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Bermuda “dodged a bullet” by avoiding severe flooding when Hurricane Humberto hit the island, according to a leading meteorologist.
Mark Guishard warned that high tides were becoming increasingly likely in Bermuda due to climate change but that the island got lucky because the tide was low when Humberto struck with a high storm surge.
Dr Guishard said Bermuda had similarly fortunate escapes when Hurricanes Gonzalo and Nicole brought large surges when the tide was low in 2014 and 2016 respectively.
He added that the western North Atlantic was encountering more intense and frequent hurricanes as the ocean gets warmer.
Dr Guishard, who runs the Risk Prediction Initiative at the Bermuda Institute of Ocean Sciences, told The Royal Gazette: “In 2014 and 2016, we dodged two bullets in terms of storm surge. Hurricanes Gonzalo and Nicole both had large surge events but they both occurred during the lowest tides.
“Preliminary indications are that Hurricane Humberto’s storm surge was higher above the predicted tide than that of Hurricane Nicole in 2016.
“Luckily, once again, Humberto’s worst surge was not coincident with high tide and the surge was thankfully short-lived.”
Roofs and walls were destroyed on many buildings when Category 3 storm Humberto lashed Bermuda with 100mph winds last month.
The island could be under threat from more strong storms in the coming years.
Dr Guishard, the former director of the Bermuda Weather Service, said: “Model studies of climate-warming scenarios point to greater frequency of hurricane passages through our part of the western North Atlantic, with intense storms projected to occur more often.
“The impacts from hurricanes are compounded by warming water, the fuel for hurricanes, and higher sea levels. So hurricane strength and storm surge will be exacerbated by climate change, all else being equal.”
Future projections of sea level in Bermuda suggest extreme high tides will become more prevalent over the next few decades. Dr Guishard said: “A warm ocean eddy in 2017 saw water levels in Bermuda rise to one to 1½ feet above the normal tide, with high-profile flooding in St George’s and other locations around the island.
“This event was not a consequence of climate change. However, projections for Bermuda and other locations globally published in 2014 indicate that such water levels, that are today considered extreme events, could be within the normal high-tide range in as little as 20 years.”
Bios has been detecting upward trends in near-surface ocean temperatures for decades and the results of its work is published in academic papers.
“Much of what we do at Bios is to understand the impact of human-induced environmental change on the deep ocean and near shore marine environment,” Mr Guishard explained.
“The Risk Prediction Initiative has published research as recently as 2016 that quantifies the relationship between sea- surface temperature and the observed maximum hurricane intensity in the Atlantic.
“On average, every degree Celsius of warmer sea-surface temperature supports fuel for an additional 17.5mph of hurricane wind speed, all else being equal.
“That doesn’t mean that all hurricanes in warmer ocean temperatures will necessarily be stronger — other factors such as dry air and wind shear will have an impact, as we recently saw in the weakening of Tropical Storm Jerry. But it means that the potential is there for stronger hurricanes.”