Al Shaw, Abrahm Lustgarten, ProPublica, and Jeremy W. Goldsmith, Special to ProPublica • September 15, 2020
According to new data from the Rhodium Group analyzed by ProPublica and The New York Times Magazine, warming temperatures and changing rainfall will drive agriculture and temperate climates northward, while sea level rise will consume coastlines and dangerous levels of humidity will swamp the Mississippi River valley.
Taken with other recent research showing that the most habitable climate in North America will shift northward and the incidence of large fires will increase across the country, this suggests that the climate crisis will profoundly interrupt the way we live and farm in the United States. See how the North American places where humans have lived for thousands of years will shift and what changes are in store for your county.
In a paper published in the Proceedings of the National Academy of Sciences, a team of researchers modeled the human climate “niche”: the regions where temperature and precipitation have been most suitable for humans to live in over the past 6,000 years.
In the United States, that niche today blankets the heart of the country, from the Atlantic seaboard through northern Texas and Nebraska, and the California coast.
But as the climate warms, the niche could shift drastically northward. Under even a moderate carbon emissions scenario (known as RCP 4.5), by 2070 much of the Southeast becomes less suitable and the niche shifts toward the Midwest.
In the case of extreme warming (represented as RCP 8.5), the niche moves sharply toward Canada, leaving much of the lower half of the U.S. too hot or dry for the type of climate humans historically have lived in. Both scenarios suggest massive upheavals in where Americans currently live and grow food.
Heat is one of the largest drivers changing the niche of human habitability. Rhodium Group researchers estimate that under the RCP 8.5 scenario, between 2040 and 2060 extreme temperatures will become commonplace in the South and Southwest, with some counties in Arizona experiencing temperatures above 95 degrees for half the year.
Heat alone, however, won’t determine Americans’ fate. A new climate analysis — presented for the first time here — projects how humidity and heat will collide to form “wet bulb” temperatures that will disrupt the norms of daily existence.
Today, the combination of truly dangerous heat and humidity is rare. But by 2050, parts of the Midwest and Louisiana could see conditions that make it difficult for the human body to cool itself for nearly one out of every 20 days in the year. New projections for farm productivity also suggest that growing food will become difficult across large parts of the country, including the heart of the High Plains’ $35 billion agriculture industry. All the while, sea level rise will transform the coasts.
Combined, these factors will lead to profound economic losses — and possibly mass migration of Americans away from distress in much of the southern and coastal regions of the country. Meanwhile, the northern Midwest and Great Plains will benefit, in farm productivity, in economy and in overall comfort.
Extreme Heat and Humidity: 2040-2060
When heat meets excessive humidity, the body can no longer cool itself by sweating. That combination creates wet bulb temperatures, where 82 degrees can feel like southern Alabama on its hottest day, making it dangerous to work outdoors and for children to play school sports. As wet bulb temperatures increase even higher, so will the risk of heat stroke — and even death.
By midcentury, heat and humidity in Missouri A will feel like Louisiana does today, while some areas we don't usually think of as humid, like southwestern Arizona B, will see soaring wet bulb temperatures because of factors like sun angle, wind speed and cloud cover reacting to high temperatures, according to Hannah Hess of the Rhodium Group.
Large Wildfires: 2040-2071
With heat and evermore prevalent drought, the likelihood that very large wildfires (ones that burn over 12,000 acres) will affect U.S. regions increases substantially, particularly in the West, Northwest and the Rocky Mountains, but also in Florida, Georgia and the Southeast, according to peer-reviewed research published in the International Journal of Wildland Fire.
By midcentury, the northern Great Basin, though not a densely forested region, will become the epicenter of large wildfires A. These large, remote counties in Nevada and Oregon see cycles of wet and dry weather that turn the grassland into the fuel for fires that can easily rip through 10,000 acres a day with strong winds, said John Abatzoglou, one of the authors of the study.
Sea Level Rise: 2040-2060
As sea levels rise, the share of property submerged by high tides increases dramatically, affecting a small sliver of the nation's land but a disproportionate share of its population.
Some 50 million Americans live in eight of the largest U.S. metro areas — Miami A, New York B and Boston C among them — which all lie in some of the most affected counties in the U.S.
Farm Crop Yields: 2040-2060
With rising temperatures, it will become more difficult to grow food. Corn and soy are the most prevalent crops in the U.S. and the basis for livestock feed and other staple foods, and they have critical economic significance. Because of their broad regional spread, they offer the best proxy for predicting how farming will be affected by rising temperatures and changing water supplies.
Corn and soy production is more sensitive to heat than drought, and it will decrease for every degree of warming. By midcentury, North Dakota A, which already harvests millions of acres of both crops, will warm enough to allow for more growing days and higher yields. But parts of Texas and Oklahoma B may see yields drop by more than 70%.
Economic Damages From Climate: 2040-2060
Rising energy costs, lower labor productivity, poor crop yields and increasing crime are among the climate-driven elements that will increasingly drag on the U.S. economy, eventually taking a financial toll that exceeds that from the COVID-19 pandemic in some regions. Rhodium measured how much damage — or how much of a benefit — those counties might see, as a share of their GDP.
Populous cities with expensive real estate, including Houston A and Miami B, will see damage tallied in the billions — losses worth several percentage points of GDP — largely driven by storms, sea level rise and deaths from high heat, Hess said. Climate will have a larger proportional impact in rural places like Gulf County, Florida C, which might lose half its economy.
The Greatest Climate Risk? Compounding Calamities.
Taken together, some parts of the U.S. will see a number of issues stack on top of one another — heat and humidity may make it harder to work outside, while the ocean continues to claim more coastal land. The table below ranks the most at-risk counties in the U.S. if all of the perils were combined. You can also sort by individual climate risk to see how each one stacks up, with higher numbers being worse in all categories. The projections are for 2040-2060 under RCP 8.5.