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.
Had Dorian been moving at a regular pace of a few miles an hour, the devastation in the Bahamas would have been much less severe. But because it sat in place, basically stationary, the damage has been catastrophic. Again, Dorian is far from unique in moving slowly, as a study last year found a 10% decrease in speed for storms like this globally, while a similar study found a 17% decrease along the east coast of the US. While neither of these studies directly tie that slowdown to climate change, the theory that climate change is changing the jet stream in ways that would lead to stalling storms (a phenomenon one of us has researched) is growing increasingly convincing.
Source: https://www.theguardian.com/commentisfree/2019/sep/04/climate-crisis-hurricane-dorian-floods-bahamas