PARIS ― There’s a bit of an apocalyptic vibe in the air. Even though it’s tropical storm season, it has been alarming to watch hurricanes Harvey and Irma strike land in rapid succession. Now José, a Category 4 storm, and Katia, a Category 3 storm, are not far behind.
Harvey created unprecedented flooding in Texas, and Irma is the most powerful tropical cyclone ever to take shape in the Atlantic Ocean. The French island of St. Martin has been 95 percent destroyed, according to local officials, and at least four people have died. The devastation has led many to wonder what role climate change may be playing in these powerful storms.
Some political leaders are drawing a clear link between the two, such as Paris Mayor Anne Hidalgo, who declared on Thursday that Irma is a “concrete manifestation” of global warming. A few hours later, French President Emmanuel Macron said it was necessary to look at the “deep causes behind these types of events.”
But the connection between climate change and hurricanes is complicated, with several separate questions to consider. Is climate change causing more hurricanes (also called typhoons and cyclones, depending on where they originate)? Are the storms more powerful? Are they more destructive? And what does this portend for the future?
To see what science has to say, HuffPost France interviewed Robert Vautard, a climatologist with France’s National Center for Scientific Research who specializes in the relationship between extreme events and climate change.
Will storms increase in number or danger?
Researchers create mathematical models to test the ways that greenhouse gas emissions could evolve and to simulate the warming that could take place in the oceans and atmosphere. The models allow them to extrapolate how different weather phenomena, such as hurricanes, may develop in the future under varying temperature scenarios.
But so far, it’s hard for the models to predict how rising temperatures will specifically affect storms. “The results lean toward a lessening in terms of the number of tropical storms and an increase in terms of wind force,” Vautard said. “But there are a lot of uncertainties.”
To be clear, the models are able to predict global climate scenarios with a high degree of accuracy. But predicting the evolution of storms requires even more precision, since they are only tiny events compared to the overall scale of the planet. Although there seem to be some consistencies in the storm models, their predictions can’t be relied upon at this point.
How about greater damage?
Vautard and other scientists largely agree on one effect of climate change, however. “The impact tropical storms have is going to increase, because the atmosphere is going to warm up and will therefore contain more water,” he said. “Which means more rain.”
And more rain means more flooding, which can be just as damaging as a hurricane’s strong winds, as Harvey demonstrated.
Another certainty is that climate change is causing sea levels to rise, which means greater storm surges and higher waves when a storm hits the coast.
“Knowing these two things, it’s safe to say that hurricanes affecting low-elevation islands will therefore cause greater damage, even if they have the same features as today’s do,” said Vautard.
In short, even if scientists aren’t sure about the number and potency of future tropical storms, they are fairly certain these storms will cause more damage if nothing is done to keep climate change in check.
Is climate change to blame for Harvey and Irma?
Harvey caused historic flooding in Texas. Is this proof that global warming is already making hurricanes worse? The United Nations’ World Meteorological Organization and some American climatologists say it is, absolutely. But Vautard doesn’t want to be that assertive.
“It’s too early to say. Worldwide, you could say that global warming has definitely caused an increase in rainfall, but in terms of Hurricane Harvey in particular, we’ll have to wait on the studies being done right now,” he said.
Climate science is much more about examining what happens on a global multiyear average scale ― not about specific events. Researchers will be studying Harvey and looking at how it fits into broader trends, Vautard said.
As far as tropical storms are concerned, it’s also difficult to know what the historic trends have been. “Since they mostly happen at sea, you need satellite data to get statistics about hurricanes,” said Vautard. But that type of data has only been around for about 40 years, which is not long enough to establish reliable scientific models.
Going forward, researchers will continue to improve the precision of their models, which will allow them to better understand how and why hurricanes form, and how climate factors contribute to that. “We aren’t far off,” Vautard said.