This summer, the US has had several record-smashing natural disasters: over 110 large fires are burning throughout the country, especially in the West; California recently had a deadly heat wave that set all-time heat records in several towns, including San Francisco; and after Hurricane Harvey brought unprecedented raining and flooding to Texas, Hurricane Irma swept through the Caribbean and Florida — the strongest storm ever recorded in the Atlantic Ocean outside of the Caribbean and the Gulf of Mexico.
Although it’s impossible to attribute any one of these single events to climate change, the signals are clear, scientists say. (That kind of attribution may be possible with certain kinds of modeling studies; those studies have not yet been conducted.) These extreme weather events are very consistent with what climate change is expected to bring in the years ahead: global weirding. Extreme weather events become more extreme, and climate change is “‘loading the dice’ toward more extreme floods, heat waves, droughts and hurricanes,” says Michael Mann, a climatologist and director of the Earth System Science Center at Pennsylvania State University, in an email to The Verge. “We shouldn’t be surprised we’re turning up snake eyes so often now.”
Mann’s not alone in thinking this summer has the shape of things to come. “This is going to be the future,” says David Titley, a meteorologist and director of the Center for Solutions to Weather and Climate Risk at Penn State. The future is going to have stronger heat waves, more wildfires, heavier rain storms, and a greater number of very intense hurricanes, Titley says. “At some point, our luck will run out.”
It’s wrong to say that climate change caused this summer’s extreme weather events, scientists say. Hurricanes and fires have occurred in the past, after all. But “undoubtedly climate change is playing a role,” says Kevin Trenberth, a distinguished senior scientist at the National Center for Atmospheric Research. These extreme weather events “are being exacerbated by the climate change element.”
So here’s the role climate change might have played in this summer’s record-breaking heat waves, wildfires, and hurricanes.
Over Labor Day weekend, California was broiled by a record-setting heat wave that killed six people. San Francisco reached 106 degrees Fahrenheit, the hottest it’s ever been since record keeping started about 150 years ago. (The previous record was 103 degrees Fahrenheit, set in 2000.) A few other cities broke heat records, as well. In June, Phoenix, Arizona, also hit a daily record, reaching 119 degrees Fahrenheit.
Heat waves are the simplest weather event to attribute to climate change, says Adam Sobel, an atmospheric scientist at Lamont-Doherty Earth Observatory and head of Columbia University’s Initiative on Extreme Weather and Climate. A variety of studies have shown that a warming climate increases the chances of heat waves and how severe those heat waves are going to be, Sobel says.
The world’s average temperature has increased roughly by 1.53 degrees Fahrenheit from 1880 to 2012, according to the Intergovernmental Panel on Climate Change. That may not seem like a lot, but if we don’t keep global warming well below 3.6 degrees Fahrenheit, we could see irreversible changes like melting polar ice caps, extensive flooding, bleached coral reefs, food shortages, and deadly diseases. As temperatures rise, there’s a greater chance of getting more intense heat waves and setting new heat records, says Sobel.
All over the US, there are more than 110 large fires, burning through almost 2 million acres of land, including more than 80 wildfires in the western part of the country. These fires are making it hard to breathe all over the Pacific Northwest. “It’s very unusual to have this many fires burning this many acres across such a broad area at this time in September,” National Interagency Fire Center spokeswoman Jennifer Jones told Reuters. So far this year, we’ve had more than 48,000 fires, burning more than 8 million acres of land, 2 million acres over the national yearly average from 2007 to 2016.
There are several ingredients required for wildfires — some connected to climate change and some that have nothing to do with it. But dry conditions and extreme heat create good tinder, making wildfires worse in certain areas, says Benjamin Bond-Lamberty, an ecosystem ecologist with the Joint Global Change Research Institute. A warmer planet will cause more water to evaporate off the landscapes, drying trees and grasses — which then burn more easily. “That sets the stage for increased fire,” Bond-Lamberty says.
Climate change can also make forests more prone to burning, since some pests can spread more readily in warmer temperatures, Bond-Lamberty says. The mountain pine beetle, for instance, is thriving because warmer winters don’t kill its larvae, allowing the beetles to spread and kill more trees, which serve as fuel. “That really sets up a lot of forest ready for things like a wildfire,” he says.
Of course, climate change alone doesn’t cause wildfires — lightning or people are still required. A Forest Service policy of suppressing fires over much of the 20th century has also made our forests older, and more prone to burning. “We’re still paying the cost of that 20th century policy,” Bond-Lamberty says. “There’s a big accumulation of fuel built up on the landscape.”
Still, climate change might already have an effect. A study last year found that in the West, climate change has doubled the area affected by forest fires over the last 30 years. Washington state had its biggest fire in state history in 2015, breaking its 2014 record, says Amy Snover, the director of the University of Washington’s Climate Impacts Group. The fire season has also lengthened, starting a month earlier in Alaska, she writes in an email to The Verge.
This hurricane season has been incredibly active, with a number of severe storms. First, Hurricane Harvey barreled into Texas, dumping record rains and causing unprecedented flooding in cities like Houston. Then, Hurricane Katia struck the east coast of Mexico, and Hurricane Irma — a Category 5 hurricane and one of the strongest storms ever recorded in the Atlantic — wreaked havoc on the Caribbean. (Irma smashed a bunch of other records.) Another hurricane, called Jose, followed Irma, but now it seems the storm may remain out in the ocean.
The intensity of these hurricanes seem to match what climate scientists are expecting in the future, says Titley. Research shows that strong hurricanes, like Harvey and Irma, will become more frequent as the planet warms, says Suzana Camargo, a professor of ocean and climate physics at Lamont-Doherty Earth Observatory at Columbia University.
Climate change is expected to affect hurricanes in a few ways: warmer ocean waters will provide more energy to these storms, and more moisture in the atmosphere will increase the amount of rain these hurricanes can dump. Rising sea levels will also make storm surge from hurricanes worse, leading to higher floods.
Whether climate change is already affecting hurricanes is up for debate, Sobel and Camargo say. It’s true that Harvey was fueled by warmer than usual waters in the Gulf of Mexico, but it was also particularly destructive because it stalled over Texas for a few days, dumping unprecedented amounts of rain. It’s still an open question whether climate change has anything to do with wind patterns, Titley says. And we don’t have enough data on hurricanes to understand whether stronger storms like Harvey and Irma are part of a larger trend, Sobel says.
“The change might be there but it’s hard to prove it,” he says. “It’s like you’re listening to somebody talking quietly in a loud room. You may not be able to hear them but that doesn’t mean they’re not talking.”
Whether we can attribute Harvey and Irma directly to climate change, however, kind of misses the point, Titley says. “People can see that these changes are coming and they are very consistent with what the vast majority of climate scientists have told us for decades is going to happen,” he says. “We shouldn’t really be surprised.”
Climate change is a known threat multiplier: this summer’s extreme weather events are just a taste of what’s about to come — and the sooner we address climate change, the better off we’ll be. That means lowering greenhouse gas emissions and building infrastructure that can survive sea level rise, for instance. “By and large, I think most of us don’t really like the change what we’ve seen,” Titley says, “and the climate system is kind of saying, ‘Hey guys, you ain’t seen nothing yet.’”