Storms and fires caused unprecedented destruction in the United States in 2017. Why?
2017 is about to become the most expensive disaster year in US history, costing nearly $400 billion in damages.
How did that happen? Consider some of the record-breaking weather events that came our way:
As of October, the National Oceanic and Atmospheric Administration had counted 15 disasters with damages topping $1 billion, tying 2017 with 2011 for the most billion-dollar disasters in a year to date. And that was before the California wildfires. (We included some of those fires in the map below):
The unending string of calamities was shocking to many Americans. As Paolo Bacigalupi, who writes climate dystopia fiction, tweeted in August: “The thing that bothers me most about these unprecedented disasters is that even I imagined they wouldn’t happen for a long time yet.”
Yet we must see 2017 as an average year, if not a baseline. We must reckon with the likelihood of even worse storms, heat waves, fires, and droughts as the Earth warms — because scientists expect even this “new normal” to get worse.
The reasons for this are many: As the climate changes, the US is becoming much more vulnerable to disasters. People keep flocking to live in places we know are likely to be hit. And our policies don’t protect them, not by a long shot.
Here are some of the lessons we’ve learned from 2017, and what they suggest for how to prepare for future catastrophes.
Climate scientists have been warning about extreme weather, that it would become more frequent and intense in new ways. Yet 2017 still seemed like a brutal wake-up call to nature’s extraordinary power, and the frightening possibilities of this warmer world.
There’s still a lot we don’t know about why some weather is so extreme and how much climate change is to blame (especially when it comes to hurricanes). But 2017 gave us more clues about what we can expect in the world to come, hints that hopefully will help us prepare for the future.
This is what we understand about the connections between climate change and the disasters we saw this year.
Floods and rain
The year started off with torrential rainfall in California, marking the wettest winter in a century. Parched after years of drought, the rainfall officially brought the dry spell to an end as floods inundated hundreds of homes, landslides buried roads, and high water levels threatened to burst dams. Flooding across Missouri and Arkansas in the spring also claimed 20 lives and carried a $1.7 billion price tag.
Rainfall, both the amount and the rate, represents one of the strongest signals of climate change. Warmer air increases the evaporation rate of water, and for every degree Celsius increase in temperature, a parcel of air can hold 7 percent more water.
Average annual rainfall across the United States has gone up by 5 percent since 1990, though there’s regional variation, according to the National Climate Assessment .
Scientists have found that the amount of rain dished out by heavy rainstorms has gone up 10 percent since 1900 due to global warming. Extreme rainfall events are trending upward, and nine of the top 10 years for extreme one-day precipitation events have happened since 1990.
And all this moisture-laden air helped drive the powerful hurricanes that made landfall in the United States.
“Hurricanes live and die by the amount of rainfall they make out of moisture,” George Huffman, a research meteorologist at NASA Goddard Space Flight Center, told Vox.
Hurricanes
“To say this hurricane season has been historic is an understatement,” FEMA Administrator Brock Long told Congress in October.
Harvey, Irma, and Maria all made landfall as powerful Category 4 storms with winds exceeding 130 mph. Harvey in particular dumped a truly staggering amount of rain over Houston. The estimated 24 trillion gallons that fell there was so heavy it actually depressed the earth more than half an inch in some spots, according to preliminary analysis from the Scripps Institution of Oceanography.
These are the types of storms climate scientists expect to see more of in a warmer world.
First off, yes: There’s consensus that the science of climate change predicts that in a warming world, hurricanes will become more intense, carry more rain, and cause worse coastal flooding linked in part to sea level rise.
But here’s the thing: We don’t yet currently know, conclusively, that the hurricane season as a whole represents a result of climate change. “At this point it’s really uncertain if there’s any detectable human influence on any hurricane or tropical cyclone metric,” Tom Knutson, an NOAA meteorologist who studies hurricanes, told Vox in October.
There’s just not enough data. Meteorologists have only been tracking hurricanes with satellites since the 1970s. It’s possible that historic hurricane records, which go back to the 1800s, are incomplete or have inaccurate information on wind speeds and size. Considering how hurricanes have been lashing against the Atlantic’s coasts for untold epochs, we just have a tiny slice of data to determine what’s “normal.”
While it’s hard to say if the punishing number and intensity of storms were due to climate change, climate scientists have now determined — in two separate research efforts — that Hurricane Harvey’s record-blasting rains (best measured in feet for much of Houston) were likely amplified by climate change.
“Human-induced climate change likely increased Harvey’s total rainfall around Houston by at least 19 percent, with a best estimate of 37 percent,” Michael Wehner, a co-author on an attribution study recently published in Geophysical Research Letters, said at the American Geophysical Union conference in December. And the corresponding study in Environmental Research Letters concluded that climate change increased flooding by around 15 percent.
Even with climate change, Harvey’s rain was an extremely rare event, expected not to return for thousands of years, Karin van der Wiel, a co-author of the Environmental Research Letters study, said. Still, the odds of seeing such an extreme event have changed, she says. “It’s between 1.5 and 5 times more likely now than in pre-industrial times.”
What’s still not known: Did climate change alter the odds of seeing three incredibly strong storms — Harvey, Irma, Maria — in a row this season?
“We tend to look at [hurricanes] one at a time,” Wehner said. “What’s the probability of having three extraordinary events? What’s the probability of having $250 billion in damage one season? That’s a blind spot.”
Heat waves
In June, the Western US experienced the most intense heat wave ever to strike so early in the year, leading to dozens of flight cancellations. On June 21, Ocotillo Wells, California, reported a temperature of 124 degrees Fahrenheit, the hottest reading ever in San Diego County.
Farther north, Olympia, Washington, set a June temperature record of 98 degrees Fahrenheit. The searing heat persisted throughout July in the Pacific Northwest, and was followed by another wave in October, as high temperatures rippled through the Midwest and reached triple digits around Los Angeles, shattering records.
Wildfires
One of the biggest factors in this year’s record wildfire season was, oddly, rainfall.
Vegetation across much of the drought-stricken west eagerly soaked up the surfeit of water from the wet winter, leading to a rapid, vast growth spurt in trees, grasses, and shrubs in the spring. Then summer and fall brought intense heat that dried out these plants, turning the greenery into fuel.
Wildfires began igniting over the summer, sending choking air pollution through Washington, Oregon, Idaho, Montana, and California. Huge new fires appeared in subsequent months, causing record damage, including the ongoing fires around Los Angeles that are poised to burn the rest of the year. The Thomas Fire in Santa Barbara and Ventura counties, at more than 280,000 acres, is the largest fire in California history. Across the United States, more than 9.5 million acres have burned to date, making 2017 the second-worst year for fires in terms of area.
But the wildfires that scorched vast swaths of the US this year can scarcely be described as natural disasters, since human activities exacerbated them at every step.
“The context for this is as much about society living in these very fire-prone environments as it is about the climate,” said Tim Brown, director of NOAA’s Western Regional Climate Center. “One significant difference is we’ve had very significant population growth and urban development here since the 1960s.”
And changes in the climate are making many of these wildfires worse. Researchers found that human-caused climate change accounts for 55 percent of the increase in drying out of Western forests, a major factor in wildfires, and has led to a doubling of the area burned.
But as with hurricanes, there is some nuance to climate’s role in wildfires. Rising temperatures and less precipitation have had a bigger effect on fire risk in a temperate region like Northern California but has less of an impact in an area that’s already hot and dry, like Los Angeles County.
At the moment, scientists say they haven’t detected a climate signal in fire patterns in this region. But in study published in Environmental Research Letters in 2015, researchers projected that the area scorched by wildfires in Southern California will grow by as much as 77 percent by the middle of the century due to warming.
Worldwide, 2017 is shaping up to be the most expensive year for climate disasters ever. In the US, it’s already the most costly year ever for hurricanes and for wildfires.
Such expensive weather events are part of an ongoing trend. Since 1980, there have been 218 disasters across the United States with costs topping $1 billion.
