Heat stress in humans from extreme temperatures and humidity will impact areas where 1.2 billion will live annually by 2100, according to a new study. This happens assuming current greenhouse gas emissions. That is more than four times the number of those affected today and more than twelve times the number of those affected without itglobal warmingin the industrial age.
High risk of heat stress in humans
Most climate research on projected heat stress in humans has focused on this topic. However, these do not take into account the role of humidity, which is another important driver.
“As we look at the risks of a warmer planet, we need to pay particular attention to the combined extremes of heat and humidity. These are particularly dangerous for human health.” Senior author Robert Kopp said.
Heat stress in humans arises from the body's inability to cool itself properly through sweating. Body temperature can rise rapidly, with high outside temperatures damaging the brain and other vital organs. Heat stress ranges from milder conditions such as heat rash and heat cramps to heat exhaustion. However, heat stroke is the most serious illness of this type. This can be fatal or cause permanent disability without emergency treatment for disease control and prevention.
In the study, the scientists examined how the combined extremes increase on a warming Earth. They used 40 climate simulations to obtain statistics about rare events. The research focused primarily on a measure of heat stress, temperature, humidity and other environmental factors. These include, for example, wind speed, sun angle, as well as solar and infrared radiation.
Study results
The annualExposure to extreme heatand moisture in excess of safety guidelines is expected to affect multiple areas. Around 500 million people currently live there. However, this will only happen when the planet warms up by 2 degrees Celsius. The Earth has already warmed about 1.2 degrees above late 19th century levels. An estimated 1.2 billion people would be affected by 3 degrees Celsius of warming, as expected by the end of this century under current global policies.
New York City is also forecast to experience extreme heat and humidity on four days in a typical year with global warming of 1.5 degrees Celsius and about eight days per year. This is comparable to the worst day of a typical year with a warming of 2 degrees Celsius. If the temperature rises to 3 degrees Celsius,according to the studyA typical year is expected to experience 24 days of extreme heat and humidity.
