Not all scientists are ready to point the finger at climate change, though. Some say both Harvey’s and Irma’s devastation, coming during the peak of hurricane season, would have happened regardless.
Miami, Florida, for example, is low-lying and one of the country’s most vulnerable spots for hurricanes. In addition, South Florida’s infrastructure isn’t fully equipped to deal with recent construction and population growth. More than 6 million people have moved to the state since 1990.
“There is a constant battle between our ability to prepare for hurricanes and the pressure for urban expansion,” says Jean-Pierre Bardet, an engineering professor at the University of Miami.
Houston, too, is at high risk for hurricanes, scientists say. The low-lying coastal city is on the Gulf of Mexico, one of the most common spots for hurricanes to form. The city has struggled with flooding on and off for more than a century.
As Houston grew rapidly over the past two decades, flooding only got worse. Some developers built entire neighborhoods next to or even inside floodplains—the areas most likely to end up underwater.
As the city expanded, it also added about 25 percent more pavement, cutting back on prairies and wetlands around the city. Unlike soil, roads and parking lots do not absorb water, making the effects of excess rainfall even worse.
Those conditions made an event like Harvey almost inevitable, say Suzana Camargo and Adam Sobel, science professors at Columbia University.
“Given a metro area of 6.5 million people that basically sits in a paved floodplain, crossed by bayous, creeks, and rivers, and the same [weather] situation, we would be seeing a very major disaster even without any human influence on climate,” the professors wrote in Fortune magazine.