Jump directly to the page contents

Climate change

What the heat does to us

Picture: shutterstock

Once again, we are experiencing a summer with record heat and drought. With consequences for people and nature.

Over several days temperatures reached up to 40 degrees Celsius during the day and over 25 degrees at night. The prevalence of such conditions across parts of Germany in recent weeks means that the summer can become a medical emergency. The longer the heat wave lasted, the more men and women suffered from headaches or dizziness or even ended up in emergency departments; dehydrated, confused, with circulatory collapse, or because their medication, for example, against high blood pressure or schizophrenia, was no longer working.

Elderly people, small children and heart or lung patients were particularly affected, including many coronavirus patients, but also healthy people. Claudia Traidl-Hoffmann, Director of the Institute of Environmental Medicine at Helmholtz Munich and co-founder of the Center for Climate Resilience at Augsburg University Hospital, knows of roofers and harvest workers, kindergarten children and joggers, homeless people and attic dwellers whose bodies gave out as a result of the hot days and lack of coolness at night. And many thousands died, once again.

In the summers of 2018 to 2020 alone, nearly 20,000 men and women died from heat in Germany, according to a recent study. "That's twice as many as in road traffic accidents, and in just a few days," Traidl-Hoffman warns. "Yet heat deaths are preventable deaths." With her team, she is therefore pursuing a vital research question: How do you protect people from the increasing heat?

Oops, an error occurred! Code: 20220928225342c602d650

Claudia Traidl-Hoffmann, Picture: A. Heddergott/TUM

What heat waves do to the body is now well researched. "In short, they make healthy people groggy and sick people sicker," explains the environmental physician. The heart, lungs and blood vessels are stressed as the body tries to cool its core temperature down to 37 degrees. You sweat, lose fluids, your face turns red, and it's harder to concentrate. If the body continues to overheat, a dangerous process is set in motion. From 42 degrees, the blood begins to clot too much, then not at all. The brain swells, the kidneys no longer filter toxins out of the body; multi-organ failure is imminent. If the proteins denature, any help will be too late: Like a boiled egg, there is no way back. It doesn't matter whether the patients are 82, 20 or two years old.

People in regions or city districts that already suffer from air pollution are at additional risk. In these areas, chemical reactions lead to an increase in nitrogen dioxide, ozone and particulate matter pollution. "If we succeed in reducing air pollution there, for example, through speed limits or less individual traffic, the health of the residents will benefit twice over," explains Traidl-Hoffmann. "On normal days and especially during hot days." At the same time, emissions also put the brakes on the drivers of the climate crisis; a triple-win effect, so to speak.

[Translate to Englisch:]

[Translate to Englisch:]

Auch die eigene Branche nimmt ihr Zentrum unter die Lupe. Genauer: dessen Beitrag zum Klima- und präventiven Gesundheitsschutz. So erforscht das Projekt „Green Hospitals“, wie Kliniken ihre Häuser sowohl emissionsärmer als auch hitzeresistenter betreiben können.

Um zu ermitteln, wann welche Menschen bei Hitzewellen welche Art Hilfe benötigen, entwickelt es außerdem ein Hitze-Register. Retrospektiv werden darin Krankendaten und Diagnosen mit Wetterdaten verknüpft, um Zusammenhänge zu erkennen. Dank ihnen können sich Ärzt:innen und Krankenhäuser in Zukunft besser vorbereiten.

Oops, an error occurred! Code: 20220928225342f9e00f6d

The institution's own industry is also taking a close look at its center. More precisely; its contribution to climate and preventive health protection. For example, the "Green Hospitals" project is researching how hospitals can operate their facilities with both lower emissions and greater heat resistance.

It is also developing a heat register to determine when people need what kind of help during heat waves. In this register, illness data and diagnoses are linked retrospectively with weather data to identify correlations. Thanks to this, doctors and hospitals will be able to prepare better in the future.

Last but not least, Traidl-Hoffmann, together with the German Climate Change and Health Alliance (KLUG), advises, among others, the Bavarian state government on the development of a climate-resilient health care system, especially heat protection plans. France is a role model. There, weather services warn hospitals, schools or social services in good time of heat waves so that they can take necessary protective measures such as shading and cooling rooms, ensuring sufficient fluid replenishment, adjusting medication, canceling sporting events. "That's how you save lives," says the medical expert. "Germany needs to be much more active in this."

Neither drinks nor awnings help against droughts. Many farmers and foresters are now suffering from them for the third year, complaining about crop failures and fearing for their livelihoods. Andreas Marx of the Helmholtz Centre for Environmental Research Leipzig (UFZ) cannot allay their fears, but he can at least show them how the situation is developing.

Andreas Marx / Helmholtz Centre for Environmental Research– UFZ in Leipzig. Picture: UFZ

Since 2014, he has been coordinating the Drought Monitor: An online tool that provides daily updated data on soil moisture in Germany. At the click of a mouse, three maps with colors ranging from blue to dark red show the current situation (or optionally a 14-day retrospective), down to a soil depth of 1.8 meters, and in topsoil down to a depth of 0.25 meters, which becomes moist more quickly after rain and can hold the water better or worse depending on its composition. This so-called plant-available water is shown on the third map of the same name; it thus gives farmers an indication of how thirsty their crops or fruit trees are and whether it makes sense to irrigate.

What role does heat play in this? "Droughts can occur even without heat," Marx explains. "But high temperatures are a major driver because they accelerate evaporation." For example, at 30 degrees air temperature, up to six liters of water evaporate per square meter per day, literally dissolving into thin air and lost to the soil and the plants or trees growing there. Every degree more increases evaporation.

UFZ Drought Monitor for the 01.08.2022. Source: UFZ

The overallsoil map in mid-July 2022 makes it clear what the combination of a long-lasting lack of rain and many heat days is causing: Only in the Alpine region, the Bavarian Forest, and between the North Sea and western Baltic Sea coasts is there no drought. The Black Forest region, Franconia, and almost all of eastern Germany south of the Elbe River, with the exception of the Harz Mountains and the Thuringian Forest, are colored red to deep red (extreme to exceptional drought). The rest of the country varies from yellow (exceptionally dry) to orange (severe drought). "This situation is now continuing for the third summer in a row," says Andreas Marx. "For Germany, this is completely new."

He also knows the consequences: In 2018 alone, agricultural losses were estimated at 700 million to three billion euros. In addition, there is massive damage to forests and woodlands because the starving spruce trees in particular can no longer defend themselves against bark beetles. Whole swaths of land are falling bare, making it obvious to everyone that the climate crisis has long since taken its toll.

The drought monitor is based on simulations with the so-called mesoscale hydrological model. It was developed at the UFZ and is becoming increasingly popular at other research institutions. Every night it is fed with data from 2500 measuring stations of the German Weather Service as well as from 40 of its own soil moisture measurements, with the modeled results then being prepared as a map.

These are used by a wide variety of interested parties: By farmers and foresters as well as advisory institutions, by seed developers and risk insurers, by river navigation and drinking water associations, which are also increasingly running out of resources, and–this is also new in Germany–by fire departments. "The drier forest soils are, the more flammable they are. Heat dries out the topsoil in particular, so the risk of forest fires grows extremely on hot days. A discarded butt, a misfire on the catalytic converter, and a spark can turn into dangerous flames," Marx knows. "That's why more and more forest areas are being closed off. I'm afraid our forests will burn like in southern Europe in the foreseeable future."

All the more important is the question of what will happen next with the heat? Astrid Kiendler-Scharr, director of the Troposphere Institute for Energy and Climate Research in Jülich, Germany, and lead author of the latest IPCC report, or more precisely, of the chapter on "Short-lived climate pollutants," which was included there for the first time, can answer this question. "The hot temperatures we have been suffering from in this country lately are fueled by the currently measured 1.1 degrees more compared to pre-industrial times," explains the physicist.

These are used by a wide variety of interested parties: By farmers and foresters as well as advisory institutions, by seed developers and risk insurers, by river navigation and drinking water associations, which are also increasingly running out of resources, and–this is also new in Germany–by fire departments. "The drier forest soils are, the more flammable they are. Heat dries out the topsoil in particular, so the risk of forest fires grows extremely on hot days. A discarded butt, a misfire on the catalytic converter, and a spark can turn into dangerous flames," Marx knows. "That's why more and more forest areas are being closed off. I'm afraid our forests will burn like in southern Europe in the foreseeable future."

All the more important is the question of what will happen next with the heat? Astrid Kiendler-Scharr, director of the Troposphere Institute for Energy and Climate Research in Jülich, Germany, and lead author of the latest IPCC report, or more precisely, of the chapter on "Short-lived climate pollutants," which was included there for the first time, can answer this question. "The hot temperatures we have been suffering from in this country lately are fueled by the currently measured 1.1 degrees more compared to pre-industrial times," explains the physicist.

Astrid Kiendler-Scharr, Forschungszentrum Jülich. Picture: Forschungszentrum Jülich, Ralf-Uwe Limbach

"What's clear is that by 2050, the number of heat days will increase, by more than two weeks in particularly affected regions, even if we manage to meet the Paris climate targets." A Hamburg summer will then feel like Milan today, Cologne like Palermo.

The reason: Every gigaton of CO2 that we released into the atmosphere in the past will have an effect for decades to centuries. Kiendler-Scharr is therefore researching climate pollutants that contribute just as much to global warming as CO2, but are much shorter-lived: Methane, for example, ozone, nitrogen oxides or other fine dust aerosols.

"These substances offer us a powerful adjusting screw because they only remain in the atmosphere for a few hours to a maximum of twelve years," says Kiendler-Scharr. "If we reduce them effectively, we can slow warming by up to 0.8 degrees by 2100. And I can't say it often enough: Every hundredth of a degree counts to protect us from even more extreme events like heat waves!"

To collect as much and as accurate data as possible for computational models, her Jülich institute has spent more than 20 years equipping airliners with measuring equipment, building the SAPHIR atmospheric simulation chamber, and most recently, in the first Corona spring of 2020, using a flying blimp to determine how much short-lived climate pollutants have decreased during the lockdown. The answer is somewhat discouraging: Only by seven percent.

The SAPHIR atmospheric simulation chamber enables reproducible investigations into precisely defined atmospheric-chemical mechanisms. Picture: Forschungszentrum Jülich

The good news is that we now know exactly where man-made methane emissions come from. Mainly from natural gas, livestock and landfills. And therefore, what measures we need to stop them: "We need to consistently switch to renewable energy, insulate our buildings and fix leaking gas lines," Kiendler-Scharr demands." "Less beef and milk, better waste cycles and so on."

The situation is more complicated with particulate aerosols. They come from exhaust gases and biomass burning, but also from natural sources such as desert dust and sea spray, and also form from substances released into the atmosphere by plants. Accordingly, they differ in their physical and chemical composition and in their effect on the climate. In the Jülich atmospheric chamber, it has nevertheless been possible to determine the basic processes of how different aerosols form and grow. Kiendler-Scharr's team is currently investigating how exactly they affect the climate.

Known pollutants such as carbon monoxide can be significantly reduced, for example, through better particulate filters, fewer combustion engine cars, or speed limits. This has a doubly positive effect: The air becomes cleaner, which means fewer people get lung and cardiovascular diseases, with and without heat waves. Which brings us back to the topic of health.

Kiendler-Scharr emphasizes: "Our model calculations show that it is possible to slow down global warming by reducing emissions. Now it's up to policymakers to act."

Oops, an error occurred! Code: 20220928225342adc0032f

Readers comments

As curious as we are? Discover more.