Thorsten Mauritsen. Photo: Krister Junghahn

”The new report summarizes what we know about climate research, based on results from over 14.000 studies. There are many interesting results. The report establishes that the global warming we have seen since the industrialisation started, is completely caused by human activities. There is also considerable progress in the accuracy of the climate predictions and the understanding of sea level rises and extreme events,” says Thorsten Mauritsen.

What does the results of the report imply for the future climate?

“We must expect rising temperatures in the future, which leads to rising sea levels, heat waves, more extreme precipitation and in some areas even more frequent droughts. How large these changes will be, depends entirely on how much carbon dioxide we emit into the atmosphere in the future.”

How do you make your assessments?

"Something relatively new that has been introduced throughout the new report, and which I myself have been involved in developing, is that we weigh together different sources of information, especially observations, in order to arrive at better accuracy and higher reliability. This is in contrast to previous reports, which to a greater extent had to rely primarily on climate models.”

Is there any chance that the results in the report is wrong?

“The short answer is no. There is no longer a justified doubt, if you look at things like the earth is getting warmer due to human actions, the sea levels are rising, or that heat waves are getting warmer. These changes can now be considered as basic physics. In some other areas there is a little more hesitation, and in some of them the research situation is too weak to make statements. In each case, we evaluate how strong the research is and we state uncertainties when these exist.”

graph showing linear relationship between the cumulative Co2 emissions and global warming until 2050
Global surface temperature increase since 1850–1900 (°C) as a function of cumulative CO₂ emissions (GtCO₂). Figure from the Sixth Assessment Report, Climate Change 2021: The Physical Science Basis.

Do you see any possibility that we can reverse the trend?

“In this report, we deal with the physical part of the climate system, not with technical and political solutions. What is clear, however, is that if you reduce carbon dioxide emissions from burning of fossil fuels to zero, the climate will stabilize at a certain global temperature increase, for example 2 or 3 degrees. If we want to reach the 1.5 degree goal, we must immediately, rapidly and globally reduce carbon dioxide emissions and reach zero emissions by 2050. This is much faster than what the world’s governments as a whole currently are planning. Even in the best case, we must expect to exceed 1.5 degrees for a few decades.”

Read more about IPCC’s Sixth Assessment Report on IPCC’s website.

This article was originally published in Swedish on Stockholm University’s website.