How to handle the heat (with science)


Many are reporting that this weekend could see a heatwave in the UK. But wherever and whenever they are, intelligent humans have developed ways to cool down, some of which are more drastic than others

Hot out there. At least, that’s what people are saying. Weather forecasts are predicting a heatwave in the UK this weekend, and what could be more reliable than a weather forecast?

It’s summer in the northern hemisphere, so you’d expect it to be hot. But despite this pattern having existed for several billion years, it still seems to take people in the UK by surprise. I don't know how people in traditionally warmer countries cope with high temperatures, but I imagine it’s not by constantly pointing it out to anyone who will listen. But then, maybe climate change is messing up everyone’s heat-based coping strategies? Who can say.

In order to cool down, we need to lose heat to the external environment. But if that’s hotter than you are, it’s not easy. Modern buildings use air conditioning to deal with this, but that’s a complex and energy-intensive process, especially in comparison to “put a jumper on”, the response of parents everywhere when a child complains about being cold when indoors.

While many people seek out hot climates, sustained and inescapable heat can be dangerous. Some have recently claimed that increased global temperatures could wipe out ginger people. But ridiculous predictions aside, if a human gets too hot, it can have serious consequences like heatstroke and hyperthermia, which can occur when our cooling systems are overwhelmed. Human body temperature is a bit more varied than the simple 37C which is often quoted, but the range is rather small as the internal processes that keep us alive only occur within a narrow temperature range.

As previously hinted, the human body has evolved cooling mechanisms. Much internal heat is lost through radiation (infrared, unless you’re the Hulk perhaps). Also, if it gets too hot, we sweat. Water from inside the skin is leaked onto the outside where it evaporates, taking excess heat with it, cooling us down. However, this doesn’t work If the environment is too humid, as the air cannot hold any more water vapour, so there is nowhere for sweat to go. This is one reason humid weather feels more oppressive; we’ve lost a cooling method.

Another response is for biological processes to be slowed down or stopped. Just as shivering occurs when cold to cause muscles to do more work and produce more heat, heat production in the body is reduced when temperatures are too high, triggering behavioural responses making people more lethargic and listless. Humans are seemingly the opposite of solar-powered.

But humans are smart, and have various active means of lowering their temperature too. There are many sources that provide advice for how to stay safe during hot weather. These include logical things like avoiding too much direct sunlight, staying indoors where necessary, drinking plenty of fluids to replace those lost by sweat (and don’t forget the salts). Plus, there are plenty of “anecdotal” techniques to keep cool.

But if the heat still gets too much, there are a few options from the world of science that you could try.

Volunteer for a brain scan

Why not stay cool and further our understanding of the human brain at the same time by volunteering for a brain scan? The large magnets required for fMRIs and the like need to be supercooled, even if liquid helium is scarce. You can escape the oppressive heat and let scientists poke around (indirectly) with your brain by spending a few hours inside what seems to be a gigantic tubular fridge that keeps clicking and screaming.

It’s not as bad as I’ve made it sound there, honest.

Try anaerobic respiration

When humans respire, glucose is broken down in the presence of oxygen, resulting in adenosine triphosphate (or “ATP”, the energy source for all cells), carbon dioxide and water. This is known as aerobic respiration. However, some microorganisms respire without oxygen, known as anaerobic respiration. This produces (less) ATP, carbon dioxide, and ethanol.

If humans could do this, we could conceivably sweat ethanol instead of water, and alcohol evaporates much faster so has a more immediate cooling effect. So if you’re too hot, try shifting your metabolism to a more anaerobic mechanism. Granted, this would probably cause you to die within minutes from insufficient energy production, but at least you won’t be hot any more.

Extend your limbs

Bergman’s rule states that larger animals are found in colder environments, as if size increases, volume increases faster than surface area. Organisms with greater volume and lower surface area lose less heat so can endure cold climates better. Allen’s rule applies this to humans specifically, showing that humans from hotter regions tend to be taller and skinnier, where colder region inhabitants are rounder.

You could use the basic science underpinning this to cool your own body, by increasing your surface area and aiding heat loss via extending your limbs. How you choose to do this is up to you. Genetic engineering, physical stretching, maybe a brain transplant? These might seem elaborate and quite painful, but it’s important to stay cool.

Laser cooling

Some physics experiments can use lasers to drastically cool substances. Photons are effectively “bounced off” atoms, taking more energy from the atom than it delivers. Atoms with less energy are “colder”, in human terms. So if you’re too hot, you might want to consider standing in the path of a gargantuan laser. It could cool you down. Or vaporise you within seconds, but your component atoms should end up colder overall, so that’s a plus.

Adapt to the environment

Humans actually do eventually adapt to hot climates after a few weeks. The blood concentrations of water and salt adjust to allow greater cooling, the blood vessels alter to get more to the skin, and so on. Athletes use this process and train in harsher climates to cause more profound body adaptations. Why not take this even further and help your body cope with any extreme temperature Earth can throw at it by going for a jog on another planet? Try Mercury for a 427 °C dry heat, Venus for 462 °C in conditions that could be described as “muggy” at least, or even the surface of the sun for a casual stroll at 5505 °C.

Of course, if you can get to these places and survive in them in any conscious form, then you clearly know more science than any living human, so there’s not really a lot this post can tell you.

Reading them back, most of these methods to stay cool would almost certainly be fatal. Still, it makes a cold shower seem like a less harsh alternative, so that’s something.

Dean Burnett is one of the cool kids on Twitter, @garwboy

Powered by article was written by Dean Burnett, for on Thursday 17th July 2014 12.30 Europe/London © Guardian News and Media Limited 2010