Geneva (dpa) – How the climate is changing and that humans are responsible for it has been described by the Intergovernmental Panel on Climate Change (IPCC) since its first report in 1990.
The forecasts of a sharp temperature rise and devastating consequences have always scared you. But then there was a long pause: from 1998 to 2014, the global average temperature hardly changed. The scientists are scratching their heads.
“Not that anyone had any doubts about the base,” says Jochem Marotzke of the Max Planck Institute for Meteorology in Hamburg of the German Press Agency. “But you wonder when such a phenomenon occurs that you did not foresee: where are the limits of our knowledge?” Climate skeptics were already jubilant, but then it turned out to be very big.
As soon as the 5th IPCC Assessment Report 2013/2014 came out, the global mean temperature rose dramatically. The past six years – 2015 to 2020 – have been the warmest since records began. 2016, 2019 and 2020 were the three warmest years with minimal differences. That little happened between 1998 and 2014 was a normal fluctuation, but statistically an extreme event, says Marotzke, “like throwing a 6 eight times in a row for “Mensch ärgere Dich nicht”.
The long-awaited first part of the new status report, which deals with the scientific basis of climate change, will be published on August 9. It will finalize at a two-week IPCC meeting on July 26. One thing is clear in advance: the new report will be different.
“The focus has shifted,” said Douglas Maraun, a German co-author and statistical modeling expert at the University of Graz in Austria of the dpa. “In the past, the main question was, ‘What is the human contribution to climate change?’ That question has been answered. Now it is moving more in the direction of climate risks. Now you need a report as a basis for adjustments.” This includes, for example, the best possible predictions for regional climate change.
That’s why the new report includes an interactive regional atlas for the first time. There you can see what regional effects certain climate indicators can have at certain times of the year, as Maraun says. This cannot be broken down to the national level, but to regions, such as Central Western Europe, including Germany.
“Summer temperatures here are rising much more than simulated by climate models,” Maraun says. “Research is underway on the role that aerosols and natural fluctuations play in this.”
Aerosols, which are created by volcanic eruptions or desert storms, but also by the burning of fossil fuels, usually have a cooling effect and counteract greenhouse gases. Improvements in air quality since the 1970s may have partially eliminated this effect.
For various reasons, climate change in Germany is even more noticeable than the average on Earth. According to co-author Astrid Kiendler-Scharr of Forschungszentrum Jülich, global temperatures have risen by an average of about 1.1 degrees above pre-industrial levels since 1881 and in Germany by about 1.6 degrees.
Other key figures for Germany: Sunshine duration: plus 17 percent since 1981, number of warm 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.
A climate model of the effects of Mediterranean warming predicted more heavy rain in 2016, just ahead of the German region that recently experienced the flood disaster, said ocean researcher Mojib Latif of the Geomar Helmholtz Center for Ocean Research in Kiel. “People are just leaving the climate comfort zone, now it’s getting dangerous,” he said.
Sea level rise will also be a big topic, says Marotzke, also a co-author. “This question is hotly debated in science.” The biggest uncertainty factors are the large ice sheets of Greenland and Antarctica and their possible instabilities.
What has happened since the last message? “I can’t think of anything spontaneous where things were less dramatic than the models predicted,” Maraun says. Still, he was “slightly optimistic”: “Climate protection policies are making a difference, we are far from green, but the very dystopian is becoming less likely.” The goal of the Paris climate agreement to stay below 1.5 degrees if possible is “sporty”. He even describes them as optimists who assume a temperature of three degrees Celsius.
According to Maraun, a challenge is to shape climate protection in harmony with the biosphere. “If you grow rapeseed and energy forests everywhere, you may have protected the climate, but you’re destroying biodiversity,” he says.
Marotzke argues with activists who create atmosphere with doomsday scenarios: “I struggle with the concept of ‘point of no return’, the point at which the effects of climate change are irreversible. Of course, we will irrevocably lose some things, such as coral reefs. But when the disaster poetry is sung, it sounds like that point will come and then the world will end no matter what we do,” he says. “There is no such point. It is always worthwhile to prevent or limit further warming.”