IPCC AR6

IPCC AR6, the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, is the most recent comprehensive synthesis of climate‑science research, impact assessments, and mitigation pathways. Published in three volumes between August 2021 and April 2022, with a Synthesis Report released in March 2023, it provides the authoritative benchmark for the global community’s understanding of how far the climate system has already changed and what is required to limit warming to 1.5 °C or 2 °C. Its significance lies in the unprecedented granularity of its data, the integration of the latest Earth‑system models, and the direct linkage of scientific findings to the policy frameworks that guide the Paris Agreement and subsequent COP negotiations. ## Origins and Development The IPCC was established in 1988 by the United Nations Environment Programme and the World Meteorological Organization to assess scientific, technical and socio‑economic information relevant to climate change. Its assessment cycle, originally set at roughly every five to seven years, has produced five prior reports, each expanding the scope and depth of analysis; AR6 follows the Special Report on Global Warming of 1.5 °C (2018) and the Fifth Assessment Report (2013‑2014). The AR6 drafting process began in 2019, engaging 2345 authors, reviewers and contributors from 91 countries, and was overseen by a steering committee chaired by Hoesung Lee (South Korea) and supported by 30 governments that provided funding and logistical support. The multi‑year timeline culminated in the release of Working Group I (The Physical Science Basis) on 9 August 2021, Working Group II (Impacts, Adaptation and Vulnerability) on 28 February 2022, and Working Group III (Mitigation) on 4 April 2022, followed by the Synthesis Report on 20 March 2023. ## Structure and Methodology AR6 is organized around three Working Groups, each producing a standalone volume that is peer‑reviewed through a multi‑stage process involving at least two rounds of expert and government review. Working Group I relied on the Coupled Model Intercomparison Project Phase 6 (CMIP6) ensemble, encompassing 27 climate models and over 400 simulations, to quantify the observed warming of 1.1 °C above pre‑industrial levels as of 2022. The report adopts the Shared Socio‑Economic Pathways (SSPs) framework, ranging from SSP1‑1.9 (a rapid‑decarbonisation scenario) to SSP5‑8.5 (high‑fossil‑fuel use), to explore how socioeconomic trajectories intersect with emission pathways. Confidence language—“very high,” “high,” “medium,” and “low”—is applied consistently across all chapters, allowing policymakers to gauge the robustness of each finding. ## Key Scientific Findings The Physical Science Basis volume confirms that each of the last four decades has been successively warmer than any preceding decade since 1850, with 2023 ranking among the warmest years on record. Extreme heat events have become five to six times more likely in many mid‑latitude regions, while the global mean sea level is projected to rise between 0.28 m and 0.55 m by 2100 under the intermediate SSP2‑4.5 scenario. Working Group II highlights that climate‑related mortality increased by 20 % between 1990 and 2019, and that food‑security risks are now acute for more than 3 billion people living in low‑latitude zones. Working Group III quantifies that limiting warming to 1.5 °C requires a cumulative CO₂ budget of roughly 500 GtCO₂ from 2020 onward, translating to a 45 % reduction in global CO₂ emissions by 2030 and net‑zero emissions by around 2050. The report also stresses that achieving these targets demands a rapid transition in energy, industry, transport, and land‑use sectors, with renewable electricity needing to supply 70 %–85 % of global power by 2050. ## Policy Relevance and Global Impact AR6’s findings have been central to the United Nations Framework Convention on Climate Change (UNFCCC) deliberations, informing the updated Nationally Determined Contributions (NDCs) submitted ahead of COP28 in Dubai. The Synthesis Report’s concise policy‑relevant summary is routinely cited by the International Monetary Fund, the World Bank, and major sovereign wealth funds when assessing climate‑aligned investment strategies. Moreover, the report’s carbon‑budget estimates have been adopted by the Global Stocktake mechanism to evaluate collective progress toward the Paris Agreement’s long‑term temperature goals. National governments, from the European Union to Japan, have incorporated AR6 scenarios into their climate‑action plans, often using the SSP pathways to align domestic policies with the “net‑zero by mid‑century” trajectory. ## Current Status and Future Outlook Implementation of AR6