Making the 6th IPCC climate assessment report

The UN International Panel on Climate Change (IPCC) assesses the science basis for the ongoing climate changes. In 2017 the IPCC and UN defined the structure of the next climate assessment report (AR6) due to be launched in June 2022. The final report will comprise of three working group contributions on the science basis and a Synthesis report for policy makers to be launched in 2021. The Norwegian lead authors to the IPCC WG1 assessment on the physical climate change sciences. From right:  Sebastian Mernild (The Nansen Center), Bjørn Samset (CICERO), Asgeir Sorteberg (UiBergen), Jana Sillmann (CICERO), Kari Alterskjær (CICERO), Trude Storelvmo (UiOslo), Jan Fulgestvedt (CICERO), Terje Berntsen (UiOslo) and Sebastian Gerland (NP). Credit: CICREO.The Norwegian lead authors to the IPCC WG1 assessment on the physical climate change sciences. From right: Sebastian Mernild (The Nansen Center), Bjørn Samset (CICERO), Asgeir Sorteberg (UiBergen), Jana Sillmann (CICERO), Kari Alterskjær (CICERO), Trude Storelvmo (UiOslo), Jan Fulgestvedt (CICERO), Terje Berntsen (UiOslo) and Sebastian Gerland (NP). Credit: CICREO.This week the lead authors of Working group 1 on the physical science research underpinning the past, present and future climate changes have been gathered in Toulouse in France. More than 250 scientists world-wide contributes to the analysis and writing of the Work Group 1 assessment. Nine Norwegian climate scientists from five institutions contributes to this work, including the director of the Nansen Center Sebastian Mernild.

The IPCC AR6 process is tedious and thorough in order to assure that state of the art scientific knowledge is assessed, included, and that the correct conclusions are made. The Lead Authors of WG1 have meet twice earlier and their first order draft report has during the last six months been available for open review and comments by the world science community. Totally 23.462 comments from 750 scientists have been received, which this week have been discussed, assessed and correctly handled by the lead author team responsible for each of the 12 chapters of the WG1 report. During the meeting in Toulouse the scientists have systematic assess the review comments made to each chapter of the first order report. They have considered new advances in knowledge, consistency within and across the chapters, building on previous assessments and reports, inclusion of input form state of the art climate modelling simulations (CMPI6), a balanced and systematic assessment of available relevant literature and the need to include additional knowledge and expertise.

- Under a strictly directed process the lead authors for each chapter of the WG1 report have been able to make major progresses towards the release of the second order report already due in January next year. Our progress made is according to the overall plan, says Sebastian Mernild from Toulouse.

The Norwegian contributions to the IPCC WG1 team includes participation in the overall WG Bureau (Jan Fulgestvedt, CICERO), Chapter 1: Framing, context, methods (Bjørn Samset, CICERO), Chapter 2: Changing state of the climate system (Sebastian Gerland, NP), Chapter 6: Short-lived climate forcers (Terje Berntsen, UiOslo), Chapter 7: The Earth’s energy budget, climate feedbacks, and climate sensitivity (Trude Storelvmo, UiOslo, Kari Alterskjær, CICERO), Chapter 11:Weather and climate extreme events in a changing climate (Asgeir Sorteberg, UiBergen), Chapter 12:Climate change information for regional impact and for risk assessment (Jana Sillmann, CICERO) and the Regional Atlases (Sebastian Mernild, The Nansen Center).

The scientific topics assessed by WG1 include: greenhouse gases and aerosols in the atmosphere; temperature changes in the air, land and ocean; the hydrological cycle and changing precipitation (rain and snow) patterns; extreme weather; glaciers and ice sheets; oceans and sea level; biogeochemistry and the carbon cycle; and climate sensitivity. The WGI assessment combines observations, palaeoclimate, process studies, theory and modelling into a complete picture of the climate system and how it is changing, including the attribution (or causes) of change. The WG1 assessment provides scientific information relevant for the global community to meet the challenge of climate change. As well as the global scale, WGI looks at variability and changes happening at a regional level, which is closely tied to how impacts and risks to human and natural systems are changing over time. Other important policy dimensions of WGI are the assessment of the amount of carbon emissions compatible with climate and energy targets; interactions between land and the climate; and links between climate and air quality.

The second order report will be completed in January 2020 and made openly available for comments before a similar assessment process addressing the review comments will be completed during next summer. The WG1 report and contributions to AR6 will be finalized in 2021.

In addition to WG1, the IPCC Working Group 2 deals with Climate Change Impacts, Adaptation and Vulnerability and Working Group 3 with Mitigation of Climate Change. The AR6 Synthesis Report will integrate and synthesize the contributions from the three Working Groups that will be rolled out in 2021 into a concise document suitable for policymakers and other stakeholders. The IPCC AR6 assessment will be finalized in the first half of 2022 in time for the first global stocktake under the Paris Agreement.

Sources and more information are available here at IPCC WG1 web and Third Lead Author Meeting.

The lead austhors of the IPCC Working group on the physical science research underpinning the past, present and future climate changes gathered at MeteoFrance in Toulouse in August 2019. Credit: MeteoFrance/IPCC.The lead austhors of the IPCC Working group on the physical science research underpinning the past, present and future climate changes gathered at MeteoFrance in Toulouse in August 2019. Credit: MeteoFrance/IPCC.