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Destroyed houses and rubble following Hurricane Fiona, in Burnt Island, N.L., on Sept. 27, 2022.Frank Gunn/The Globe and Mail

Is climate change leading to more intense Atlantic hurricanes?

Recent history suggests the answer is yes, with six of the most destructive hurricanes ever recorded all occurring within the past 11 years.

The most recent, Hurricane Ian, slammed into the gulf coast of Florida in September of 2022 – the same month that post-tropical storm Fiona became the worst Atlantic cyclone to strike Canada.

In those cases and others, the storms intensified rapidly as they drew energy from ocean waters that have warmed by 0.8 degrees over the past 50 years as a consequence of climate change.

Now a new study concludes that the average intensification of tropical cyclones across the Atlantic has increased by more than 25 per cent. As a result, storms that may have been relatively weak in earlier decades are now more likely to be boosted within a day or two to something significantly more intense. With stronger hurricanes, the effect can be even more pronounced.

“I think what’s really important about that is that while we can see significant increases in the average, there’s often much larger increases in the extremes,” said Andra Garner, an atmospheric scientist at Rowan University in New Jersey who conducted the study. “It’s really serving as an urgent warning for us.”

The study, published Thursday in the journal Scientific Reports, is the latest to attempt to quantify how hurricanes are being influenced by climate change – a pressing but complex question.

While numerous studies have looked at the question of hurricane intensification in specific areas, Dr. Garner said her aim was to look more broadly.

The study is based on more than 800 tropical cyclones that occurred between 1970 and 2020 – a 50-year period that also coincides with the availability of satellite data and other measurements that make it possible to compare storms even when they don’t make landfall.

When Dr. Garner compared the first two decades of the interval with the most recent 20 years she said the trend to greater intensification was most pronounced in the southern Caribbean and the east coast of the United States.

For Canada’s Atlantic coast, the pattern is more ambiguous, with a large region of the Atlantic to the east of Nova Scotia showing somewhat less storm intensification compared with the earlier era.

Chris Fogarty, program manager for the Canadian Hurricane Centre in Dartmouth, N.S., said this picture is not a complete one because storm intensification off of Eastern Canada can occur through a different mechanism that is not related to warm ocean waters but to strong north-south temperature differences in the atmosphere.

“Fiona was a ‘textbook’ case of this,” he said.

Dr. Fogarty added that the study result may have been amplified by the fact that the 1970s and 80s were a relatively quiet period for tropical cyclones in the Atlantic.

“There may still very well be an increase in the rate of intensification but it may not be as pronounced,” he said.

Where the new study and previous work by Canadian researchers agree is in the profile of a worst-case scenario hurricane for Atlantic Canada.

Such a storm would gain intensity by moving along a track that closely parallels the U.S. east coast but would veer north, quickly crossing the Gulf of Maine and making landfall in Canada as a Category 3 or 4 storm before it has a chance to weaken.

Hurricane Juan, one of the most damaging cyclones in Canadian history, followed such a course in 2003.

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