The Intergovernmental Panel on Climate Change (IPCC) opened a meeting on 26 July to approve its next report on the physical science basis of climate change, the first part of the Sixth Assessment Report.
The report, prepared by IPCC Working Group I, will provide the most up-to-date physical understanding of the climate system and climate change, bringing together the latest advances in climate science and multiple lines of evidence.
The meeting is being held remotely, the first time the IPCC has conducted an approval session in this format, from 26 July to 6 August 2021, because of the impact of the COVID-19 pandemic. Subject to the decisions of the Panel, the report will be released on 9 August.
“This report has been prepared in exceptional circumstances, and this is an unprecedented IPCC approval session,” IPCC Chair Hoesung Lee told the opening session of the meeting.
Lee thanked the 234 report authors for their commitment and determination to produce the report in the conditions of the pandemic.
“This work has required multiple series of virtual meetings across time zones, disrupting daily lives and work rhythms, especially in the most critical phase of the last 16 months as we shaped the final draft,” he said.
The report, Climate Change 2021: the Physical Science Basis, will provide the latest knowledge on past warming and future warming projections, showing how and why the climate has changed to date, and including an improved understanding of human influence on the climate including extreme events.
There will be a greater focus on regional information that can be used for climate risk assessments.
WMO Secretary-General Prof. Petteri Taalas said that the forthcoming report was critical to the outcome of the United Nations climate change negotiations in Glasgow in November. Political interest is high, but the challenge lies in implementing the Paris Agreement and cutting greenhouse gas emissions, he said.
“Climate change is already very visible. We don’t have to tell people that it exists,” Prof Taalas told the opening session. “We are seeing more extreme events. Heatwaves, drought and the flooding events in Europe and China,” he said. “Massive heating” in the Arctic is affecting the atmospheric dynamics in the northern hemisphere, as evidenced by stagnant weather systems and changes in the behaviour of the jet stream, said Prof. Taalas.
UN Climate Change Executive Secretary Patricia Espinosa said that the world is at a “climate crossroads” and that decisions taken this year would determine whether it will be possible to limit global warning to 1.5°C above the pre-industrial era by the end of the century. The world is currently on the opposite track, heading for a 3°C rise, she said.
“We need to change course urgently.”
UNEP Deputy Executive Director Joyce Msuya said the COVID-19 pandemic “is a warning from the planet that much worse lies in store unless we change our ways.”
“We must get on top of this crisis that threatens our collective future,” said Ms Msuya.
The IPCC was established by UNEP and WMO in 1988 to provide political leaders with periodic scientific assessments concerning climate change, its implications and risks, as well as to put forward adaptation and mitigation strategies.
At the meeting, the 14th Session of Working Group I will consider the Summary for Policymakers of the Working Group I contribution to the Sixth Assessment Report for approval in line-by-line scrutiny and the full report for acceptance. The 54th Session of the IPCC will then accept the work of Working Group I, formally accepting the report.
The aim of this process is to ensure that the Summary for Policymakers is accurate, well-balanced and presents the scientific findings of the underlying report clearly.
The approval plenary is the culmination of the rigorous process of drafting and review that IPCC reports undergo. The first-order draft of the Working Group I report received 23,462 review comments from 750 expert reviewers, the second-order draft received 51,387 review comments from governments and 1,279 experts, and the final government distribution of the Summary for Policymakers that ended on 20 June received over 3,000 comments from 47 governments. Over 14,000 scientific papers are referenced in the report.
The remaining parts of the Sixth Assessment Report will be finalized in 2022.