The story currently takes place in the Atlantic Ocean. Hurricane Melissa has strengthened into an extremely dangerous Category 5 storm with maximum sustained winds of 175 mph, and is expected to hit Jamaica this evening before heading toward Cuba. This is only the second time in history that an Atlantic hurricane season has produced three hurricanes of this category. Melissa has already killed at least three people in Haiti and another in the Dominican Republic.
Threats against Jamaica will come from all sides. The island could see up to 30 inches of rain as the storm extracts moisture from the sky like a massive atmospheric sponge, potentially causing “catastrophic flash flooding and numerous landslides,” according to the National Hurricane Center. Melissa will also bulldoze a storm surge of up to 13 feet – essentially a wall of water that will further flood coastal areas. “No one living there has ever experienced anything like what is about to happen,” writes Brian McNoldy, a hurricane expert at the University of Miami.
It will take scientists some time to determine exactly how much climate change supercharged Melissa, but they can already say that the storm fed on warm ocean temperatures, which are 800 times more likely because of global warming. This is how climate change is making these tropical cyclones overall worse: The warmer the ocean becomes – the seas have absorbed 90 percent of the extra heat that humans have pumped into the atmosphere – the more energy can be transferred into a storm. “The role that climate change played in making Hurricane Melissa incredibly dangerous is undeniable,” Marc Alessi, a climate attribution scientist at the Union of Concerned Scientists, said in a statement.
Scientists can already estimate that climate change has increased Melissa’s wind speed by 10 mph, increasing potential damage by 50 percent. “We currently live in a world where human-caused climate change has altered the environment in which these hurricanes develop and intensify,” said Daniel Gilford, a climate scientist at the research group Climate Central. “Rising atmospheric temperatures increase the amount of moisture in the atmosphere, which will allow Melissa to rain more effectively on the Caribbean and could cause more flooding than would otherwise have occurred.”
What makes Melissa even more dangerous is the fact that it experienced rapid intensification, defined as an increase in sustained wind speed of at least 35 mph in one day, having doubled its speed from 70 to 140 mph in less than 24 hours. This makes a hurricane all the more deadly, not only because stronger winds cause more damage, but also because it can complicate disaster preparations: Authorities might prepare for a weaker storm, only to face a much worse one. Research has shown a dramatic increase in the number of rapid intensification events near coasts, thanks to rising ocean temperatures, with Atlantic hurricanes now twice as likely to intensify rapidly.
At the same time, hurricanes are capable of producing more precipitation as the planet warms. On the one hand, the atmosphere can contain 7% more humidity per degree Celsius of warming. And second, the faster the wind blows, the more water a hurricane can wring out, like wringing out a wet mop. As a result, hurricanes can now produce 50 percent more precipitation due to climate change. “A more intense hurricane has stronger updrafts and downdrafts, and how effectively the storm can rain depends critically on the intensity of the storm,” Gilford said. Worse yet, Melissa is a rather slow-moving storm, so it will linger over Jamaica, flooding the island and buffeting it with the winds.
As Melissa causes rain to fall from above, her winds will push even more water onto the shore as a storm surge. Caribbean coasts have already experienced significant sea level rise, meaning levels are already higher than before. (Warmer oceans have an additional effect here, because warmer water takes up more space, a phenomenon known as thermal expansion.) All this means that base water levels are already higher, upon which storm surge will build. “Small, incremental, marginal changes in sea level can really lead to intense changes,” Gilford said.
Jamaica faces an additional challenge due to its mountainous terrain. While water collects on flat ground, it behaves much more unpredictably when it flows down a slope because it easily gains momentum. “When you have a storm like this that’s approaching the upper echelons of what we’ve seen, it’s heartbreaking, especially because it’s pointing toward a populated island with complex terrain,” said Kim Wood, an atmospheric scientist at the University of Arizona. “You’re dealing with a funneling effect, where this water, as it falls, will then join other waters that are coming down the mountainside and exacerbate the impacts.”
Perhaps the only good news here is that the National Hurricane Center was able to accurately predict that Melissa would rapidly intensify. And generally speaking, scientists are getting better at determining how climate change amplifies hurricanes, so they can provide ever more accurate warnings to places like Jamaica. But that requires continued government support for this type of work, as the Trump administration has cut science budgets and jobs. “We could not achieve this without continued investment in the business that supports not only scientific advancements, but also forecasting and reporting the results of those forecasts,” Wood said.
