Hurricanes, wildfires and other natural disasters seem to be getting more severe. Here’s how they may be linked with climate change.
One of the most destructive fire seasons in California history keeps getting worse, with three wildfires driven by Santa Ana winds burning brush and homes in the Southland. At the other extreme, four hurricanes — Harvey, Irma, Maria and Nate — have made landfall in the U. S. this year, the first time in more than a decade that so many have done so.
Extreme events have been hitting the country from all sides. To what extent does climate change influence them?
Here are a few ways researchers think that climate change’s effects could play out.
“Fires tend to be associated with hotter drier weather, everything else being equal,” said Benjamin Bond-Lamberty, an ecosystem ecologist with the Joint Global Change Research Institute, a collaboration between the Pacific Northwest National Laboratory and the University of Maryland in College Park. That’s assuming, of course, that you have an ignition source and more tinder to burn.
A 2013 study in PNAS found that the risk of a Hurricane Katrina-level storm surge rose two to seven times for every 1.8-degree Fahrenheit increase in temperature.
“We think that Harvey type of rainfalls will become noticeably more frequent as the century goes on,” said Kerry Emanuel, an atmospheric scientist at MIT.
For hurricanes, that can be really dangerous, given the deaths and damage caused by rain and storm-surge flooding, Emanuel said.
“Water is the big killer in hurricanes, not wind,” Emanuel said. “Wind gets everyone’s attention, but it’s water that kills, and it’s often water that does most of the damage.”
“We do think the incidence of the high-intensity events is going up, and that’s sort of what matters for society,” Emanuel said. “Those are the destructive ones.”
California is no stranger to drought. But because the multi-year weather cycles known as El Niño and La Niña tend to scramble the overall trend a little, it’s a challenge to tease out certain direct connections between droughts and climate change, scientists say. However, there are a few connections researchers can draw.
Even if total rainfall stays the same, higher temperatures will probably drive down the average moisture level in the soil, leaving less water available for living things.
“This large-scale feature… in the Pacific Ocean is one of the important factors why a lot of climate models, when they project into the future, most of them show drying in the southwestern United States,” Leung said.
As a rule, climate scientists are generally loathe to say that any particular fire, flood, drought or hurricane was caused by climate change — but they can point to the general likelihood that such extreme events might occur, or the complex ways in which they’re influenced, by climate change.
The bright side of all this extreme weather? The more that extreme events occur, the more that scientists have to study — and the better they will be able to nail those relationships down in the future.
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