Global heating made Hurricane Dorian bigger, wetter – and more deadly

(The Guardian, 4 Sep 2019) We know that warm waters fuel hurricanes, and Dorian was strengthened by waters well above average temperatures.

The Bahamas, for those who live there, is simply a place to call home. For many Americans, it’s a dream vacation spot. But Hurricane Dorian turned that dream into a nightmare. And the worst part is this is only the beginning. Because unless we confront the climate crisis, warming will turn more and more of our fantastic landscapes, cities we call paradise and other dream destinations into nightmarish hellscapes.

While the science has yet to come in on the specifics of just how much worse climate change made Dorian, we already know enough to say that warming worsened the damage. Because it’s not a coincidence that Dorian was one of the strongest landfalling storms ever recorded in the Atlantic, with the strongest sustained peak winds east of Florida, and the strongest ever to hit the Bahamas. This comes less than a year after Florida withstood the first landfalling category 5 hurricane in decades, on 5 October – the latest ever in the season for a storm that strong.

On a basic physics level, we know that warm waters fuel hurricanes, and Dorian was strengthened by waters well above average temperatures. The fact that climate change has heated up our oceans means Dorian was stronger than it would have been had we not spent the past 150 years dumping carbon pollution into the atmosphere. Sea surface temperatures were more than 1C warmer in the region where Dorian formed and strengthened than they were before we started burning fossil fuels.

Empirically, there is a roughly 7% increase in maximum sustained wind speeds of the strongest storms for each 1C of warming. Since destructive potential is proportional to the third power of the wind speed, that corresponds to a 23% increase in potential wind damage. We saw that wind damage in the heartbreaking scenes of total devastation that have come in from the Bahamas.

We know that the warmer air gets, the more moisture it can hold – and then turn into flooding rains in a storm like this. And we know that as climate change has melted glaciers and ice around the world, that water has gone into the oceans. The extra water, along with the expansion of water as it’s warmed, means that sea levels have been raised. That means when a storm like Dorian makes landfall, there’s more water for its storm surge, already bolstered by stronger winds, to push further inland.

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The Guardian, 4 Sep 2019: Global heating made Hurricane Dorian bigger, wetter – and more deadly