With the torrential rains of Hurricane Harvey, the historic winds of Irma, and Jose still meandering slowly through the Caribbean, the last few weeks have been full of powerful and frequent hurricanes. If the 2017 hurricane season continues like this, it could join 2005 and 2010 as one of the most intense hurricane seasons in recorded history.
Scientists say climate change has probably played a role in shaping this year’s big storms and those previous monster seasons. When scientists build models of the climate system — digital worlds where the physics of a warming atmosphere can spin out thousands of possible futures — they see a clear connection between a hotter planet and hurricanes. In those model Earths, a warmer world makes storms stronger and increases the rainfall they leave behind. In the real world, the planet has gotten warmer, the oceans have gotten warmer, and here we have these intense storms — it all seems to add up.
But, frustratingly, it’s harder to look at the actual hurricanes that have happened and find evidence of those changes playing out the way we’d expect. The planet’s average global temperature has increased, but its hurricanes don’t seem to have changed much. We can tie hurricanes to climate change in theory, but we don’t see a statistical signal of those theories playing out in practice. It could be that the climate hasn’t changed enough yet. It could be that hurricanes have changed, just not in a way that’s apparent statistically. We can’t be sure.
What would it take to change that? Is there data we don’t have now that could make the connections between climate change and hurricanes more explicit? I asked several scientists who study these issues about the data they wish they had. They told me that the hole in our present understanding is tied to a lack of knowledge about what happened in the past. We don’t know if climate change is altering hurricanes now, because we know very little about what hurricanes were doing 100 years ago.
We’re not lacking a historical record of hurricanes. We’re just lacking a complete one. The Atlantic Hurricane Database goes back to 1851, and this raw data suggests that the number and intensity of Atlantic hurricanes has significantly increased over time, and that the increase is correlated with rising surface water temperature. But there’s a catch, said Thomas Knutson, leader of the climate impacts and extremes research team at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory.