Last month, forecasters watched in horror as Hurricane Melissa barreled across the Atlantic Ocean, turned into a monster and made landfall in the Caribbean. As the National Hurricane Center predicted, landfall was catastrophic: While officials are still counting the toll, both in terms of lives lost and property destroyed, at least 67 people were killed in Jamaica, Cuba, Haiti and the Dominican Republic. AccuWeather estimates damage at $50 billion.
Even before the storm hit Jamaica and continued north, scientists explained how Climate change helped turn the hurricane into an exceptional Category 5 storm with winds of 185 mph: the warm waters it used for fuel became 900 times more likely due to global warming, which helped increase wind speeds by 10 mph.
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Today, the World Weather Attribution research group summarized the figures for your own reportsimilarly found that human-caused warming increased the tropical cyclone's maximum wind speed by 11 mph—a seemingly small amount that could actually increase damage exponentially—and the amount of extreme precipitation by 16 percent. Overall, this climate shift increased the likelihood of such conditions by about six times. “This study showed that every aspect of this event was amplified by climate change, and that we will see more of the same as we continue to burn fossil fuels,” said Ben Clark, co-author of the report and a research fellow at Imperial College London, during a press conference on Wednesday.
To harvest such power, three main ingredients are required. First, these storms love moisture because dry air prevents them from forming. Second, they need an atmosphere in which there is no vertical wind shear or winds moving at different speeds and directions at different altitudes. And finally, they need warm ocean water to transfer energy from the sea to the sky.
Melissa not only traversed exceptionally hot waters, but also crawled through them at relatively slow speeds, 1 to 3 mph, “allowing the storm to gather enormous destructive energy,” the report notes. The ocean was also temperate deep below the surface, so when a hurricane churned the sea, it pulled out more fuel. (Colder conditions at depth lead to upwells, which reduce the amount of fuel available. In this case, you can actually see the path of cooler water left by the storm – a sort of snail's trail – like Hurricane Erin last year.)
What happened in the Caribbean a few days before landfall stunned scientists. A hurricane “rapidly intensifies” when its maximum sustained wind speed increases by at least 35 mph in a day, and it experiences “extremely rapid intensification” when it reaches 58 mph during that time. Melissa passed this threshold, doubling from 70 mph to 140 mph in just 18 hours. Indeed, studies have shown that Atlantic hurricanes are now twice as likely to intensify rapidly, and scientists have found an explosive increase in these events close to shore. This phenomenon is especially dangerous because local authorities may be preparing for a tamer tropical cyclone and then face something much more destructive.
While some infrastructure could survive the winds, there was no way to avoid another consequence of these storms: storm surge making landfall. This raised the water level in Jamaica by 16 feet. destructive coastal communities. Here, climate change is also exacerbating the situation, as such a flood is layered on top of already higher sea levels. In addition, warmer waters take up more space than colder ones, which is known as thermal expansion.
The precipitation was also catastrophic. The milder the atmosphere becomes, the more moisture it can hold, which is partly why there are fewer extreme precipitation events around the world. Plus, the faster a hurricane's winds blow (and Melissa hit 185 mph again, which is about as fast as they go), the more water it can squeeze out of the sky. Indeed, the report notes that heavy five-day rain events in Jamaica like the one associated with Melissa are about 30 percent more intense and twice as likely in today's climate. For eastern Cuba, the increase is more than 50 percent.
The landscape itself made matters worse, as Melissa's heavy rains flowed down the mountains and valleys, accelerating under their own weight. To make matters worse, it rained in Jamaica before the hurricane arrived, so the Earth could not absorb more water to prevent flooding. “The slow movement of the storm meant that destructive conditions persisted for many hours, with heavy rainfall, hurricane-force winds and storm surge continuing for long periods of time,” Jayaka Campbell, a co-author of the report and a climate scientist at the University of the West Indies in Jamaica, said during a news conference.
However, thanks to advances in hurricane science, forecasters were able to accurately predict Melissa's rapid intensification. giving everyone a lot of attention. This allowed Jamaica to open 881 shelters and pre-position supplies, while Cuba evacuated 735,000 people from coastal and low-lying areas.
“If there's a silver lining to the storm, it's that we're in a time where we have good hurricane forecasts,” Roop Singh, director of city and attribution programs for the Red Cross Red Crescent Climate Center and co-author of the report, said during the call. “This likely saved many lives. At the same time, it is important to note that people do not have living memories of such a severe storm, making it difficult to adequately prepare.”
