IPCC AR6

The IPCC Sixth Assessment Report (AR6) is the most recent full assessment cycle of the Intergovernmental Panel on Climate Change, the UN body established in 1988 by UNEP and the WMO to provide governments with scientific assessments on climate change. AR6 was produced by three Working Groups plus a Synthesis Report:

• Working Group I (The Physical Science Basis) was released in August 2021. It concluded that it is "unequivocal" that human influence has warmed the atmosphere, ocean, and land, and that global surface temperature had reached roughly 1.1°C above 1850–1900 levels.
• Working Group II (Impacts, Adaptation and Vulnerability) was released in February 2022, emphasizing that roughly 3.3–3.6 billion people live in contexts highly vulnerable to climate change.
• Working Group III (Mitigation of Climate Change) was released in April 2022, assessing pathways consistent with limiting warming to 1.5°C or 2°C and the role of demand-side measures, finance, and technology.
• The AR6 Synthesis Report was approved in Interlaken and released on 20 March 2023.

AR6 introduced five core Shared Socioeconomic Pathways (SSPs) — SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 — used to project warming under different emissions and development assumptions. It also refined the estimate of equilibrium climate sensitivity to a likely range of 2.5–4°C, narrower than in AR5.

For diplomatic practice, AR6 is the scientific reference underpinning negotiations under the UNFCCC and the Paris Agreement, including the first Global Stocktake concluded at COP28 in Dubai in December 2023. Delegates frequently cite AR6 language on the remaining carbon budget, the necessity of deep, rapid, and sustained emissions reductions, and the finding that current Nationally Determined Contributions are insufficient to hold warming to 1.5°C without overshoot.