ARCHIV - 19.07.2022, Mecklenburg-Vorpommern, Schwerin: Ein Außenthermometer in einem Kleingarten zeigt die Temperatur von knapp 40 Grad an. (zu dpa: "Vergangener Juli war weltweit einer der drei wärmsten jemals") Foto: Jens Büttner/dpa +++ dpa-Bildfunk +++

Large parts of Germany groaned under scorching heat in July: Looking back, it was the sixth warmest July for Europe, as the Copernicus Climate Change Service in Bonn announced – in Hamburg-Neuwiedenthal the German Weather Service measured this year’s heat record of 40.1 degrees Celsius. In children, old or sick people, such high temperatures can lead to circulatory problems and then become life-threatening.

And now this: In exactly that July, twelve percent more people died than the average for the years 2018 to 2021 for this month. The Federal Statistical Office calculated this in a publication on Tuesday.

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There were 85,285 deaths in the four weeks, 9,130 ​​more than the average. Especially in times of very hot temperatures, the number of deaths was increased – and the increased corona infections could only partially explain this.

It makes sense to conclude that the July heat was the main cause of the increased deaths. But is that true? Medical meteorologist Andreas Matzarakis at the German Weather Service (DWD) knows more about this. “It seems quite plausible that the heat has caused more deaths,” says the researcher in an interview with the Tagesspiegel.

Cardiovascular or respiratory diseases often fell victim to the heat. “But in order to prove the connection, experts have to wait a year and first collect all the data,” says Matzarakis.

In the subsequent analysis, the total number of deaths would be “filtered”, i.e. the deaths that would normally be expected, but also those resulting from the pandemic would be subtracted from it. In the end, the remaining “heat-related excess mortality” could indicate how many people died as a result of the heat.

“However, it is very difficult to distinguish in individual cases whether someone died from or with the heat,” explains Matzarakis. Rescue workers frequently bring patients with heart failure to the hospital during heat waves. “But when the inmates die, doctors don’t necessarily identify extremely high temperatures as the cause of death.”

Matzarakis points out that extreme heat can also lead to falls in stairwells or traffic accidents and that these increased deaths should also be included in the statistics and taken into account. Therefore, in their analysis, researchers always retrospectively compared all deaths – not just those in hospitals – with the heat.

In addition, not all heat is equally dangerous. Depending on how windy or sunny it is on a given day, or how badly pollen, ozone or forest fires have previously polluted the air, it can sometimes pose less of a risk to human health, but sometimes more. “We often see that mortality increases sharply when two or three particularly hot days follow each other,” says Matzarakis.

One thing is clear: the climate crisis is fueling heat waves, making them more frequent, more intense and longer. The number of hot days in Germany with temperatures above 30 degrees has increased significantly since 1950: from 3.6 to an average of 11.1 hot days in the years 2011 to 2020. This is the result of an analysis by the DWD on behalf of the German insurance industry.

So can we expect more heat deaths in Germany in the coming years?

“It all depends on how well we prepare people for future heat waves,” says Matzarakis. According to the medical meteorologist, in order to avoid premature deaths, people should heed recommendations even more and drink more during heat waves, shade the apartment or, if possible, move their work to the cooler morning hours. “Otherwise, we can expect even more hospital admissions, premature deaths and strains on the healthcare system.”

As a rule, the heat accumulates much more in cities than in the less populated surrounding areas – the phenomenon is known as the “urban heat island effect” and can vary between two and eight degrees. Responsible for this are large and densely built-up areas, dark asphalt on the streets, as well as insufficiently cooling trees or open water.

Waste heat from cars and air conditioning systems also heats up the urban climate. According to Matzarakis, in addition to a sensitized population, the municipalities and districts should also do more to ensure that the cities do not get too hot.

The Federal Environment Agency recommends more shade, more water, more trees and plants and more areas where rainwater can seep. This climate adaptation can take various forms and cause cooling. This includes shade awnings and blinds as well as green roofs, inner courtyards and facades. Ponds, fountains or drinking fountains can also cool down the environment.

These and other measures can ensure that residents sleep more comfortably because the interior heats up less as a result of the city climate. So-called tropical nights, i.e. nights when the temperature does not fall below 20 degrees Celsius, are particularly stressful for the elderly and the sick.