A very dry spring is usually followed by a long and hot summer. This is shown by the climate data from the last 1000 years.
Because there was very little rain in April and May this year and the temperatures were above average, Christian Pfister, emeritus professor of climate history at the University of Bern, fears that this summer could be as hot and dry as it has been for almost 500 years, to be more precise none since 1540: “Northern Italy was hit hardest then, as it is today, along with eastern France, southern Germany and the Swiss plateau. Many chroniclers followed the drought with concern.”
In 1540 not a drop of rain fell in Alsace for eleven months.
From mid-June to mid-August in 1540, a so-called omega high blocked the passage of disturbances across Central Europe, explains Pfister: “During this period, not a drop of rain fell in Alsace. Temperatures may have climbed above 40 degrees. Cracks of more than 30 centimeters gaped in the floors.”
A dry runaway in a cooling phase
ETH professor and climate researcher Sonia Seneviratne has been studying the factors that lead to heat waves and droughts for years. She thinks it’s still too early to say how the whole summer of 2022 will end, but: “The federal government’s measurements show that we have very dry conditions at the moment. We have such conditions on average every 20 years. It’s very dry but it’s too early to tell how it’s going to develop.” In 1540 it was dry for eleven months.
If it rained little for so long, we would have a much more pronounced impact than 1540.
We’re still a long way from that, emphasizes Seneviratne. But she adds: “If it rained little for so long, we would have much more pronounced effects than in 1540. We have higher temperatures and more radiation in the system. That means we would have even higher temperatures and more drought.”
much higher water consumption
Pfister also believes that we are more vulnerable to climate extremes today than we were 500 years ago: there are around ten times as many people in our country as there were then. “The glaciers used to store water have melted down to a fraction. We are dependent on food and feed imports. Our drinking and process water requirements are many times higher than 1540.”
The authorities urgently need to adjust their scenarios and also take into account the worst-case scenario with a drought period comparable to 1540 in their planning, he emphasizes: “I hope that my fears will not come true. But I assume that due to the ongoing warming, a worst-case event can be expected in the next few years.”
Legend:
The drought is a challenge for agriculture.
key stone
At the same time, the community of states and with it Switzerland must reduce greenhouse gas emissions much more energetically, adds Seneviratne, who also worked on the last reports of the UN Intergovernmental Panel on Climate Change: “If we want the global temperature rise to stabilize at 1.5 degrees, we have to we halve CO₂ emissions by 2030. You should see a decrease in CO₂ emissions by 2025 at the latest.”
If we don’t manage to do that, the temperatures will continue to rise and dry phases will become more intense and frequent, the ETH professor notes.
Because almost all of Europe was affected by drought and heat in 1540, that summer was even more serious than the hot summer of 2003. However, 1540 was an outlier in a phase in which the climate was actually getting cooler. The winters were much colder then than they are today.