As an expert on how extreme temperatures affect human bodies, Giesbrecht is the first to admit that he should have seen the warning signs. “After I finished throwing up, I said, ‘That’s it for the dock’ … I went and got a lawn chair and stuck it in the shallows and just sat in the lake … and chilled out,” said Giesbrecht, a professor of thermophysiology at the University of Manitoba. Amid heat warnings across much of Canada this week, Giesbrecht’s experience is a reminder of how summer heat can affect our bodies without us realizing it — and the need to watch out for potentially deadly symptoms. In Europe, more than 1,100 people have died from the heat in Spain and Portugal in recent days. There are also fears for people elsewhere in Europe and the UK – places where few have air conditioning to deal with temperatures in excess of 30C. WATCHES | Climate change is the root cause of extreme weather, says climatologist:
Canadian climatologist on the relationship between climate change and extreme weather
Dave Phillips, Environment Canada’s Senior Climatologist, says “the evidence is overwhelming” that climate change is the root cause of the increasing trend in extreme weather and weather-related disasters. Adding moisture to that heat makes it harder for us to cool down by sweating—and people can literally be cooked alive. “Our body can actually survive a drop in core temperature of 10, even 20 degrees, but our body can only survive an increase in core temperature of five [to] seven points — and then you could be in big, big trouble,” Giesbrecht said. The hotter and more humid it is, the greater the risk of heat exhaustion. Symptoms include headache, profuse sweating, clammy skin, dizziness or confusion, cramps, rapid breathing, nausea and vomiting, among others, according to Health Canada.
It’s not (just) the heat, it’s the humidity
The point at which a combination of heat and moisture becomes particularly dangerous or even fatal is explained by scientists as the “wet bulb temperature” – the lowest temperature to which an object can cool due to the evaporation of moisture. Imagine a thermometer wrapped in a wet cloth: water will continue to evaporate from the cloth up to a certain humidity level, when the air contains too much moisture for evaporation to continue. Due to the evaporative effect, the temperature of the thermometer will be lower than the air around it — that is, until evaporation stops. This diagram shows how air temperature and humidity combine for a wet bulb temperature, which explains where it is difficult or impossible for water or sweat to evaporate. This causes the core temperature of the human body to rise. (CBC News) Our body works the same way: at a wet bulb temperature of 35 C (like when it’s 40 C outside with 70 percent humidity), sweat will no longer evaporate from our body, and scientists estimate that a person can only survive about six hours in these conditions. “No matter how much water you have, it’s not going to help because you can’t maintain a survivable body temperature,” said Tapio Schneider, a climate scientist and professor at the California Institute of Technology in Pasadena. As your core temperature rises, your organs—including your heart, kidneys, and brain—begin to suffer damage, and the protein in your cells breaks down. A person with heatstroke can have seizures, fall into a coma, and die. Lower liquid bulb temperatures can also be deadly, especially for the elderly, young children, and the infirm. For example, during the European heatwave of 2003, which killed more than 20,000 people, bulb temperatures remained below 28 C. People cool off at the Dreisam River in Freiburg im Breisgau, Germany on Tuesday. Few European households have air conditioning, leaving their occupants sweltering in the current heat. (Arnd Wiegmann/Reuters) Even at this level of the wet-bulb reading, it can be dangerous to do anything that can further increase your core body temperature, such as exercise or the kind of manual labor that Giesbrecht did when he suffered from heat exhaustion. “If you’re working outdoors or working in agriculture or construction on days that are hot and humid … you’re at risk for heat stroke, cardiac stress and the like,” Snyder said. “The heat can be deadly long before you reach that ultimate survival limit.”
Stay cool and stay informed
With more hot and humid days expected this summer — and more to come as the planet gets warmer — experts say people should limit the time they spend outdoors in the heat and use air conditioning to keep cool. the living spaces. People relax on a beach in Ottawa on Tuesday as the temperature topped 31 C. Experts say people should not spend too much time in the sun, especially when it’s humid, to avoid heat illness. (Francis Ferland/CBC/Radio-Canada) Fans only help if the air temperature is cooler than your skin temperature of 33 C. If the air is warmer, the fan will only raise the temperature further, Giesbrecht said. Staying hydrated will help you sweat, while misting your body or clothes with water also has a cooling effect on your skin as the water evaporates. If someone is suffering from heatstroke, call 9-1-1 and move them immediately to a cool place — ideally an air-conditioned building or vehicle. Symptoms include high body temperature, confusion and lack of coordination, dizziness or fainting, no sweating and very hot, red skin. Instead of taking a person’s shirt off to cool them down, Giesbrecht says you should pour water on their clothes: remember the wet bulb effect? People rest in the shade on the banks of the River Thames during a heatwave in London on Tuesday (Henry Nicholls/Reuters) “The water on the shirt will evaporate and cool the skin. If you don’t have a shirt on any part of their skin, that water will just flow to the ground,” Giesbrecht said. “I’ll have a pint [of water] and pour it on that person and wait until it starts to dry, and then I’ll put some more on them so I can continue to use that cooling effect of the vapor.”
