The story is now unfolding in the Atlantic Ocean. Hurricane Melissa has strengthened into an extremely dangerous Category 5 storm with maximum sustained winds of 175 mph and will make landfall in Jamaica this evening before heading toward Cuba. This is only the second time in recorded history that an Atlantic hurricane season has produced three hurricanes of this category. Melissa has already killed minimum three people in Haiti and another in the Dominican Republic.
Threats to Jamaica will come from all sides. The island could see up to 30 inches of rain as the storm squeezes moisture from the sky like a huge atmospheric sponge, potentially causing “catastrophic flash floods and multiple landslides”, According to the National Hurricane Center. Melissa will also bulldoze a storm surge of up to 13 feet ashore—essentially a wall of water that will further inundate coastal areas. “No one living there has ever experienced anything like what is about to happen.” writes Brian McNoldy, a hurricane specialist at the University of Miami.
It will take some time for scientists to determine exactly how much climate change affected Melissa, but they can already tell that the storm was fueled by warm ocean temperatures that amounted to 800 times more likely global warming. Here's how climate change is worsening tropical cyclones in general: The hotter the ocean gets (the seas have absorbed 90 percent of the extra heat humans pumped into the atmosphere), the more energy can go into a storm. “The role that climate change played in making Hurricane Melissa incredibly dangerous is undeniable,” Mark Alessi, a research fellow at the Union of Concerned Scientists, said in a statement.
Scientists have already estimated that climate change has increased wind speeds in Melissa by 10 mph, which in turn has increased potential damage by 50 percent. “We now live in a world where human-caused climate change has altered the environment in which these storms are growing and intensifying,” said Daniel Guilford, a climate scientist at the research group Climate Central. “Increasing atmospheric temperatures will increase the amount of moisture in the atmosphere, which will allow Melissa to shed rain more efficiently and effectively over the Caribbean Sea and could cause more flooding than would otherwise occur.”
What makes Melissa particularly dangerous is the fact that it has undergone rapid intensification, defined as a jump in sustained wind speeds of at least 35 mph in a day. doubling the speed from 70 to 140 mph in less than 24 hours. That makes a hurricane even more deadly, not only because stronger winds cause more damage, but also because it can complicate disaster preparations—officials might be preparing for a weaker hurricane but suddenly find themselves faced with an even stronger one. Research has shown huge increase due to rising ocean temperatures, particularly Atlantic hurricanes. twice as likely will now intensify quickly.
At the same time, hurricanes could cause more rainfall as the planet warms. First, for every degree Celsius of warming, the atmosphere can hold 7 percent more moisture. And secondly, the faster the wind speed, the more water a hurricane can squeeze out, like spinning a wet mop. Accordingly, hurricanes can now produce 50 percent more rainfall due to climate change. “A stronger hurricane has stronger updrafts and downdrafts, and the efficiency with which a hurricane can rain largely depends on how intense the storm is,” Guilford said. To make matters worse, Melissa is a fairly slow-moving storm, so it will linger over Jamaica, flooding the island and buffeting it with winds.
When Melissa dumps rain from above, its winds push even more water ashore as a storm surge. Coastlines in the Caribbean have already experienced significant sea level rise, meaning sea levels are already higher than before. (Warmer oceans have an additional effect here because hotter water takes up more space, a phenomenon known as thermal expansion.) All this means is that the base water level is already higher and will be superimposed by the storm surge. “Even small, gradual, subtle changes in sea level can really make a big difference,” Guilford said.
Jamaica faces additional challenges due to its mountainous terrain. Although water accumulates on flat ground, it behaves much more unpredictably on a downhill slope as it easily picks up speed. “When you get a storm like this that's approaching the higher levels of what we've seen, it's harrowing, especially because it's targeting a populated island with a challenging landscape,” said Kim Wood, an atmospheric scientist at the University of Arizona. “You're dealing with a funnel effect where that water, as it falls, will then join other water flowing down the mountainside and compound the impact.”
Perhaps the only good news is that the National Hurricane Center was able to accurately predict that Melissa would rapidly intensify. And overall, scientists are getting even better at identifying why climate change is causing more hurricanes, so they can provide even more accurate warnings to places like Jamaica. But this requires continued government support for this kind of work, while the Trump administration reduced scientific budgets and jobs. “We couldn't do this without continued investment in an enterprise that supports advances not only in science, but in forecasting and disseminating the results of those forecasts,” Wood said.
