The planet is getting warmer because of human carbon emissions. With that increase in heat, the risk of extreme weather events has already doubled. Those extreme weather events include stronger hurricanes, like we witnessed when Hurricane Harvey struck Texas on Friday.
As the world warms, evaporation of our oceans speeds up, meaning that there's more and more water vapour for a storm to sweep up and dump on cities like Houston with devastating effect. Harvey was also made worse by the unusually warm waters of the Gulf of Mexico.
“This is the main fuel for the storm,” Kevin Trenberth, a senior scientist at the U.S. National Center for Atmospheric Research explained. “Although these storms occur naturally, the storm is apt to be more intense, maybe a bit bigger, longer-lasting, and with much heavier rainfalls [because of that ocean heat].”