This is how you die in extreme heat

The heated dome that roasts millions of people across the Pacific Northwest and swathes of Canada, sending temperatures in generally temperate places to record triple digits, has already claimed hundreds of lives. And these are just those we can count so far.

Climate change has increased average temperatures by 2 degrees Fahrenheit over the past century, making heat waves like this more frequent and intense than at any time in recorded history. As the heat soars, so does the death toll. A world study published last month in the journal Nature Climate Change found that global warming was responsible for 37% of heat-related deaths between 1991 and 2018. As temperatures rise more and more, that number may well rise.

Here’s what happens if you’re one of the next people to be killed by extreme heat, according to W. Lawrence Kenney, an expert in human thermoregulation at Penn State University.

First, your brain sends a series of messages to your sweat glands telling them to increase sweat production. Then your heart begins to beat faster to pump blood to the skin while the blood flow is also directed away from your liver, kidneys, and intestines. It is your body that tries to make your skin warmer than the outside air, in the hope of creating a convection phenomenon that draws heat away from you. Sometimes that alone is enough to create problems for a weak or aging heart.

If heat stroke occurs, your body can get so hot and divert so much oxygen-rich blood to the skin that it suffocates these vital internal organs, which become hypoxic. Surviving the ensuing organ failure may require an emergency transplant.

If your body fails to cool you down, its internal temperature may start to rise from a normal level between 97 and 99 degrees Fahrenheit to a level closer to 104-105 degrees.


Steve Marcus via Reuters

Paramedics shut down rescue unit in Las Vegas.

“These are situations where people die from classic heat stroke,” Kenney said in a telephone interview Thursday.

At this temperature, brain tissue is affected. You may feel that it starts off as a dull headache. For a long time, you may not know where you are or what time it is. You could collapse. You can pass out. Your brain may hemorrhage or start to swell.

As you struggle to stay awake and avoid dizzying confusion, the excessive internal heat wreaks havoc in your intestines. The gastrointestinal barrier that keeps bacteria out of your bloodstream, a protein barrier known as a tight junction, begins to open microbial valves, releasing endotoxins into the blood. Your body will likely trigger an inflammatory response. If left untreated, what follows is a cascade of organ failure that leads to almost certain death.

And that’s only part of what we know about how extreme heat kills you.

“It’s important for people to understand that there is still a lot of things we don’t know about heat stroke and who is most likely to be,” Kenney said. “This is because we cannot ethically study it in humans in the laboratory. Much of what we know comes from studies of animal models, such as mice and rats, or post-mortem examinations of people who have died of heat stroke. “

Heat can kill anyone. But it’s more likely to kill you if you’re over 65 or have heart problems.

Add to that being poor someone renting an apartment in a run down complex with no air conditioning, the kind of place the local news calls “unlivable and the heat may well kill yourself and your neighbor in just one day.

It’s important for people to understand that there is still a lot we don’t know about heat stroke and who is most susceptible to it.
W. Lawrence Kenney, Penn State University

We are learning more about how to avoid overheating. A Study 2019 by Ollie Jay, a researcher at the University of Sydney, found that electric fans cool body temperature and reduce cardiovascular strain in hot, humid weather. But, in dry heat, fans actually raise body temperature, which means access to air conditioning is crucial.

But the best insurance against death from extreme heat is probably to avoid rising global temperatures. Last year, tied in 2016 for the hottest ever worldwide. Despite a brief drop in global heating emissions as the COVID-19 pandemic has shut down factories and idle cars, we are on the right track see global temperatures rise this century by about 5.4 degrees Fahrenheit above pre-industrial averages. Changing that trajectory requires quickly and dramatically reducing the use of fossil fuels and finding ways to remove more carbon from the atmosphere than we are releasing. So far, efforts have remained largely insufficient. World oil demand, Organization of the Petroleum Exporting Countries predicted last month, will jump 5 million barrels per day in the second half of 2021 compared to the first six months.


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