Slow, intense and unrelenting: The science behind Dorian

Volunteers rescue families in Freeport in the bahamas on tuesday. Climate scientists say the hurricane had hallmarks of what hurricanes will increasingly look like as the climate warms.

The science connecting climate change to hurricanes like Dorian is strong. Warmer oceans fuel more extreme storms; rising sea levels bolster storm surge and lead to worse floods.

Just this summer, after analyzing more than 70 years of Atlantic hurricane data, NASA scientist Tim Hall reported that storms have become much more likely to "stall" over land, prolonging the time when a community is subjected to devastating winds and drenching rain.

But none of the numbers in his spreadsheets could prepare Hall for the image on his computer screen last week: Dorian swirling as a Category 5 storm, monstrous and nearly motionless, above the Bahamas.

Seeing it "just spinning there, spinning there, spinning there, over the same spot," Hall said, "you can't help but be awestruck to the point of speechlessness."

After pulverizing the Bahamas for more than 40 hours, Dorian finally swerved north to the U.S. mainland.

"Simply unbelievable," tweeted Marshall Shepherd, an atmospheric scientist at the University of Georgia and former president of the American Meteorological Association. "I feel nausea over this, and I only get that feeling with a few storms."

The hurricane has matched or broken records for its intensity and for its creeping pace over the Bahamas. But it also fits a trend: Dorian's appearance made 2019 the fourth straight year in which a Category 5 hurricane formed in the Atlantic — the longest such streak on record.

Shocking though the storm has been, meteorologists and climate scientists say it bears hallmarks of what hurricanes will increasingly look like as the climate warms.

Dorian's rapid intensification last weekend was unprecedented for a hurricane that was already so strong. In the space of nine hours Sunday, its peak winds increased from 150 mph to 180 mph.

By the time the storm made landfall, its sustained winds of 185 were tied for strongest ever observed in the Atlantic.

The link between rapid intensification and climate change is robust, said Jennifer Francis, an atmospheric scientist at Woods Hole Research Center.

Heat in the ocean is a hurricane's primary source of fuel, and the world's oceans have absorbed more than 90% of the warming of the past 50 years, according to the National Oceanic and Atmospheric Administration.

The water that Dorian developed over was about a degree Celsius warmer than normal, Francis said: "That translates to a whole bunch of energy."

Because warm air can hold more moisture, climate change has increased the amount of water vapor in the atmosphere, leading to wetter hurricanes that unleash more extreme rainfall.

The warm, wet air also gives further fuel to a growing storm.

"When that water vapor condenses into cloud droplets, it releases a lot of heat into the atmosphere and that's what a hurricane feeds off of," Francis said. "These factors are very clearly contributing to the storms we've been seeing lately."

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