The Earth has warmed roughly 1.8 ℉ since 1850. This means that people almost everywhere are, on average, experiencing warmer weather. But this rise in temperature is also changing humidity and rainfall, with consequences for extreme weather events, says Professor Paul O’Gorman of the MIT Program in Atmospheres, Oceans and Climate.
Warmer weather is causing more humidity. We often think about how humid it feels outside: that muggy feeling is caused by a high amount of water vapor in the air. And warmer air can hold more water; in fact, says O’Gorman, humidity rises about 3.5% for every degree Fahrenheit that the temperature rises. The higher the humidity, the harder it is for our bodies to cool off by sweating, which can be uncomfortable but also increases health risks from exhaustion, fainting, and even life-threatening heat stroke.