Like many other Finns I go to the sauna several times per week. I love the sensation of heat and humidity generated by a proper sauna, where the temperature is around 80°C, and where you can control the humidity by throwing water on the stones. Obviously you spend only about 10-15 minutes in a sauna that hot.

Paradoxically, I’m not too comfortable with hot and humid summer days, especially if they go on for a long stretch of time. This summer in Finland we had a 30-day streak when the thermometers surpassed our “heat threshold” of 25°C. Now, I realize that people living close to the equator might have a different sense of what’s hot and not, but for us, in a country by the Arctic Circle, it was yet another record hot summer.

It’s hard to imagine what it would be like to live in a place where the temperature lingers above our bodies' own healthy internal temperature for longer periods of time, day and night. What if critical parts of the infrastructure, such as power distribution and logistics, would fail and access to cool water and air conditioning would be disrupted?

In his bestselling near-future sci-fi book The Ministry for the Future, Kim Stanley Robinson describes in a gruesome way how a prolonged heatwave in India leaves 20 million people dead. Some of the passages are hard to read as he details how the systems in a human body that enable it to adapt to heat become overwhelmed and what happens when the ability to sweat shuts down.

We know that when perspiration is dried by the air there is a cooling effect on the body. However, once a person stops perspiring, a person can very quickly move from heat exhaustion to heat stroke. The transition from heat exhaustion to heat stroke is dangerous, requiring emergency treatment.

Untreated heat stroke can quickly damage your brain, heart, kidneys and muscles, and delayed treatment increases the risk of serious complications or death. Here’s how an expert from the CDC describes it in Scientific American:

It begins with perspiring profusely, and when that shuts down, the body becomes very hot. Eventually that begins to affect the brain, and that's when people begin to get confused and can lose consciousness.

The analogy we use is if you're driving a car and you notice that the temperature light comes on, what's happening is the cooling system of the car is becoming overwhelmed. If you turn off the car and let it cool eventually you can start driving again. But if you continue to drive the car, the problem goes beyond the cooling system to affect the engine, and eventually the car will stop.

So, I guess we just have to cross our fingers and hope that we don’t encounter too many heatwaves in the future. Unfortunately, the latest IPCC climate report, released on August 9th 2021, is very clear when it comes to hot extremes and heatwaves:

With every additional increment of global warming, changes in extremes continue to become larger. For example, every additional 0.5°C of global warming causes clearly discernible increases in the intensity and frequency of hot extremes, including heatwaves (very likely), and heavy precipitation (high confidence), as well as agricultural and ecological droughts in some regions (high confidence).

Obviously we need to do something about global warming if we want to prevent heatwaves and other weather extremes from becoming more and more frequent in every region across the globe. The best way to do it is to stop adding CO2 and other greenhouse gases (GHGs) to the air as soon as possible and develop new technologies for removing large amounts of carbon from the atmosphere.

I seriously hope that sufficient efforts for reaching carbon neutrality can be coordinated globally before a truly devastating and deadly heatwave, like the one described in The Ministry for the Future, occurs. That would be a terrible wake-up call.