The Sixth Assessment Report (AR6) of the United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) is the sixth in a series of reports which assess scientific, technical, and socio-economic information concerning climate change. Three Working Groups (WG) assess

of which the first WGI study has been published in 2021 and the other two are planned for 2022. The final synthesis report is due to be finished by late 2022.

The first of three working groups (WGI) published Climate Change 2021: The Physical Science Basis on 9 August 2021. A total of 234 scientists from 66 countries contributed to this first of three working group reports. The report's authors built on more than 14,000 scientific papers to produce a 3,949 page report, which was then approved by 195 governments. The Summary for Policymakers (SPM) document was drafted by scientists and agreed to line-by-line by the 195 governments in the IPCC during the five days leading up to 6 August 2021.

According to the report, it is only possible to avoid warming of 1.5 °C or 2 °C if massive and immediate cuts in greenhouse gas emissions are made. In a front page story, The Guardian described the report as "its starkest warning yet" of "major inevitable and irreversible climate changes", a theme echoed by many newspapers as well as political leaders and activists around the world.