AR6 WGI Climate Change 2021 Report

Towards urgent global climate change action: Release of IPCC’s latest report « AR6 Climate Change 2021: the Physical Science Basis »

On 9 August 2021, the International Panel on Climate Change (IPCC) released the Working Group 1 contribution to the Sixth Assessment Report (AR6) – “Climate Change 2021: The Physical Science Basis. One of the eight reports making up the IPCC AR6, the Working Group I (WG I) report addresses the most updated physical understanding of the climate system and climate change. With contributions from 234 scientists from organisations in 65 countries, including Mercator Ocean International (MOi), and rigorous reviews by governments and experts, the report brings together the latest advances in climate science. It combines extensive evidence from paleoclimate information, observations, process understanding, climate model simulations. It assesses how and why climate has changed to date, and the improved understanding of human influence on a wider range of climate characteristics, including extreme events. The report comes at a crucial time up ahead of the COP26 session at the UN Climate Change Conference set to take place in November 2021, and provides the evidence and information to support the urgent need for increased international commitment and global action on climate change.

Authoritative, comprehensive, accurate and regular information on marine environments in the face of climate change is more than ever needed for informed decision-making and urgent climate action. Mercator Ocean International, a trusted provider of ocean expertise and information, is fully committed to strengthening the science-policy interface, and increasing public awareness and engagement in actions in support of a sustainable ocean. We monitor and provide crucial information on the changing state of the ocean.  From increased ocean acidification to ocean warming and sea level rise, our work shows that these indicators are all increasing unprecedented due to climate change. These alarming trends are real and backed up by scientific evidence, and it is our role to get this information out there to policy and decision makers, and the wider public by contributing to key inputs, such as the IPCC assessment reports for the international negotiations on climate change. – Pierre Bahurel, CEO of Mercator Ocean International

MOi’s contribution to understanding the Ocean-Climate Nexus

The changing state of the global ocean is a recurring theme in the entire WG I Climate Change 2021 Report, which addresses several ocean topics.

>>Show Ocean Topics in AR6 Climate Change 2021: The Physical Science Basis
  • Large-scale indicators of observed change in the ocean (chapter 2)
  • Human influence driving ocean change (chapter 3)
    future projected changes in the ocean in the 21st century and beyond, and implications of climate policy (chapter 4)
  • Changes of the ocean as critical component of the global carbon cycle and other biogeochemical cycles (chapter 5)
  • Oceanic emissions of marine short-lived Climate Forcers (SLCFs, e.g. aerosols and chemically reactive gases) and climate response of SLCF mitigation (e.g. for shipping) (chapter 6)
  • Changes of the ocean as critical component of the global energy cycle, and for climate feedbacks and climate sensitivity (chapter 7)
  • Changes of the ocean as critical component of the global water cycle (chapter 8)
    past and projected future changes in the ocean, and also particularly for sea level (chapter 9)
  • The relation of global scale to regional scale ocean change under the aspect of the global coupled atmosphere-ocean-land-cryosphere system (Chapter 10)
  • Changes of extreme events such as for example Marine Heat Waves, or El Niño Southern Oscillation (Chapter 11)
  • Ocean changes for regional impact and risk assessment, including information on services such as for example provided by the Copernicus programme (Chapter 12)
  • observed and projected changes in ocean-related climate indicators across several regions, also available as interactive tool on the IPCC webpage (Chapter Atlas)


The report uses Ocean Monitoring Indicators from the Copernicus Marine Service, which is implemented by MOi, particularly on global ocean heat content and ocean acidification. It also relies on information from Copernicus Marine’s Ocean State Report, a European reference report published annually by MOi, which provides a comprehensive and state-of-the-art assessment of the global ocean and European regional seas.

We have known for decades that the world is warming. Recent changes in the climate are widespread, rapid, and intensifying, and are reaching levels and rates unseen in centuries to many thousands of years. In the ocean for example, the rate of sea level rise is faster over the last hundred years than at any time in at least the last 3000 years. The global ocean has warmed faster over the past century than since the end of the last deglacial transition (around 11,000 years ago). Acidification of the open surface ocean as high as recent decades is unusual in the last 2 million years. Human influence is the main driver of these changes in the ocean set in motion by climate change. These ocean changes are slow processes, which are irreversible for hundreds to thousands of years, and will thus continue – but these changes would be slower with lower emissions. – Dr. Karina von Schuckmann, Ocean Climate Monitoring expert, Mercator Ocean International

MOi’s contribution to the IPCC AR6 is provided by Dr. Karina von Schuckmann, an oceanographer specialised in ocean climate monitoring, who also heads the publication of the Ocean State Report and Ocean Indicator activities. Von Schuckmann is a lead author of the IPCC AR6 WG I main report of Chapter 2 assessing the observed changing state of the climate system, and its technical summary. She is also a contributing author to other parts of the report including the Summary for Policy Makers, a key document providing key insights of the WG I full report, intended for government leaders. She has also participated in the scoping meeting of the AR6 Synthesis Report.

In September 2019, the IPCC released the cross-cutting working group Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC). Among the set of reports of the IPCC’s 6th assessment cycle, the SROCC report also draws on the expertise of MOi, under the guidance of von Schuckmann – a Lead Author of Chapter 1 of the report,  and uses knowledge of the ocean from the Copernicus Marine Service.

About the IPCC 6th Climate Change Assessment Cycle

The IPCC Sixth Assessment Cycle comprises eight reports released over the period 2015 to 2023, providing the latest scientific basis to inform climate change policies and the United Nations Sustainable Development Goals. A total of five reports have been released to date with the most recent being the AR6 WG I report (Climate Change 2021: Physical Science Basis). The cycle culminates in a final synthesis report that builds on the findings from all three working group reports and three cross-Working Group Special Reports. The 6th assessment cycle is the most ambitious so far, with the work schedule readjusted with the COVID-19 pandemic and drawing in even more participation by experts from all over the world. MOi is fully committed to strengthening international ocean governance and policy coherence for a sustainable ocean , and will continue to lend its ocean expertise to the IPCC in preparing its latest assessment reports for better informed national policy making, global climate negotiations and ultimately urgent global climate action.

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