"This report provides the most complete digest of the understanding of the current state of the climate, including its evolution, the role of the influence of man, the state of knowledge on the possible futures of the climate", indicates in the preamble the Intergovernmental Panel on Climate Change.

It is seven years since the IPCC, placed under a UN mandate, had not done this work of updating scientific knowledge on climate systems and climate change.

This is done on Monday with the publication of a report of several thousand pages, reduced to 42 for its "summary for decision-makers".

This synthesis, which the IPCC produces for each of its publications intended for political leaders, was discussed, line by line, by the 195 member states of the Conferences of the Parties (COP) on climate change over the last fifteen days, before to be approved last Friday.

In other words, the whole observation described in these 42 pages has been approved by the international community.

The foundation for the rest of the evaluation report?

A total of 234 authors from 66 countries participated in the development of this new report. They synthesized over 14,000 scientific studies and responded to 78,000 comments from peers and governments. A long-term work therefore and which constitutes only the first of the three components of the evaluation report that the IPCC is about to publish. Its sixth since its creation in 1988. The other two components? They will follow in February and next March, one on the impacts and adaptations to climate change, the other focused on the solutions to be provided. The final report, covering the three parts, is expected in the fall of 2022.

This first report, published on Monday, therefore launches the movement, by making this major update of scientific knowledge on climate change.

The basis for the rest of the assessment?

"We now have a much clearer picture of the past, present and future climate," explains French climatologist Valérie Masson-Delmotte, co-chair of group 1 of the IPCC.

Which is essential to understand where we are going, what can be done and how we can prepare.

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"Unprecedented changes for centuries or even millennia"

And this first part urges the international community to act against climate change, as the findings are alarming and are drawn up by the authors with a high degree of confidence. "The magnitude of recent changes observed in the climate system has been unprecedented for centuries or even, sometimes, millennia", points out the IPCC.

This is particularly the case for greenhouse gas concentrations in the atmosphere. “In 2019, atmospheric CO2 concentrations were higher than at any other time for at least 2 million years,” illustrate the authors, adding that the current state of climate science allows us to say so with a high degree of confidence. The same goes for the concentrations of methane and nitrous oxide. "In 2019, they were higher than at any other time for at least 800,000 years", indicates the IPCC.

The consequences are being felt. The IPCC lists them, starting with the global surface temperature. This "has increased more rapidly since 1970 than in any other 50-year period over the past 2,000 years." As for the Arctic sea ice, its annual average area over the decade 2011-2020 reached its lowest level since at least 1850 (strong confidence). At the end of last summer, the surface area of ​​the sea ice had never been so low at this time of the year for at least the last 1,000 years, specifies the IPCC (with average confidence). The average rise in sea level is not reassuring either. "It has increased more rapidly since 1900 than in any previous century at least over the last three millennia," continues the IPCC.

An "unequivocal" responsibility of man

This report does not only draw up these observations.

He also looked at the causes of this climate change.

The progress of climate science over the last seven years once again allows the IPCC to take less tweezers.

As a reminder, in its fifth and last assessment report, in 2014, the IPCC spoke of a "clear" influence of human activities on climate change.

"The observed increases in greenhouse gas concentrations since about 1750 are unequivocally caused by human activities," he now writes.

The report estimates that greenhouse gas emissions from human activities have been responsible for about 1.1 ° C of warming since 1850-1900.

The increase in global average precipitation over land since 1950, the salinity of the oceans, the global retreat of glaciers since the 1990s, the decrease in the area of ​​arctic sea ice, the decrease in snow cover in the hemisphere north since 1950, the warming of the upper layer of the oceans (between 0 and 700 meters) ... For all these developments, again, the IPCC considers it very probable that man, through his activities, is the main cause.

Planet

Climate change: Why the next IPCC report, published on Monday, is eagerly awaited

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