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

=== 1.1.1 The AR6 WGI Report ===

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The Sixth Assessment Report (AR6) of the IPCC marks more than 30 years of global collaboration to describe and understand, through expert assessments, one of the defining challenges of the 21st century: human-induced climate change. Since the inception of the IPCC in 1988, our understanding of the physical science basis of climate change has advanced markedly. The amount and quality of instrumental observations and information from paleoclimate archives have substantially increased. Understanding of individual physical, chemical and biological processes has improved. Climate model capabilities have been enhanced, through the more realistic treatment of interactions among the components of the climate system, and improved representation of the physical processes, in line with the increased computational capacities of the world’s supercomputers.

This Report assesses both observed changes, and the components of these changes that are attributable to anthropogenic influence (i.e., human-induced), distinguishing between anthropogenic and naturally forced changes (Chapter 3, Sections [[#1.2.1.1|1.2.1.1]] and [[#1.4.1|1.4.1]] , and the Cross-Working Group Box on Attribution). The core assessment conclusions from previous IPCC reports are confirmed or strengthened in this report, indicating the robustness of our understanding of the primary causes and consequences of anthropogenic climate change.

The WGI contribution to AR6 is focused on physical and biogeochemical climate science information, with particular emphasis on regional climate changes. These are relevant for mitigation, adaptation and risk assessment in the context of complex and evolving policy settings, including the Paris Agreement, the global stocktake, the Sendai Framework and the Sustainable Development Goals (SDGs) Framework.

The core of this report consists of 12 chapters plus the [[IPCC:Wg1:Chapter:Atlas|Atlas]] (Figure 1.1), which can together be grouped into three categories (excluding this framing chapter):

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[[File:99f437809496408df2aaa7993979df85 IPCC_AR6_WGI_Figure_1_1.png]]

'''Figure 1.1 |''' '''The structure of the AR6 WGI Report''' . Shown are the three pillars of the AR6 WGI, its relation to the WGII and WGIII contributions, and the cross-working-group AR6 Synthesis Report (SYR).

'''Large-scale Information (Chapters 2, 3 and 4).''' These chapters assess climate information from global to continental or ocean-basin scales. [[IPCC:Wg1:Chapter:Chapter-2|Chapter 2]] presents an assessment of the changing state of the climate system, including the atmosphere, biosphere, ocean and cryosphere. [[IPCC:Wg1:Chapter:Chapter-3|Chapter 3]] continues with an assessment of the human influence on this changing climate, covering the attribution of observed changes, and introducing the fitness-for-purpose approach for the evaluation of climate models used to conduct the attribution studies. Finally, [[IPCC:Wg1:Chapter:Chapter-4|Chapter 4]] assesses climate change projections, from the near to the long term, including climate change beyond 2100, as well as the potential for abrupt and ‘low-likelihood, high-impact’ outcomes.

'''Process Understanding (Chapters 5, 6, 7, 8 and 9).''' These five chapters provide end-to-end assessments of fundamental Earth system processes and components: the carbon budget and biogeochemical cycles (Chapter 5), short-lived climate forcers and their links to air quality (Chapter 6), the Earth’s energy budget and climate sensitivity (Chapter 7), the water cycle (Chapter 8), and the ocean, cryosphere and sea level changes (Chapter 9). All these chapters provide assessments of observed changes, including relevant paleoclimatic information and understanding of processes and mechanisms as well as projections and model evaluation.

'''Regional Information (Chapters 10, 11, 12 and Atlas).''' New knowledge on climate change at regional scales is reflected in this report with four chapters covering regional information. [https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-10 Chapter 10] provides a framework for assessment of regional climate information, including methods, physical processes, an assessment of observed changes at regional scales, and the performance of regional models. [https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-11 Chapter 11] addresses extreme weather and climate events, including temperature, precipitation, flooding, droughts and compound events. [https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-12 Chapter 12] provides a comprehensive, region-specific assessment of changing climatic conditions that may be hazardous or favourable (hence influencing climate risk) for various sectors to be assessed in WGII. Lastly, the [[IPCC:Wg1:Chapter:Atlas|Atlas]] assesses and synthesizes regional climate information from the whole report, focussing on the assessments of mean changes in different regions and on model assessments for the regions. It also introduces the online Interactive Atlas, a novel compendium of global and regional climate change observations and projections. It includes a visualization tool, which combines various warming levels and scenarios on multiple scales of space and time.

Embedded in the chapters are '''Cross-Chapter Boxes''' that highlight cross-cutting issues. Each chapter also includes an '''Executive Summary (ES),''' and several '''Frequently Asked Questions (FAQs)''' . To enhance traceability and reproducibility of report figures and tables, detailed information on the input data used to create them, as well as links to archived code, are provided in The '''Input Data Tables''' in chapter '''Supplementary Material''' . Additional metadata on the model input datasets is provided via the report website ( https://www.ipcc.ch/assessment-report/ar6/ ).

The AR6 WGI Report includes a '''Summary for Policymakers (SPM)''' and a '''Technical Summary (TS)''' . The integration among the three IPCC Working Groups is strengthened by the inclusion of The '''Cross-Working-''' '''Group Glossary''' .

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