With no other topic are climate researchers so sure about the future trend as with temperature and heat.
When it comes to precipitation, there is a lot to be said for more extremes. But the models are uncertain on this point, especially for Central Europe, says Jakob Zscheischler from the Helmholtz Center for Environmental Research in Leipzig. “When it’s hot, it’s clear that things will continue as they have in recent years.” In all models it gets warmer, in some even extremely hot.
“40 degrees in Germany are becoming the norm,” explains Peter Hoffmann from the Potsdam Institute for Climate Impact Research. “Today’s extreme years with 20 hot days will become average summers by the end of the century if we don’t take massive countermeasures in the coming years.”
Range of climate scenarios
The projections of the climate models for the future always have a certain range. As a rule, a distinction is made between two extreme scenarios: if everything continues as before in terms of climate protection (the so-called emissions scenario RCP8.5) and if the global projects are implemented consistently (RCP2.6).
For this purpose, a network of experts from the Federal Ministry of Transport has calculated specific figures with experts from the German Weather Service (DWD), among others: According to this, the 30-year average temperature in the summer months in Germany in the period 2071 to 2100 could be three to five degrees higher than in the comparable period of 1971 by 2000. As a result, daily highs of over 45 degrees would be reached at least as often as is currently the case for the 40-degree mark.
According to this data, the number of hot days with 30 degrees and more could most likely be in a range of 9.4 to 23.0 per year on average across Germany. For comparison: From 1971 to 2000 there were only 4.6 such days on average nationwide. The number of summer days with maximum temperatures of 25 degrees or more could even rise to 39.5 to 63.8 (comparative period: 29.0). On tropical nights when the thermometer shows no less than 20 degrees, 0.8 to 7.8 degrees per year are possible. In the comparative period from 1971 to 2000, the value was 0.1. The nationwide average values ??also mean that regions can deviate significantly from this.
Current climate path looks bad
According to Andreas Becker, head of the DWD climate monitoring department, current measurements clearly indicate that Germany and the world are still moving along the path of the worst scenario (RCP8.5). This does not include the climate protection projects. Nevertheless, it is important to consider the other scenarios. “Even if we’re just starting with climate protection today, we can still exert influence,” he explains. “Every tenth of a degree counts.”
Becker also emphasizes the generational conflict in climate protection: Depending on the climate protection efforts, many of today’s decision-makers are predicted to warm by the end of their life expectancy around 2050 in a range of 1.1 to 1.4 degrees (compared to 1971 to 2000). “That’s a difference of 0.3 degrees. That also makes a big difference.” By the end of the century, depending on climate protection measures, it could be 1.1 to 3.8 degrees more.
This means that the difference between successful and unsuccessful climate protection for children and grandchildren is 2.7 degrees. The latter has “dramatic consequences, some of which are not yet foreseeable,” Becker makes clear. “The costs of our adaptation to climate change of this magnitude would far exceed the costs of current, ambitious climate protection and would even come up against the limits of feasibility.”
Autumn in particular will probably be warmer
With all the average values, there can of course be even clearer regional swings, as Zscheischler explains. The expected development for the seasons is also different. A climate impact and risk analysis for Germany by the Federal Environment Agency assumes that the temperature rise in autumn is significantly greater than in spring.
Climate researcher Andreas Fink from the Karlsruhe Institute of Technology is working with colleagues as part of the ClimXtreme network on approaches for better preparation for extremes and on the question of how to better project very extreme heat waves. “In the end, it will not be the changes in the monthly averages or the average number of hot days, but heat waves of extreme intensity, duration and extent that will cause the greatest “damage”.
Hoffmann from the Potsdam Institute for Climate Impact Research assumes that there will also be heat waves and phases of slight cooling in the future. However, changes in air flow could lead to extreme weather conditions stabilizing for a longer period of time. The jet stream is slowing down and with it the westerly wind circulation, explains the expert. This could lead to air masses flowing from one direction to Central Europe for longer. The first days of summer can then be the beginning of a long-lasting heat wave – or the hoped-for rain can be the trigger for flooding.
“Then heat waves can become really dangerous,” warns Hoffmann. “40 degrees over several days like in the Mediterranean region are too much for our usual conditions.” In nature, you can already see the consequences of milder winters, warm springs and hot, dry summers. The researcher warns that prolonged periods of heat are also a danger to human health. This has consequences for productivity: “Heat waves don’t always have to fall on vacation.”
