As climate change continues to grow in intensity, humanity has started to feel the deadly effects. Thanks to increased greenhouse gas in our environment, high temperatures and sweltering conditions will be the new norm for a growing portion of the world. And these new heatwaves are so extreme they’ll prove to be fatal.

The Study

A new study out of the University of Hawaii and published in Nature Climate Change looked at the increasing number of fatalities associated with heatwaves across the world. In total, Camilo Mora, lead author of the study, and his team looked at 1900 fatalities in 36 countries over the last 40 years. The study found that risks associated with heatwaves have increased since 1980.

Mora puts it bluntly, “For heatwaves, our options are now between bad or terrible.” In fact, 30% of the global population now live in conditions where they could experience deadly temperatures 20 days out of the year. That number will increase to 75% by 2100 if we continue down our current path of emissions. Even if we are able to drastically reduce our emissions, 48% of the population will still be at risk.

Mora explains what we are dealing with. “Dying in a heatwave is like being slowly cooked, it’s pure torture,” he says. “The young and elderly are at particular risk, but we found that this heat can kill soldiers, athletes, everyone… Finding so many cases of heat-related deaths was mind blowing, especially as they often don’t get much attention because they last for just a few days and then people moved on.”

Examples Around the World

Mora and his colleagues studied the heat and humidity levels during lethal heatwaves to try and determine what conditions must be met in order for a heatwave to turn deadly. In their research, they came across may examples that fit the bill.

In 2003, Europe experienced a deadly heatwave that sparked forest fires across multiple countries. The River Danube in Serbia became so shallow that submerged war tanks from WWII were even found. In total, the death count was estimated between 20,000 and 70,000. Again in 2010, high temperatures in Moscow, Russia contributed to the death of a further 10,000.

Example: Arizona

For a recent example closer to home, we need only look as far as Arizona and the temperatures recorded there this summer. On Monday June 19, the National Weather Service issued an excessive heat warning for Phoenix, Arizona as temperatures soared to 119 F (48.3 C).

Similar temperatures were felt throughout the rest of the state and up into California. On that same day, Palm Springs reached 116 F (46.6 C) and Sacramento hit 107 F (41.6 C). The National Weather Service warned that these high temperatures increased the risk dramatically for heat-related illnesses.

When Heatwaves Turn Deadly

Mora’s team looked to see if they could find what conditions make heatwaves fatal. It turns out, temperature is not the only factor. There are reports of people dying from heat-related illnesses in temperatures as moderate as 73.5 F (23 C). Mora explains that it’s the humidity level we need to be concerned with. He says, “Your sweat doesn’t evaporate if it is very humid, so heat accumulates in your body instead. People can then suffer heat toxicity, which is like a sunburn on the inside of your body. The blood rushes to the skin to cool you down so there’s less blood going to the organs. A common killer is when the lining of your gut breaks down and leaks toxins into the rest of your body.”

Another common illness that can also be fatal is hyperthermia - the warm cousin of the more often talked about, hypothermia. Hyperthermia is an excess of heat in the body. It can lead to heat stroke, inflammatory responses and even death.

These lethal conditions have been made worse by the clearing of trees, which naturally provide shade and cooling moisture to dry areas. Mora cautions that adapting to heatwaves by staying inside, issuing government warnings and relying on air conditioning is not a long term solution. He believes we need to do more to prevent heatwaves in the first place. The solution just may lie in curbing climate change.