Massive storms on the rise
RESULT OF GLOBAL WARMING: INCREASED AMOUNT OF VAPOUR IN WEATHER SYSTEMS
Climate shift also sees storms slow and unload a deluge equal to a year’s rain.
Global warming has increased the likelihood of more massive, sluggish storms like Florence, capable of dropping record amounts of rain and causing the type of catastrophic flooding that crippled North and South Carolina this week, experts say.
Most meteorologists agree that climate change can increase the volume of water vapour stored within weather systems. More water vapour means more rain, especially when the storm is a crawler like Florence, which slowed to about 1.6km/h after slamming into the North Carolina coast.
When storms such as Harvey, which struck Texas last year, and Florence virtually stalled, a deluge of rain can fall in days, equal to the amount an area typically sees in a year, they said.
“It is compelling and sobering to see these storms come in backto-back seasons,” said Jim Kossin, an atmospheric research scientist with the US National Oceanic and Atmospheric Administration. His research suggests that global warming has affected the speed of storms and the amount of moisture they contain.
Florence, which has killed at least 36 people, dumped up to 91cm of rain in parts of North Carolina since yesterday. At least 16 rivers remained at major flood stage, with three others set to crest in the coming days in North Carolina, the state said.
It has been a little more than a year since Hurricane Harvey dumped trillions of litres of water on Texas and the US Gulf Coast, killing 68 people.
Based on data from about seven decades of storms, Kossin found tropical cyclone speed had decreased globally by 10% from 1949 to 2016, according to a paper published in June in the scientific journal Nature.
The reason is that climate change is warming the Arctic much more than it is heating up the tropics, easing the pressure difference between the two, he said. Pressure differences drive the winds, he said.
In the case of Florence, warmer sea temperatures and the amount of moisture in the air may have increased rainfall by 50% in the hardest-hit areas, according to a study by researchers at Stony Brook University, Lawrence Berkeley National Laboratory and the National Centre for Atmospheric Research.
Florence was also about 80km larger in diameter due to global warming, the study showed.
“There will be both more inland flooding, storm-surge and ocean-related flooding because the sea is getting higher,” said Brion Callori of commercial property insurance firm FM Global. – Reuters