IPCC Working Group I report on the Physical Science Basis of Climate Change 2021


By Jasmin Kemper

20 August 2021

The IPCC has finalized the first part of the Sixth Assessment Report (AR6), ‘Climate Change 2021: The Physical Science Basis’, the Working Group I (WGI) contribution to AR6. It was finalized on 6th August 2021 during the 14th Session of Working Group I and 54th Session of the IPCC.

This report from IPCC’s WGI is their update on the science of climate change. It includes new evidence from climate science, and re-emphasises why we need to reduce emissions quickly, and why CCS is needed for permanent CO2 removal (CDR). It is very comprehensive in its 3949 pages, covering the current state of the climate, the future climate, risk and adaptation, and limiting future climate change. It explores why and how CDR is needed to compensate for residual emissions in order to reach net-zero. A sobering conclusion is that even with achieving sustained net-zero emissions, while there would be limits to temperature increases and gradual reversals of atmospheric CO2 and surface ocean acidification, other climate changes already in the global systems would continue for decades and more. The WGI report draws heavily from the findings of the recent Special Reports: SR1.5, SRCCL, and SROCC.

IEAGHG’s main input is to IPCC’s WGIII (Mitigation) but it is good to see our work also used in this WGI report (an IEAGHG paper from GHGT-12 in 2014 on the London Protocol).

In conclusion, the WGI report underlines the importance of CDR for reaching climate targets, both in terms of 1.5/2°C and net-zero/net-negative pathways but also reminds of the temporal aspects, i.e. the response of the climate system will be delayed. It also highlights regional approaches will be required due to the different benefits and trade-off of each CDR method.

It is also worth mentioning that the tables presenting the sequestration potential of the different CDR options have the caveat that for some potential estimates (e.g. BECCS, A/R, SOCS, biochar) environmental and social factors were considered, whereas for others (e.g. DACCS, enhanced weathering) they were not. The latter are areas where IEAGHG could contribute with future studies, as we are currently carrying out a study with Element Energy on DACCS, which will be published later this year.

The WGI report ‘Climate Change 2021: The Physical Science Basis’ is available on the IPCC’s website:


A more detailed description of the CDR related key messages can be found in the following IEAGHG Information Paper (IP):

2021-IP14 IPCC Working Group I report on the Physical Science Basis of Climate Change 2021

Jasmin Kemper & Tim Dixon

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