The Intergovernmental Panel on Climate Change (IPCC) has been describing how the climate changes and that humans are responsible for it since its first report in 1990. The prognoses with a sharp rise in temperature and devastating consequences have always made one fearful and anxious. But then there was a long pause: from 1998 to 2014, the global mean temperature hardly changed. The scientists scratch their heads.
Exultant climate change skeptics – then it turned out to be very big
“Not that anyone had any doubts about the basics,” says Jochem Marotzke from the Max Planck Institute for Meteorology in Hamburg to the German Press Agency. “But one wonders when such a phenomenon occurs that one had not foreseen: where are the limits of our knowledge?” Climate change skeptics were already exulting, but then it turned out to be very big.
As soon as the 5th IPCC Assessment Report 2013/2014 was out, the global mean temperature rose dramatically. The past six years – 2015 to 2020 – were the warmest since measurements began. 2016, 2019 and 2020 were the three hottest years with minimal differences. The fact that little happened between 1998 and 2014 was a normal fluctuation, but statistically an extreme event, says Marotzke, “as if you rolled a 6 eight times in a row for” Mensch ärgere Dich nicht “.
On August 9th, the eagerly awaited first volume of the new status report will be published, which deals with the scientific basis of climate change. It will get the finishing touches in a two-week IPCC meeting from July 26th. One thing is clear in advance: the new report will be different.
“The focus has shifted,” says Douglas Maraun, a German co-author and expert on statistical modeling at the University of Graz in Austria of the dpa. “The main question used to be:” What is the human contribution to climate change? “This question has now been answered. Now it is more in the direction of climate risks. Now you need a report as a basis for adaptation.” This includes, for example, the best possible forecasts for regional climate change.
“Summer temperatures rise faster than simulated by climate models”
That is why the new report contains an interactive regional atlas for the first time. There you can see what regional effects certain climate indicators are likely to have at certain times of the year, as Maraun says. This cannot be broken down to the state level, but to regions, such as Central-Western Europe, which includes Germany.
“Summer temperatures rise here much more than simulated by climate models,” says Maraun. “Research is being carried out into the role that aerosols and natural fluctuations play in this.”
Germany is above average
Aerosols, which arise from volcanic eruptions or desert storms, but also the combustion of fossil fuels, usually have a cooling effect and counteract greenhouse gases. The improvement in air quality since the 1970s may have partially eliminated this effect.
In fact, for various reasons, climate change is more noticeable in Germany than on average on earth. Worldwide, the temperature has risen by an average of around 1.1 degrees above pre-industrial levels, and in Germany by around 1.6 degrees since 1881, as co-author Astrid Kiendler-Scharr from Forschungszentrum Jülich says.
Other key figures for Germany: Sunshine duration: plus 17 percent since 1981, number of hot days: plus 196 percent since 1951, number of days with heavy rain: plus five percent since 1951, sea level: plus 42 centimeters in Cuxhaven since 1843.
More heavy rain was predicted in 2016
In a climate model of the consequences of the warming of the Mediterranean, more heavy rain was predicted in 2016 precisely for the German region that recently experienced the flood disaster, said ocean researcher Mojib Latif from the Geomar Helmholtz Center for Ocean Research in Kiel. “People are just leaving the climatic comfort zone, now it’s getting dangerous,” he said.
The rise in sea levels will also be a big topic, says Marotzke, also co-author. “This question is hotly debated in science.” The greatest uncertainty factors are the large ice sheets of Greenland and Antarctica and their possible instabilities.