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

== 1.1 Introduction ==

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This report (AR6 WGIII) aims to assess new literature on climate mitigation including implications for global sustainable development. In this Sixth Assessment Cycle the IPCChas also published three Special Reports, [[#footnote-008|1]] all of which emphasise the rising threat of climate change and the implications for more ambitious mitigation efforts at all scales. At the same time, the Paris Agreement (PA) and the UN 2030 Agenda for Sustainable Development with its 17 Sustainable Development Goals (SDGs), both adopted in 2015, set out a globally agreed agenda within which climate mitigation efforts must be located. Along with a better understanding of the physical science basis of climate change (AR6 WGI), and vulnerabilities, impacts, and adaptation (AR6 WGII), the landscape of climate mitigation has evolved substantially since the Fifth Assessment Report (AR5).

Since ( [[#IPCC--2014a|IPCC 2014a]] ), climate mitigation policies around the world have grown in both number and shape (Chapter 13). However, while the average rate of annual increase of CO 2 emissions has declined ( [[#1.3.2|Section 1.3.2]] ), GHG emissions globally continued to rise, underlining the urgency of the mitigation challenge (Chapters 2 and 3). Over 20 countries have cut absolute emissions alongside sustained economic growth, but the scale of mitigation action across countries remains varied and is generally much slower than the pace required to meet the goals of the Paris Agreement (Sections 1.3.2 and 2.7.2). Per capita GHG emissions between countries even at similar stages of economic development (based on GDP per capita) vary by a factor of three (Figure 1.6) and by more than two on consumption basis ( [[IPCC:Wg3:Chapter:Chapter-2#2.3|Section 2.3]] ).

The Special Report on Global Warming of 1.5°C (SR1.5) underlined that humanity is now living with the ‘unifying lens of the Anthropocene’ ( [[#IPCC--2018a|IPCC 2018a]] , pp. 52–53), that requires a sharpened focus on the impact of human activity on the climate system and the planet more broadly given ‘planetary boundaries’ (Steffen et al. 2015) including interdependencies of climate change and biodiversity (Dasgupta 2021). Recent literature assessed by Working Groups I and II of this AR6 underlines the urgency of climate action as cumulative CO 2 emissions, along with other greenhouses gases (GHGs), drives the temperature change. Across AR6, global temperature changes are defined relative to the period 1850–1900, as in SR1.5 and collaboration with WGI enabled the use of AR6-calibrated emulators to assure consistency across the three Working Groups. The remaining ‘carbon budgets’ (see Annex I: Glossary) associated with 1.5°C and 2°C temperature targets equate to about one (for 1.5°C) to three (for 2°C) decades of current emissions, as from 2020, but with significant variation depending on multiple factors including other gases (Figure 2.7, and Cross-Working Group Box 1 in Chapter 3). For an outline of the WGIII approach to mitigation scenarios, emission pathways implied by the Paris goals, and the timing of peak and ‘net zero’ (see Glossary and FAQ 1.3), see [[#1.5|Section 1.5]] and Chapter 3.

Strong differences remain in responsibilities for, and capabilities to, take climate action within and between countries. These differences, as well as differences in the impact of climate change, point to the role of collective action in achieving urgent and ambitious global climate mitigation in the context of sustainable development, with attention to issues of equity and fairness as highlighted in several chapters of the report (Chapters 4, 5, 14, 15 and 17).

Innovation and industrial development of key technologies in several relevant sectors have transformed prospects for mitigation at much lower cost than previously assessed (Chapters 2 and 6–12). Large reductions in the cost of widely available renewable energy technologies, along with energy efficient technologies and behavioural changes (Chapters 5 and 9–11), can enable societies to provide services with much lower emissions. However, there are still significant differences in the ability to access and utilise low-carbon technologies across the world (Chapters 4, 15 and 16). New actors, including cities, businesses, and numerous non-state transnational alliances have emerged as important players in the global effort to tackle climate change (Chapters 13–16).

Along with continued development of concepts, models and technologies, there have been numerous insights from both the successes and failures of mitigation action that can inform future policy design and climate action. However, to date, policies and investments are still clearly inadequate to put the world in line with the PA’s aims (Chapters 13 and 15).

The greater the inertia in emission trends and carbon-intensive investments, the more that CO 2 will continue to accumulate ( [[#Hilaire--2019|Hilaire et al. 2019]] ; [[#IPCC--2019a|IPCC 2019a]] ). Overall, the literature points to the need for a more dynamic consideration of intertwined challenges concerning the transformation of key GHG-emitting systems: to minimise the trade-offs, and maximise the synergies, of delivering deep decarbonisation whilst enhancing sustainable development.

This chapter introduces readers to the AR6 WGIII Report and provides an overview of progress and challenges, in three parts. Part A (1.1–1.5) introduces the climate mitigation challenge, provides key findings and developments since previous assessment, and reviews the main drivers for, and constraints against accelerated climate action. Part B (1.6–1.8) provides an assessment of the key frameworks for understanding the climate mitigation challenge covering broad approaches such as sustainable development and more specific economic, political and ethical framings. Part C (1.9–1.12) briefly highlights the role of governance for steering and coordinating efforts to accelerate globally effective and equitable climate mitigation, notes the gaps in knowledge that have been identified in the process of assessment, and provides a road map to the rest of the report.

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