Contrary to recent rumor, the U.S. government cannot direct major hurricanes like Helene and Milton toward red states. According to two new rapid attribution studies by World Weather Attribution and Climate Central, however, human actors almost certainly made the storms a lot worse through the burning of fossil fuels.
A storm like Hurricane Helene, which has killed at least 227 people so far and caused close to $50 billion in estimated property losses across the southeast, is about two-and-a-half times more likely in the region today compared to what would be expected in a “cooler pre-industrial climate,” WWA found. That means Helene, the kind of storm one would expect to see once every 130 years on average, is now expected to develop at a rate of about once every 53 years. Additionally, WWA researchers determined that extreme rainfall from Helene was 70% more likely and 10% heavier in the Appalachians and about 40% more likely in the southern Appalachian region, where many of the deaths occurred, due to climate change.
“Americans shouldn’t have to fear hurricanes more violent than Helene — we have all the knowledge and technology needed to lower demand and replace oil, gas, and coal with renewable energy,” Friederike Otto, the lead of WWA and a senior lecturer in climate science at Imperial College London, said in a statement. “But vitally, we need the political will.” Alarmingly, the attribution study found that storms could drop an additional 10% or more rain on average as soon as the 2050s if warming reaches 2 degrees Celsius.
WWA’s study is not the first to be released on Hurricane Helene, but it was still produced incredibly quickly and has not been peer reviewed. Just a few weeks ago, the group issued a correction on a report estimating the contribution of climate change to recent flooding in Europe.
Separately, Climate Central looked at Hurricane Milton, which already has the distinction of being the fifth strongest Atlantic storm on record. The nonprofit’s findings show that Milton’s rapid intensification — one of the fastest and most powerful instances of the phenomenon in history — is primarily due to high sea surface temperatures in the weeks before Milton developed, which was made at least 400 times more likely by climate change and up to 800 times more likely. (WWA relied on Climate Central’s Climate Shift Index for oceans for its research, but found “climate change made the unusually hot sea surface temperature about 200-500 times more likely.”)
Attribution science is incredibly tricky, especially for a storm system like a hurricane that has variables ranging from wind shear to the El Niño–Southern Oscillation to ocean temperatures and jet stream variations. When I spoke to a member of the WWA team earlier this year, I was told the organization specifically avoids attributing the intensification of any individual hurricane — in theory, one of the more straightforward relationships — to climate change because of the relatively limited historical modeling available. Even something like rainfall “is not necessarily correlated to the magnitude of the floods that you see because there are other factors,” WWA’s Clair Barnes previously told me — for example, the steep-sided mountains and hollows of western North Carolina, which served as funnels for rainfall to an especially devastating effect.
But regarding the relationship between hurricanes and climate change more generally, “We’re relatively confident that storms will get more intense” in a warming world, Gabriel Vecchi, a Princeton geoscientist, explained on a recent episode of Heatmap’s Shift Key podcast. “And we’re really confident that storms will get wetter.”
Helene and Milton hammer that point home: once-in-a-generation storms can now arrive on back-to-back weekends. You can almost understand the impulse to devise a zany explanation as to why. Only, the truth is far simpler than cloud seeding or space lasers: a warmer atmosphere makes for warmer oceans, which make for wetter, more intense storms. And while hurricane seasons eventually end, global temperatures haven’t stopped going up. That, perhaps, is the more terrifying subtext of the attribution studies: There will be more Miltons and Helenes.
