How much climate change is there in the current heat wave that is weighing on Europe and Germany these days? Weather experts are divided: On the one hand, they always emphasize that there were often very hot days in June, i.e. in early summer. And above all: that such heat waves lasting a few days are “weather” – and not “climate change”.
On the other hand, Clare Nullis, spokeswoman for the World Weather Organization (WMO) in Geneva, under the impression of the current heat wave, emphasizes: The extremely high temperatures that have spread from North Africa to southern Europe and reached Switzerland and Germany this weekend are rather typical for July or August – and not for June.
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Due to climate change, such extreme weather conditions would occur more frequently in the future as unusually early and intensely as they do in Europe, says Nullis, according to dpa. “Unfortunately, what we are experiencing today is a foretaste of the future.” This is due to the high concentrations of gases in the atmosphere that cause the greenhouse effect.
In some parts of Spain and France, thermometers have climbed more than ten degrees above the mean for this time of year, reports Nullis. Spain, Portugal, Hungary and Serbia are affected by drought.
As reported last year, data from the German Weather Service (DWD) showed that climate change is now having a strong influence on the weather in Germany – in some cases even to a greater extent than worldwide. A fact paper by the DWD showed that the past decade was up to two degrees warmer than the first decades of weather observations from 1881 to 1910.
Overall, the average temperature in Germany has risen by 1.6 degrees since 1881 – worldwide this value is 1.1 degrees lower. The frequency of extreme heat waves has demonstrably increased, while severe frosts have decreased, according to the DWD: “Long-lasting phases with daily maximum temperatures of 30 degrees and above are a new phenomenon in some areas.”
Exactly one year ago, the weather conditions in Germany had led to “hot” days with maximum temperatures of over 30 degrees Celsius and “tropical nights” almost everywhere. According to meteorological definitions, these are days with temperatures above 30 degrees and nights when the temperature does not fall below 20 degrees Celsius.
Weather researchers speak of a “heat wave” when the average maximum temperature exceeds 30 degrees Celsius over a period of at least five consecutive days. This mark is currently likely to be missed because at least for Berlin and Brandenburg on Monday a drop in temperature to around 19/20 degrees is predicted. But then a gradual rise to 31 degrees should follow on Friday.
On the question of the extent to which heat waves are evidence of climate change, the DWD takes the position that climate changes only become apparent when the long-term average values of a more recent period are compared with those of older periods. The average temperature in Germany, which is 1.6 degrees higher than in 1881, actually contributes to the fact that the limit values are exceeded more frequently, there are more hot days and more heat waves.
The intensity and duration of heat waves have increased over the past 30 years, which is why Andreas Friedrich from the DWD also found out. “Heat waves have become much more likely due to warming.”
This trend can be observed worldwide, not only in Germany and Europe. However, the number of heat waves in Western Europe has “increased more than one would expect in the past two decades,” said Dim Coumou, who researches climate extremes at the VU Amsterdam and for the Dutch weather service KNMI, the Tagesspiegel on the occasion of the heat wave a year ago.
Two theories are discussed in climate research as explanations beyond the greenhouse effect. On the one hand, the circulation of air currents in the atmosphere has changed. The jet stream that used to cool Europe has weakened, causing heat waves to last longer across the continent.