The weeks-long heat in April, which hit the south of the Iberian Peninsula and the neighboring North African states after an already disastrous, historic drought, would have been virtually impossible without climate change. According to the international World Weather Attribution (WWA) initiative, global warming has increased the likelihood of such an extreme heat wave in the region by a factor of a hundredfold – and this is even more "extremely cautiously" estimated.
Joachim Müller-Jung
Editor in the feuilleton, responsible for the "Nature and Science" department.
- Follow I follow
The research group is made up of climatologists who use measurement data, statistical methods and climate models to try to establish a causality between climate change and individual weather events.
For some years now, this method, known as attribution research, has been gaining increasing importance in science and politics, not least because the accelerating global warming is causing – or at least helping to cause – more and more extreme weather events and disasters.
Up to 39 degrees in southern Spain
In the case of the April heat wave in southern Spain, which reached extreme temperatures of up to 39 degrees for days for this time of year, as well as the equally overheated Portugal, Algeria and Morocco (up to 41 degrees), the attribution researchers are even more certain than with many other weather extremes studied so far: The extreme heat is the product of climate change and thus the result of greenhouse gas emissions, which are mainly released during the combustion of fossil fuels. It even exceeds the expectations derived from all climate models published so far. "This event is extremely unusual, even in light of the greatly increased probability that has been calculated," writes the research group, in which scientists from the affected region also participated.
Specifically, the three most extreme days between 26 and 28 April were analyzed. However, it is not only the probability of occurrence that global climate change is increasing, but also temperature peaks are becoming more and more of a problem. If the world were 1.2 degrees colder, i.e. at the level before industrialization, and a heat wave had nevertheless occurred, maximum temperatures would have been two degrees lower on average. In the end, this may be a decisive difference for the affected population. Indeed, people in southern Europe and northern Africa were hit by the heat at a critical time of year for farmers.
A study cited by the scientists, which was carried out years ago in Tunis, came to the conclusion that every additional degree of heat beyond 31.5 degrees outside temperature increases the mortality per day in the affected region by two percent.
Of course, there are no actual numbers of victims from the regions between Spain and Algeria currently being investigated. The prospects for the population, however, are not improving. The WWA climatologists have calculated that if global warming of plus two degrees (compared to pre-industrial levels) is reached, maximum temperatures in the region are likely to increase by at least another degree.