Climate change has made two characteristics of Hurricane Melissa more likely: abundance of rain and slowness of destruction.
In Jamaica, the damage from Hurricane Melissa begins to be counted, which made landfall on the island on October 28 with winds of up to 300 km per hour, lightning and torrential rain. And while the tropical cyclone – downgraded by two categories, but still destructive – hits Cuba, the first explanations arrive on what made Melissa the worst storm in the last 174 years of Jamaican history, as well as one of the worst Atlantic hurricanes ever.
According to experts, two factors in particular contributed to the ferocious intensity of the hurricane, and both have to do with the climate crisis.
Record ocean temperatures
Behind the rapid intensification of Hurricane Melissa (which became faster than 110 km per hour in just 24 hours, between 25 and 26 October) there would be the exceptionally high temperature of the waters in the central part of the Caribbean Sea, which in these days is 1.4°C higher than the typical values for the month of October.
Warmer waters inject more energy into storms, and these anomalous temperatures, extending to great depths, provided Hurricane Melissa with a significant amount of extra heat energy. Heat influences the speed of hurricane winds, and the rapid intensification of hurricanes makes it more difficult to predict when and with what intensity they will make landfall.
According to the non-profit organization Climate Centralthese conditions, made up to 700 times more likely by climate change caused by our harmful emissions, would have increased Melissa’s maximum wind speed by about 10 miles per hour, and increased its potential damage by as much as 50%.
A greater humidity load
Warmer sea waters also mean greater availability of rain for the hurricane to discharge. The warmer the sea surface, the more water vapor the storm sucks in as it passes over the ocean. Under these conditions, the storm system strengthens, gathering more and more moisture and transforming into a superstorm. According to Daniel Gilford, a scientist at Climate Central, an increase in precipitation of between 25 and 50% in a storm like Melissa would be attributable to human-caused climate change.
Stagnant hurricane
Finally, the question of Melissa’s slowness remains. Usually, as explained last year in research by Jill Trepanier, an expert in hurricane climatology at Louisiana State University (USA), these stagnant and stationary storms form in October near the Caribbean coasts, but quickly self-extinguish because they end up raising cold water from the depths of the ocean, and because they are disturbed by the wave and descending winds of the atmosphere.
In the case of Melissa this did not happen, because very warm and deep waters caused the hurricane to intensify exactly where it should have died out.
These types of slow, destructive storms are said to be on the rise, perhaps due to Arctic amplification, the narrowing of the temperature difference between Earth’s low and high latitudes caused by global warming. This weakens the winds that normally move storms over the sea, pushing them like corks in a stream. But it is a hypothesis that will need to be consolidated.
