Climate Change 2021: The Physical Science Basis: Summary for Policymakers

Abstract

The Working Group I contribution to the Intergovernmental Panel on Climate Change’s Sixth Assessment Report assesses the physical science basis of climate change, primarily built from the executive summaries of individual chapters and backed by various lines of evidence such as observation analyses, models, paleoclimate information, and understanding of the climatic system’s physical, chemical, and biological processes. It communicates the certainty levels in key findings using two calibrated approaches - confidence and likelihood. The Report includes the context and progress in climate science, information on past and future large-scale climate changes, and an understanding of climate forcings, feedback, and responses. The findings are supported by an interactive online tool called the WGI Interactive Atlas, which complements the report by providing analyses of past and projected climate change information. The report deviates from the previous assessment’s method in its approach to representing robustness and uncertainty in maps, based on new research on visualizing uncertainty and user surveys. The report covers various topical sections, including large-scale climate changes, understanding the climate system’s response, and regional climate changes. Information is presented in a structured manner, with summaries at the beginning of each section and clear data tables for every chapter, in the spirit of the Findable, Accessible, Interoperable, and Reusable (FAIR) principles for scientific data. – AI-generated abstract.