A new study suggests that, by the end of the century, "Katrina-like extreme events" could become as much as 10 times as commonplace due to changes caused by global warming.
Using more than 10 different climate change predictor models, Aslak Grinsted, a climate scientist with Denmark's Centre for Ice and Climate, says that the world has seen a "significant positive trend" of strong hurricanes, and that the trend is likely to continue as global temperatures increase.
"It's not great that there are going to be more disasters," he says. "But it's comforting to me as a scientist that all the models agree about this."
Though climate scientists have long contended that climate change has led to more extreme and common hurricanes, they have been reticent to blame any single hurricane on climate change. Grinsted says that's still the case—there have been hurricanes the size of Katrina roughly once every 20 years since 1923—but it's reached the point where any given hurricane is more likely caused by climate change than not.
"Whenever we're asked whether Katrina or Sandy was caused by global warming, we have to give the standard answer that no single event can be attributed to warming," he says. "Well now, the odds have changed sufficiently and it's misleading to people to trot out the standard answer."
According to his research, "we have probably crossed the threshold where Katrina magnitude hurricane surges are more likely caused by global warming than not."
Grinsted wrote a study published in September that used historical data to prove that hurricanes were more severe and more common in years that the Atlantic Ocean was warmest. He says his latest study is a "companion piece" to that study. His predictions are based on projected ocean warming temperatures, not predicted sea level rise, which the U.N. Intergovernmental Panel on Climate Change says could be as much as two feet worldwide by the year 2100.
"We're taking out the effect of the tides and the effects of sea level rise," he says. "Given those, this is effect is likely to be even more extreme."
Though there are likely to be more hurricanes, Grinsted says that not every hurricane that is as strong as Katrina will have the same devastating effects.
"Katrina was such a disaster because New Orleans wasn't prepared," he says. "This shows we have to adapt our coastal infrastructures to be able to deal with extremes."