Dorian is the second-strongest Atlantic storm on record. That seems to be part of a worrying trend

IF HURRICANE stories feel like an annual ritual for news organisations every autumn in the northern hemisphere, that is because they are.

Last year was the third in succession of storms in the Atlantic of above-average intensity. Hurricane Dorian suggests this year may follow suit. It is the second-most powerful Atlantic storm recorded, and the strongest-ever to pound the Bahamas, where damage is described as “catastrophic”. Storm-surge and hurricane warnings have also been issued for long stretches of the American coast. Some nursing homes and hospitals have been evacuated and residents are braced for torrential rain from Tuesday morning.

Many see these yearly extreme-weather disasters as a trend, and blame it on climate change. Scientists are cautious about making that link, as a number of exceptional years in a row may still be exceptional. Indeed, climate change does not yet appear to be making hurricanes more frequent. Climate experts, however, are increasingly persuaded that global warming is making them more severe. Rising levels of greenhouse gases in the atmosphere are driving up sea-surface temperatures. In turn, warmer oceans mean more intense and longer-lasting storms.

Indeed, research by the American government’s National Oceanic and Atmospheric Administration finds a correlation between rising sea-surface temperatures in the Atlantic and an index measuring the combined frequency, intensity and duration of hurricanes.

Moreover, climate change is also causing sea levels to rise, as hotter water expands and polar ice melts. This makes the storm surges that accompany hurricanes more damaging. When Dorian was ravaging the Abaco islands in the Bahamas, a surge higher than a two-storey building brought devastating flooding.

A third factor that may be linked to climate change is the more frequent “stalling” of storms—as has happened with Dorian this week. A recent study by NASA and NOAA showed that over the past seven decades North Atlantic hurricanes have been moving slower and meandering farther from their average trajectory. The result has been storms that linger for longer periods of time near the coast, leading to more rainfall, and more flooding.