Hurricane Irma struck the Caribbean last night (Sept. 6), killing at least ten people and causing thousands of dollars in infrastructure damage on affected islands. It’s the strongest storm ever recorded in the Atlantic, and it comes just a week after Hurricane Harvey ravaged the southeastern US. On its tail are two newly-minted hurricanes, Jose and Katia.
The waning summer months in the Northern Hemisphere are peak hurricane season because the tropical ocean waters close to the equator become warmer with the summer. The warm, humid air rises, then condenses and cools and dumps rain below. Air pressure gradients between the warm and cool air keep the cycle going.
These wind patterns can lead to tropical storms, but not all tropical storms grow into hurricanes. This is because the same gusts of wind end up disturbing the top layer of warm water too much, and bring up colder waters from below. The cold water starves the system for energy, and the storm fizzles out.
But as New Scientist points out, if these developing storms only surface more warm water, they keep fueling themselves. Irma, a so-called “Cape Verde storm,” began west of Africa. Surface temperatures were more than 1°C (1.8°F) warmer than usual, which means that the water hundreds of feet below the surface were hot enough to keep feeding the beast all the way across the Atlantic Ocean.
Our fossil-fuel consumption undoubtedly helped set the stage for Irma to become as big as it did. “Burning coal, oil and gas warms our planet and that way supplies energy for the build-up of ever more powerful tropical storms,” Anders Levermann, a climate scientist at the Potsdam Institute for Climate Impact Research, told Bloomberg.
Not everyone acknowledges that humans have contributed to these super storms. Rush Limbaugh, a conservative pundit, denied this week that human activity had anything to do with Irma, or climate change more broadly. “In the official meteorological circles, you have an abundance of people who believe that man-made climate change is real,” he said on his radio show. “And they believe that Al Gore is correct when he has written—and he couldn’t be more wrong—that climate change is creating more hurricanes and stronger hurricanes.”
But Limbaugh and other climate change deniers are falling farther outside the mainstream. Even Fox News, a right-leaning news outlet that frequently features Limbaugh as a guest, had a hard time denying anthropogenic global warming’s effect on the storm. On Sept. 6, they addressed the issue, however begrudgingly:
Scientists take weeks or months to conduct intricate studies, using computer simulations, to see if a storm was worsened by man-made climate change. There have been a limited number of hurricanes since record-keeping began in 1851, which makes it difficult to do robust statistical analyses. However, scientists have long said future global warming would make some of the worst storms stronger and wetter and recently have linked climate change to future rapid intensification of storms. There’s been scientific debate over whether global warming means more storms, but the stronger and wetter [sic] is generally accepted by scientists.
Although Fox News’s acknowledgement doesn’t accept all of the proven science around climate change, its willingness to state that global warming has most likely contributed to Irma is meaningful in today’s politicized media environment.
Irma destroyed large swaths of the buildings on some of the Caribbean islands, including St. Martin and Barbuda, before brushing the northern coast of Puerto Rico on Wednesday night, leaving 1 million residents without power. Right now, the hurricane is expected to hit parts of Cuba, the Dominican Republic, Haiti, the Bahamas, and Turks & Caicos today and tomorrow. Projections have Irma making landfall in Florida after that, though that could change; forecasters at the National Hurricane Center are constantly updating their models to track the storm’s progress.