Humans actually cope with heat quite well, our body can withstand a lot, thanks to sweat glands and a richly branched network of blood vessels that help prevent heat build-up.

A hot day doesn't do much harm.

It only becomes dangerous when the heat turns into continuous hot days and hot nights, and when it even turns into a heat wave that lasts for weeks.

Then at some point our body can no longer recover.

Heat exhaustion comes first, then heat stroke.

Joachim Müller-Jung

Editor in the feuilleton, responsible for the "Nature and Science" department.

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But it's not just the duration of the heat: The peak load with temperatures over 50 degrees puts the unprotected body to an extreme test.

Because our body is constantly trying desperately to maintain an optimal internal temperature of 37 to 38 degrees.

This is how the organs function optimally.

If it goes over 40 degrees, i.e. with a high fever, it becomes critical.

Deadly heat waves have been around long before climate change.

But now the number of months with heat records has quintupled worldwide, and in parts of Europe or Africa even tenfold, since humans accelerated the warming of the earth with their greenhouse gases.

News like this sends chills down the spines of doctors, especially in large cities and metropolitan areas.

This is because the number of people at risk of heat stroke is also growing rapidly.

Climate researchers have calculated that if global warming continues as before, the number of temperature records in thirty years will be twelve times higher than without climate change.

A third of all people now live in areas that experience dangerous heat for at least twenty days a year.

Researchers from Hawaii have calculated: In the year 2100, 74 percent, i.e. three out of four people, could live in such regions of the world.

More and more people are threatening to experience first-hand what has recently been happening more and more frequently: hundreds, even thousands, of heat deaths in one year – and practically in the neighborhood.

In 2003, heat waves in Europe killed 70,000 people as a result of extreme temperatures both indoors and outdoors, in 2010 there were 7,000 in the United States and at least 10,000 in Moscow alone.

So if you are happy about hot temperatures or even about being heat-free, you should always consider the downside.

Our body, even the physics, is extremely challenged.

Often dangerously overwhelmed.

However, more extreme temperatures not only bring people to their limits, but also animals, plants and ultimately even machines.

airplanes, for example.

When air heats up, it expands and the density of the air decreases.

This brings aircraft to the limit when braking, either the runways have to be lengthened or the weight of the loaded aircraft reduced.

In fact, numerous flights have had to be diverted or canceled on extreme days because of this.

The air is different in the heat.

Our body has to struggle with the extreme heat, especially when it is paired with high luminous humidity.

Then heat "feels" even more brutal.

The body is then even less able to regulate the temperature through sweating.

We are practically at the mercy of the heat, even with the internal air conditioning running at full blast with increased blood flow and sweating.

The sweat does not dry on the skin and therefore does not cool down.

If the body temperature rises above 39 degrees for a longer period of time, the brain switches to fatigue, the muscles become sluggish, the blood supply to the skin decreases, the body no longer sweats and the outside suddenly feels cold.

Inside it heats up more and more.

Until the brain overheats, thinking slows down, confusion sets in, dizziness sets in - even to the point of fainting.

That's the heat shock.

At body temperatures well above 40 degrees, the cells and their building blocks, the proteins, fall apart and the vital organs eventually fail.

Effects of heat on adipose tissue

It is also critical, as research has shown more and more clearly, when the body does not get a rest - when the heat wave also pushes up nighttime temperatures and keeps them up.

Older, weakened people in particular are often defenseless against overheating.

That is why the major heat waves of the recent past have mostly killed old, sick people in big cities and in houses without air conditioning.

But even the others, who are better able to put up with it, have to reckon with the consequences.

Doctors have long had unambiguous statistics showing how the heat waves are driving up the number of diabetics.

In the heat, our brown - the "good" - fatty tissue no longer functions properly, which burns excess energy from food and converts it into heat.

The result: people store the energy as depot fat, become fatter and at some point – sooner rather than later – develop diabetes.

With the current global warming, that could mean at least 600,000 more diabetics worldwide by 2040. But it is precisely these people who are at additional risk in extreme heat.

You suffer a heart attack earlier than non-diabetics.

And that does not affect the very old people, but even the younger ones, if they only get diabetic early enough.

Therefore:

Exercise and good blood circulation throughout the year is certainly the best protection against the effects of heat.

And lets us continue to think clearly even when the hot air in front of our eyes doesn't stop flickering.