Hurricane Harvey, which has inundated the region since late last week, is back from its brief dalliance in the Gulf of Mexico. While away, it renewed its strength and picked up even more rain. Today's deluge adds to the 20, 30, and 49 inches of rain that have fallen across the region in the days since Thursday, toppling existing records as part of what some are calling a one in 500 year flood.
It’s hard to watch this disaster unfold without asking how such scales of destruction are even possible. And it’s hard not to answer that question without considering climate change, the hidden factor that has made Harvey much worse than it could have been.
NASA and the National Oceanographic Institute (NOAA) describe tropical cyclones like Hurricane Harvey as “engines that require moist air as fuel.” That need for heat is why the Atlantic hurricane season stretches from June through November. Tropical cyclones only form over ocean waters that maintain a temperature of at least 80 degrees Fahrenheit for 165 feet below the surface, and that’s the time of year when the Atlantic Ocean is most likely to be so warm. Just add wind, and you've got yourself a hurricane.
But warmer waters don’t just make hurricanes more likely to form—they also make them more severe. And it's here where we can see the fingerprints of climate change on Harvey.
“For every degree centigrade the ocean surface heats up, you get about a seven percent increase in water vapor in the atmosphere,” says James Masters, the director of meteorology for Weather Underground.
“In the Gulf of Mexico, where Harvey drew its strength from, the temperature was about a degree centigrade above average for this time of year,” he explains. “And a great part of that extra heat energy was due to the fact that this year, the planet as a whole is experiencing its second warmest year on record.” Read More