“36 degrees, and it’s getting hotter” sang the band 2Raumwohnung in 2007. A hunch? A few heat waves later it becomes clear what we have to prepare for.
With no other subject are climate researchers so sure of the future trend as with temperature and heat.
When it comes to precipitation, there is much to be said for more extremes. But the models are uncertain at this point, especially for Central Europe, says Jakob Zscheischler of the Helmholtz Center for Environmental Research in Leipzig. “When it’s warm, it’s clear it will continue as it has for the past few years.” It gets warmer in all models, in some even extremely hot.
“40 degrees in Germany is becoming the norm,” explains Peter Hoffmann of 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 scope. As a rule, a distinction is made between two extreme scenarios: if everything in the field of climate protection continues (the so-called emission scenario RCP8.5) and if the global projects are carried out consistently (RCP2.6).
For this purpose, a network of experts from the Federal Ministry of Transport has calculated specific figures with experts from, among others, the German Weather Service (DWD): according to these, the 30-year average temperature in the summer months in Germany in the period 2071 to 2100 would be in 2000 could be three to five degrees higher than in the comparable period of 1971. As a result, daytime temperatures above 45 degrees would be reached at least as often as is the case for the 40-degree mark today.
According to this data, the number of warm days with 30 degrees and more in all of Germany could probably be between 9.4 and 23.0 per year. In comparison, from 1971 to 2000 there were only 4.6 such days nationwide. The number of summer days with maximum temperatures of 25 degrees or more can even rise to 39.5 to 63.8 (comparison period: 29.0). On tropical nights when the thermometer reads a whopping 20 degrees, 0.8 to 7.8 degrees per year is possible. In the comparative period from 1971 to 2000, the value was 0.1. Regions can also deviate considerably from the national average values.
Current climate path looks bad
According to Andreas Becker, head of DWD’s climate monitoring division, current measurements clearly indicate that Germany and the world are still on the worst-case path (RCP8.5). This does not include climate protection projects. However, it is important to take the other scenarios into account. “Even if we are just starting climate protection today, we can still make an impact,” he explains. “Every tenth degree counts.”
Becker also emphasizes the generational conflict in climate protection: depending on climate protection efforts, many of today’s decision-makers are forecasting a global warming of 1.1 to 1.4 degrees by the end of their life expectancy around 2050 (compared to 2050). 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 failed climate protection for children and grandchildren is 2.7 degrees. The latter has “dramatic consequences, some of which cannot yet be foreseen”, Becker explains. “The costs of our adaptation to climate change of this magnitude would far exceed the costs of today’s ambitious climate protections and would even be approaching the limits of its feasibility.”
Autumn is especially likely to get warmer
Of course, with all the mean values there can be even more pronounced regional fluctuations, Zscheischler explains. The expected development for the seasons is also different. A climate impact and risk analysis for Germany by the Federal Environment Service assumes that the temperature increase in autumn is significantly greater than in spring.
Climate researcher Andreas Fink of the Karlsruhe Institute of Technology is working with colleagues as part of the ClimXtreme network on approaches to better prepare for extremes and how to better project very extreme heat waves. “Ultimately, it is not the changes in the monthly averages or the average number of warm days, but heat waves of extreme intensity, duration and magnitude that will cause the greatest ‘damage’.”
Hoffmann of the Potsdam Institute for Climate Impact Research assumes that there will also be heat waves and phases of mild cooling in the future. However, changes in airflow can cause extreme weather events to stabilize for an extended period of time. The jet stream slows down and with it the westerly wind circulation, the expert explains. This can cause air masses to flow longer from one direction to Central Europe. The first days of summer can then be the start of a prolonged heat wave – or the expected rain can be the cause of flooding.
“Then heat waves can become really dangerous,” warns Hoffmann. “40 degrees over several days, like in the Mediterranean, is 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 heat also poses a threat to human health. This affects productivity: “Heat waves don’t always have to fall on vacation.”