As low Lambert reached western Germany on Thursday afternoon, the maps of lightning detection services on the Internet suddenly lit up: the discharges in the atmosphere in Rhineland-Palatinate and North Rhine-Westphalia could be tracked almost every second. Lightning and thunder were accompanied by heavy rain and hurricanes, which spread across large parts of Germany by the evening.
In view of such a dangerous weather situation, one might think that Central Europe is particularly affected by thunderstorms. From a global perspective, however, this is not the case: Lake Maracaibo in Venezuela currently holds the lightning record, where there is an average of 297 days of thunderstorms per year. Most of the other lightning hotspots are also found in the tropics, especially in Africa, where the muggy, warm weather favors the formation of thunderstorms.
However, global warming is probably causing more thunderstorms to brew even in temperate latitudes than a few decades ago. A team of atmospheric scientists and statisticians from the University of Innsbruck has just shown this for the eastern Alpine region. Like the researchers in the journal Climate Dynamics to reportlightning activity in the high Alps has roughly doubled in recent years compared to the 1980s.
Especially in June – generally the month with the strongest risk of thunderstorms – the probability of getting caught in a storm while hiking in the Alps has increased significantly. At the same time, the thunderstorm season, which typically runs from May to September, has lengthened somewhat. “It starts earlier and ends later,” says statistician Thorsten Simon from the University of Innsbruck, the first author of the study. This also applies to the course of the day: the likelihood of thunderstorms now begins earlier in the afternoon and subsides later at night than it did a few decades ago.
The High Alps are rising faster than the rest of Europe
According to the scientists, the changes are more pronounced in high Alpine locations, especially around the main Alpine ridge. North of the Alps, in the foothills of the Alps and in the Bohemian Forest, the trend is much weaker. These local differences could be related to climate change. “We know that the high Alps are warming up much faster than the rest of Europe,” says Simon. The research team therefore assumes that the rise in temperatures in particular explains the increase in the risk of thunderstorms at higher altitudes.
Even if the scientists emphasize that these are “indications” – the observations fit the picture: US researchers were able to prove some time ago that there are now around a quarter of a million thunderbolts a year in the Arctic, for example seven times as often as in 2010. The researchers suspect warmer summers in the far north, triggered by climate change, to be the cause. In Siberia, the higher risk of thunderstorms poses a risk to forests, since lightning strikes can cause fires.
In the Alps, increasing lightning activity could also increase the risk of forest fires, Simon suspects. This is not the only reason why hikers should always keep an eye on the weather. Thunderstorm cells form faster on the steep slopes of the Alps than elsewhere – and since they are often localized, their prediction is also particularly difficult.