Editor’s note: This post was updated on Aug. 28, 2017
As Hurricane Harvey barreled toward the coast of Texas last week with increasing intensity, forecasters were issuing dire warnings about life-threatening storm surge and torrential rain in addition to the dangerous winds that hurricanes bring.
It was no coincidence. As our climate warms, we’re experiencing ever-more devastating storm surges and record rainfalls during hurricane season – which is also why these storms are becoming more destructive and costly.
Evaporation means storms carry more water
Harvey, which formed quickly in an abnormally warm Gulf of Mexico, is dumping historic amounts of rain – 30-plus inches in the Houston area so far – with more expected, leading to catastrophic flooding in America’s fourth largest city.
So why do hurricanes bring more rain in a warmer climate? Evaporation intensifies as temperatures rise, increasing the amount of water vapor that storms pull into their systems as they travel across warm oceans. That makes for higher rainfall and more flooding when they hit land.
Unfortunately for Texas, Harvey has stalled out as a tropical storm, now drenching parts of Texas and Louisiana.
Sea level rise makes storm surges worse
Storm surge occurs when waters rise above their normal levels and are pushed inland by wind.
With Katrina, which hit land as a Category 3 hurricane, it was the storm surge that caused the levees to fail, leading to destruction to the New Orleans area. Storm surge was also responsible for an extra $2 billion in damage to New York City after Sandy hit that area in 2012, according to a Rand report.
This increasing phenomena is due, in large part, to sea level rise, which is triggered by human-caused global warming as warmer ocean water expands and land ice melts. The average global sea level has already increased by more than half a foot since the Industrial Revolution.
Storm-related flooding is on the rise
The devastating flooding we’re seeing in Houston is unusual because of its scale, but heavy rains and bad flooding are becoming the new normal in parts of our country as temperatures rise. Intense single-day rain events that cause flooding are on the rise.
Historic weather data measured since 1910 shows that in the contiguous 48 states, nine of the top 10 years for extreme one-day rain events have occurred since 1990.
We don’t yet know what kind of damage Harvey or future hurricanes will cause. But they should serve as a reminder that today, more than ever before, we need to be guided by science to help us prepare for, and act, on climate change.