mismatch between concerns on climate change and people’s willingness to pay for mitigation. For example, whilst most Americans believe climate change is happening, 68% said in a survey they would oppose climate policies that added just USD10 per month to electricity bills (EPIC et al. 2019), and worry about energy costs can eclipse those about climate change elsewhere ( [[#Poortinga--2018|Poortinga et al. 2018]] ) (Chapter 13).

'''Global trends contrary to multilateral cooperation.''' State-centred politics and geopolitical/geo-economic tensions seem to have become more prominent across many countries and issues ( [[#WEF--2019|WEF 2019]] ). In some cases, multilateral cooperation could be threatened by trends such as rising populism, nationalism, authoritarianism and growing protectionism ( [[#Abrahamsen--2019|Abrahamsen et al. 2019]] ), making it more difficult to tackle global challenges including protecting the environment ( [[#Schreurs--2016|Schreurs 2016]] ; [[#Parker--2017|Parker et al. 2017]] ; [[#WEF--2019|WEF 2019]] ).

'''Transnational alliances.''' Partly countering this trend, cities, businesses and a wide range of other non-state actors also have emerged with important international networks to foster mitigation. City-based examples include the Cities Alliance in addressing climate change, Carbon Neutral Cities Alliance and the Covenant of Mayors (Chapter 8); there are numerous other alliances and networks such as those in finance (Chapter 15) and technology (Chapter 16), amongst many others (Chapters 13 and 14).

Finally, under the Paris Agreement process, during 2020/21, many countries strengthened their Nationally Determined Contributions (NDCs). Including updates until October 2021, these would imply global GHG emissions declining by 2030 to between 1–4% below 2019 levels (unconditional NDCs), or 4–10% (for NDCs conditional on international support) (Table 4.3). This is a significant change but would still not be compatible with 1.5°C pathways, and even if delivered in full, to limit warming to 2°C (&gt;67%), emissions would have to fall very rapidly after 2030 ( [[IPCC:Wg3:Chapter:Chapter-3#3.2.5|Section 3.2.5]] ).

Thus, developments since AR5 highlight the complexity of the mitigation challenge. There is no far-sighted, globally optimising decision-maker and indeed climate policymaking at all levels is subject to conflicting pressures in multiple ways. The next section overviews the drivers and constraints.

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