Heat and drought are the greatest dangers

The fight against climate change can only be won through global cooperation. However, it would be naive to expect otherwise. This is the conclusion of Dr. Michael Sachweh, a meteorologist and climate researcher from Erdingen. His advice is therefore to place more emphasis on preparing for the inevitable consequences of climate change. After all, this is where people will feel the effects of climate change most acutely.

“Rhine water levels continue to fall,” ‘Drought alert throughout Germany,’ ‘Drought visible from space’... This summer's headlines do not surprise meteorologist Dr. Michael Sachweh. In his opinion, heat waves and droughts are the greatest challenges that climate change poses for our latitudes – for both nature and people. If climate change continues unabated – and Dr. Michael Sachweh sees no reason to believe otherwise – the heat-related hospitalization rate is likely to have increased at least fourfold by the end of the century, and tenfold in some regions of Germany. In addition, heat and drought are already responsible for many deaths – more than media coverage suggests. “Therefore, protecting against heat waves seems most important to me. This requires many more air-conditioned rooms, especially in nursing homes and hospitals,” he says. Because when it comes to air conditioning, Germany is still a developing country.

Michael Sachweh is a meteorologist for Bayerischer Rundfunk. But he has also been active in climate research, has written several books on meteorology and was most recently the lead meteorologist at the European Athletics Championships in Munich. He is also world-famous as a storm chaser, researching severe storms and tornadoes in the American Midwest and hurricanes on the coasts (see his book Stormchasing, Delius Klasing Verlag). Climate and its interrelations, as well as the consequences for our weather, are part of his professional life. The man from Erdingen looks at it with the sober eyes of a scientist. “Climate change also has advantages, for example, when the polar seas become ice-free and the sea route to Asia is significantly shortened, which boosts merchant shipping and makes goods cheaper. But it also has negative consequences that we have to guard against,” warns the meteorologist, presenting a whole series of diagrams. They illustrate these consequences.

Climate change is man-made

Since the mid-1980s, the average annual temperature on the globe has been rising continuously. Time and again, the previous records have been broken. Meanwhile, the global temperature is on average one degree higher than the average for the years 1951 to 1980. “This is where anthropogenic, man-made climate change is evident,” emphasizes Dr. Sachweh. The immense emission of carbon dioxide from the combustion of fossil fuels is responsible for this. It is growing exponentially. Since 1950, this value has increased sevenfold. Every year, humanity blows around 35 billion tons of carbon dioxide into the air, and even the minimal decline of the past two years due to the coronavirus pandemic doesn't really change anything. The atmosphere is becoming enriched with this gas; this prevents the heat energy generated by the sun at the earth's surface from being completely released back into space. Instead, the atmosphere heats up – the greenhouse effect.

This primarily leads to more dryness and more prolonged periods of heat and drought in our region, as we have once again experienced this summer of 2022. In Germany, it is also getting warmer from year to year. Statistically, the number of hot days is increasing significantly, while the number of days with snow cover in winter is decreasing and the average annual temperature is rising.

Recent years have been marked by severe storms such as “Friederike” or the trio “Xandra”, “Ylenia” and “Zeynep” in February 2022. We are also in the year following “Bernd”, the low-pressure system responsible for the largest and deadliest natural disaster in Germany. How does that fit together?

The low-pressure areas are moving more slowly

“A stormy winter is not yet a long-term trend,” Dr. Michael Sachweh points out. Although the past few years have been marked by severe storms, the statistics show that the number of cyclones worldwide has not increased. In Germany, too, in the long-term view over the past seven decades, not more days with gale-force winds have been registered, but significantly fewer.

This, too, can be explained by climate change. One of its characteristics is that the polar regions warm more than the tropics. The global north-south temperature difference, which drives the development of storm lows, is thus decreasing. As a result, major winter storms are becoming rarer.

When it comes to heavy rain, the mechanisms are also more complicated than initially thought. A glance at the statistics shows Dr. Michael Sachweh that the number of days with precipitation of more than 20 liters per square meter in Germany has not increased, but the curve even points slightly downwards. So there are not more days of heavy rain, but... “Climate change favors extreme, spatially concentrated heavy rain,” Dr. Sachweh continues. The clouds discharge their rain masses more heavily at one point because the low-pressure areas move more slowly. This, in turn, is a manifestation of climate change. This is because the speed of the highs and lows is determined by the jet stream, or more precisely the polar jet stream, a fast band of wind in the higher layers of the weather sphere of the atmosphere (troposphere). Like a conveyor belt, the jet stream controls the sequence of high and low pressure areas over the Earth's northern hemisphere. “The current has slowed down, which means that weather systems remain in one place for longer and rain there for longer – the most recent example is the devastating low-pressure system 'Bernd' in July 2021, which led to the Ahr Valley flood disaster. For the same reason, high-pressure phases last longer and thus increase summer heat and the risk of drought,” explains the meteorologist.
 

Trend reversal? Unlikely

The bottom line is that the insurance industry, along with the economy and other areas of life, must prepare for more heat waves, droughts and heavy local rainfall events, Dr. Sachweh summarizes. Of course, everything must continue to be done to combat climate change, but ultimately the expert has no illusions. The largest CO2 emitters are China, the United States, India and Russia; in China in particular, coal consumption is still growing. Dr. Sachweh: “A sustainable containment of the warming trend can only be achieved through global cooperation on climate protection. This must be done by all the nations that have played a major role in the warming trend. It is commendable to strive for this – but naive to consider success likely.”