Climate change aggravates the storms

Complex interaction: Hurricane Harvey and climate change

Scientists have known for decades that the maximum intensity of storms is likely to increase as temperatures rise. But it's also about the shorter time it takes a storm to reach such speeds. The temperatures in the Gulf of Mexico in late summer are now on average a little more than 1 ° C higher than 30 years ago, says Andreas Prein from the National Center for Atmospheric Research.

"If you want the car to accelerate quickly, you put the accelerator on," says Emanuel. “If you keep the accelerator depressed, the car will accelerate to its top speed. When you switch from a VW to a Ferrari, you have much faster acceleration and a higher top speed. "

Other scientists agree, including Michael Wehner, a scientist at the Department of Energy's Lawrence Berkeley National Laboratory. He points out that many Category 4 or 5 storms pick up wind speed again before reaching the mainland, but he considered it “more likely” that climate change contributed to Harvey's intensification just offshore.

RECORD RAIN

Most of the damage was caused by the incredible amount of water that Harvey brought with him. Some regions saw 1,000 millimeters of rain over a period of four days - a record in the United States. The storm drew the large amount of moisture from the ocean surface and the atmosphere.

“You have to imagine the ocean as an inexhaustible source of moisture,” says Prein. "Harvey sucked her up on land and dumped her over Texas."

With the warming of the planet, rainfall in the regions of the middle latitudes has also increased. The heat that accumulates on the sea surface due to global warming enabled the storm to absorb more water vapor than usual. Since the atmosphere is also warmer, it can also absorb more moisture.

Every scientist National Geographic has contacted agreed that the Harvey rainfall was almost certainly due to the higher temperatures attributed to CO2 emissions.

"Precipitation is the big factor here - no question about it," says Wehner. “Pretty much everything we've tried so far has indicated an increase in precipitation in such a situation. Numerous simulations take place. In every single one of them it rains more. "