Climate crisis made 2020 Atlantic hurricanes as much as 11% wetter, study finds

The record-breaking 2020 Atlantic hurricane season was made wetter by the climate crisis.

That’s the conclusion of a first-of-its-kind study published in Nature Communications. Past studies have both predicted that the climate crisis would lead to wetter tropical storms and shown that this was in fact the case for particularly devastating hurricanes like Katrina or Maria. However, this study is notable because it considers the impact of global warming on an entire season, which means it is not biased by focusing only on the most destructive storms.

“What this work shows us is that even a storm, maybe it’s a tropical storm that only dumped a couple of inches of rainfall in a given region… has still been impacted by climate change,” study lead author and Stony Brook University atmospheric scientist Kevin Reed told The Washington Post.. “As far as we know, this is kind of the first study to objectively apply an attribution framework regardless of intensity.”

To assess the impact of the climate crisis on the 2020 hurricane season, the research team used a computer simulation, AP News explained. The researchers first looked at how much precipitation the season generated and then compared it to a world without human-induced global warming.

Between 1850 and 2020, the burning of fossil fuels has increased average global surface temperatures by an average of more than one degree Celsius, the study authors explained. This in turn meant that sea-surface temperatures in the North Atlantic basin were 0.4 to 0.9 degrees Celsius warmer during the 2020 hurricane season than they would have been otherwise.

The researchers found that this had a real impact on rainfall. All of the 2020 storms that reached tropical storm strength had extreme three-hour rainfall rates that were 10 percent higher than they would have been without the climate crisis and extreme three-day rainfall amounts that were five percent higher. For just the hurricanes, extreme three-hour rainfall rates went up by 11 percent while extreme-three day totals rose by eight percent.

“It doesn’t sound like a lot, but if you’re near a threshold, a little bit can push you over the top,” Lawrence Berkeley National Lab climate scientist and study co-author Michael Wehner told AP News. “The implication is that that means there was more freshwater flooding and that the damages from freshwater flooding were increased, but by how much would require a more detailed analysis.”

What is clear is that the 2020 Atlantic hurricane season did plenty of damage. It had a total of 30 named storms, making it the most active hurricane season on record. It also broke the record for the most storms to reach the U.S. coastline. The season caused more than $40 billion in damage, The Washington Post reported, and part of what made it so dangerous was flooding. Rainfall from Hurricane Eta killed 100 people in Central America and caused a landslide that barrelled into a village. Flooding from Hurricane Laura in the Gulf Coast claimed multiple lives.

In general, the climate crisis leads to more extreme rainfall events because warmer air can hold more moisture. The study is more evidence that the planet is already facing the consequences of global warming.

“It isn’t this end-of-the-century problem that we have to figure out if we can mitigate or adapt to,” Reed said, as The New York Times reported. “It is impacting our weather and our extreme weather now.”