While the link between climate change and hurricane intensity is not yet ‘settled science’, weather experts say there is evidence that the phenomenon will lead to stronger, slower storms in future.
In recent years, Hurricanes Irma and Maria, which hit the Caribbean; Harvey, which battered Texas; and, more recently, Dorian in the Bahamas, provide compelling evidence to support the theory that this is already happening. But scientists say they are still unravelling the links between global warming and storms.
A complex range of factors can influence the size and strength of a hurricane and there is a significant amount of luck involved in where and when the most serious storms strike.
While weather experts caution that it can take decades or more for long-term weather trends to become clear, there is evidence that warming oceans, in particular, are fuelling stronger storms.
Kristiane Huber, resilience fellow at the Center for Climate and Energy Solutions in the US, told the Cayman Compass, “The fact is that warmer waters really supercharge hurricanes and a warmer atmosphere is able to hold more moisture, which means more rain.”
As the planet continues to heat, she said it was logical to expect more storms of the magnitude of Hurricane Dorian.
“There is not necessarily an increase in the number of storms expected, but the storms will have more moisture, higher wind speeds and, combined with sea-level rise, they will be more damaging.”
Huber said there was evidence that climate change was also impacting the amount of rainfall from the most serious storms. Two research groups found that record rainfall from Hurricane Harvey, which hit Texas in 2016, was significantly higher than would be expected in a world that was not warming.
The correlation between climate change and hurricanes is strong enough for the United Nations to take note.
The Intergovernmental Panel on Climate Change stated that increased incidence of Category 3 and stronger storms would be a likley outcome of climate change.
A US government summary of recent research on global warming and hurricanes also noted, “The global proportion of tropical cyclones that reach very intense (Category 4 and 5) levels will likely increase due to anthropogenic warming over the 21st century.”
Responding to questions from the Compass, the Department of Environment, National Weather Service and Hazard Management Cayman Islands, released a joint statement noting the UN’s finding and the links to Cayman.
“Given these factors, the likelihood of a Category 5 hurricane or higher intensity storm impacting the Cayman Islands is increasing,” the agencies stated.
There is no evidence, however, of an increase in frequency of hurricanes in general.
Jonathan Belles, a meteorologist for The Weather Channel with expertise on tropical forecasting and hurricanes, told the Compass there was still a lot of research to be done before too many definitive conclusions could be drawn on the precise links between climate change and storm activity.
He said it was difficult to extrapolate patterns from a limited data set. While there has been a high frequency of severe headline-making storms recently, he said this could be down to chance.
“It is definitely the case that the Caribbean has been hit by a number of strong hurricanes in the last couple of years,” Belles said. “We don’t know if that is just coincidence or a change in the climate.”
And though warming ocean temperatures do create the conditions for stronger storms, he said increases in vertical wind sheer – another impact of climate change – may be counterbalancing that effect and helping to break up storms.
One thing that is close to being settled, he said, is that storms are slowing down – a phenomenon that would explain why Dorian lingered over the Bahamas for more than three days.
Hurricane Harvey had more rainfall than similar storms in the past and there is some evidence, said Belles, that storms are getting wetter, as well as slower.
“It is possible that hurricanes may be bigger rainfall producers in the future,” he added.