About a third of the global population experiences over 20 days of deadly heat per year. Findings of a new study now estimate that this number will rise by at least 50 percent by the year 2100.
Killer Heat Days
In a new study, researchers from the University of Hawaii looked at the heat waves that occurred between 1980 and 2014 and then identified a threshold past which indicates the condition of humidity and heat can be fatal.
By comparing their findings with climate predictions for the next eight decades, the researchers found that heat-related deaths will become more common in the future. The analysis also revealed that if the level of carbon emissions continue, dangerous heat waves may affect up to three-fourths of the global population.
Study researcher Camilo Mora of the University of Hawaii and colleagues created an interactive global map with data from computer simulations and past heat waves to determine what will be the frequency of heat waves under different scenarios of carbon dioxide emissions.
Under current levels of carbon emissions, the map shows the entire eastern United States will experience a significant number of killer heat days. Other regions, which include Southeast United States, Central Africa, much of Central and South America, Pakistan, Australia, and much of Asia, will experience more killer heat days.
The researchers showed that the overall risk of illness or death linked to heat has steadily increased since 1980.
About 30 percent of the global population now live in climatic conditions with killer temperatures at least 20 days per year, but the percentage of people who will become at risk by 2100 will increase to 48 percent regardless if the emissions are drastically lowered. About three-quarters of the world's population will likewise be under threat by 2100 if the emission of planet-warming greenhouse gases is not reduced at all.
"An increasing threat to human life from excess heat now seems almost inevitable, but will be greatly aggravated if greenhouse gases are not considerably reduced," Mora and colleagues wrote in their study, which was published in Nature Climate Change on Monday, June 19.
The researchers explained how rising temperatures can be fatal.
"Your sweat doesn't evaporate if it is very humid, so heat accumulates in your body instead," Mora said. "People can then suffer heat toxicity, which is like 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."
How Societies Can Adapt To Rising Temperatures
Although people can't change how their bodies react to heat within a short timescale, there are ways that can allow people and societies to adapt to climate change. People can use technologies such as air conditioning. Governments can also come up with ways to keep people from dying because of the heat.
The United States Environmental Protection Agency (EPA), for instance, has encouraged cities in the country to mitigate the increase in temperatures by observing sustainable building practices. Some cities now also factor in the rising temperatures into planning and already started planting more greenery and using heat-reflective building materials.