Heat waves that make Chicago feel like Las Vegas. Warming ocean temperatures that displace Maine’s lobsters. A year-round spike in disease-carrying mosquitoes in Florida.
These are just some of the ways climate change could play out across the country over the coming decades, according to the federal government’s National Climate Assessment, released over Thanksgiving weekend.
The last time the United States issued a version of this report, in 2014, critics said it would be stronger if it focused more on the impact of climate change on the local level. The new version of the report does just that — giving scores of accounts of how human-caused climate change is damaging the U.S. today and how it’s projected to wreak more havoc in cities, states and regions by the end of the century.
Assembled by scientists and administrators from 13 federal agencies, here are six of the most dramatic findings from the fourth National Climate Assessment:
MIDWEST HEAT WAVES
If the world continues pumping out Earth-warming greenhouse gases at current levels, Chicago could see almost as many 100-degree days by the year 2100 as Las Vegas experienced, on average, from 1981 to 2010, the study predicts.
Chicago hit 100 degrees Fahrenheit less than once a year on average between 1976 and 2005, the baseline period the study used for comparison. With no reduction in emissions of carbon dioxide and other greenhouse gases, the projected number of those very hot days would jump anywhere from 3 to 63 days per year by 2100, the study says. Las Vegas averaged 67 days with temperatures above 100 in the three decades ending in 2010, according to Jim Angel, state climatologist of Illinois, who helped draft the report.
The report acknowledges that there is a broad range of potential outcomes and that the degree of uncertainty about temperatures “becomes larger further into the future.” But it predicts a distinct warming trend across the Midwest.
(The report also said that Chicago could even approach Phoenix in the number of 100-degree days in the future. But one scientist involved in writing the Midwest chapter acknowledged to NBC News this week that the assertion had been in error. Phoenix recorded 110 days of 100 degrees or more, on the average, during the years between 1981 to 2010, far more than even the worst-case prediction for Chicago.)
A severe heat wave and drought that gripped the Midwest in 2012 has made the public more receptive to the idea that climate change is fueling severe weather, Angel said.
“There has been a lot more conversation than ever before on that topic,” Angel said. “And I think this new report will bring it to an even higher level.”
Outsized rain downpours have destabilized coastal bluffs, triggering landslides and regularly shutting down parts of Amtrak’s busy Portland-to-Seattle train service.
Extreme weather in the Pacific Northwest has included severe drought, large wildfires, heat waves and record blooms of harmful algae. But the regular disruptions along the busy Cascades rail corridor have gotten particular attention from commuters. A total of 240 breaks in service between 2009 and 2013 because of landslides amounted to more than a quarter of all landslide shutdowns for the past century.
The Pacific Northwest is no stranger to rain, but the impacts of global warming have made precipitation in the region less predictable — with unusual dry periods followed by deluges, and attendant landslides, the report’s authors say. Climate change is expected to continue raising the risk of landslides in the future, the study says.
“These are commuter lines that people use between Seattle or Bellingham [Washington] and Portland. It’s been hugely disruptive,” said Kris May, an environmental consultant and lead author of the report’s chapter on the Northwest.
Wildfires in the West have burned twice as much acreage since 1985 as they would have without climate change. And the area burned in the Sierra Nevada mountains could triple in the last three decades of this century, if humanity does nothing to check greenhouse gases, the report says.
The impact of severely dried brush and timber has been revealed in devastating terms in California in the last two years. The 2017 Thomas Fire burned more acres in Ventura and Santa Barbara counties than any fire in state history. And the recent Camp Fire killed more people, at least 88, and burned more residences, nearly 14,000, than any other California wildfire.