"Extreme weather due to climate change displaced million people from their homes last year. It could soon reshape the nation.

"Hurricane Harvey, which hit Texas and Louisiana last August, causing $125 billion in damage, dumped more water out of the sky than any storm in U.S. history. By one calculation, roughly a million gallons fell for every person in Texas. The water rained down on a flat former bayou that had become a concrete and asphalt empire of more than 2.3 million people. Highways turned into rivers and shopping malls into lakes. As the water rose, people scrambled for safe refuge – into attics, onto rooftops and overpasses. A Texas game warden captured a nine-foot-long alligator in the dining room of a home near Lake Houston. Snakes swam into kitchens. A hawk flew into a taxicab and wouldn't leave.

"In 2017, a string of climate disasters  – six big hurricanes in the Atlantic, wildfires in the West, horrific mudslides, high-temperature records breaking all over the country – caused $306 billion in damage, killing more than 300 people. After Hurricane Maria, 300,000 Puerto Ricans fled to Florida, and disaster experts estimate that climate and weather events displaced more than 1 million Americans from their homes last year. These statistics don't begin to capture the emotional and financial toll on survivors who have to dig through ashes and flooded debris to rebuild their lives. Mental-health workers often see spikes in depression, PTSD and suicides in the months that follow a natural disaster. After Harvey, one study found that 30 percent of residents in flooded areas had fallen behind on their rent or mortgage. One in four respondents said they were having problems paying for food.

"In the not-so-distant future, places like Phoenix and Tucson will become so hot that just walking across the street will be a life-threatening event. Parts of the upper Middle West will become a permanent dust bowl. South Florida and low-lying sections of the Gulf Coast will be underwater. Some people may try to stick around and fight it out with Mother Nature, but most will not. People will do what they have done for thousands of years, says Vivek Shandas, a professor of urban studies and planning at Portland State University. They will migrate to better climates"

"In the U.S., a recent study by Mathew Hauer, a demographer at the University of Georgia, estimates that 13 million people will be displaced by sea-level rise alone by the year 2100 (about the number of African-Americans who moved out of the South during the Great Migration of the 20th century). In Hauer's study, about 2.5 million will flee the region that includes Miami, Fort Lauderdale and West Palm Beach. Greater New Orleans loses up to 500,000 people; the New York City area loses 50,000. The biggest winners are nearby cities on high ground with mild climates, good infrastructure and strong economies: Atlanta; Austin; Madison, Wisconsin; and Memphis.

"The Southeast will be the biggest loser due to damage from increased flooding, higher heat mortality and lower agricultural yield – in some of the poorest counties in the region, the study predicts, income will fall by up to one-third. In contrast, the Northwest will see increased agricultural yields, lower energy costs (due to milder winters) and higher worker productivity. The lesson of this study is, the future looks good for the Pacific Northwest, especially cities west of the Cascades, like Seattle and Portland, says Hsiang's co-author Amir Jina, an economist at the University of Chicago. For the Southeast, it's not a very pretty picture.

"At about 5 p.m. on August 29th, 2005, Hurricane Katrina broke through the levee protecting New Orleans' Lower Ninth Ward. Ten feet of raging seawater tore into this working-class black neighborhood, trapping people in their homes without warning. About 80 people were killed by the storm in the Lower Ninth, the highest flood fatality rate in the city. Virtually every structure in the 25-square-block neighborhood was destroyed.

"The Lower Ninth was ground zero, but Katrina devastated a wide area in and around New Orleans. About 1,800 people died; another 400,000 were displaced. This wave of displaced people became known as the Katrina diaspora, and researchers are still trying to come to grips with exactly what impact it had on the demographics of the city. By most measures, New Orleans is thriving again, but it is a richer, whiter city than it had been before the storm. It is also smaller: The population of New Orleans today is about 390,000, roughly 100,000 fewer people than before Katrina hit.

"The decision to move to safer climates is obviously deeply personal, influenced by a person's connection with the community they live in, their financial situation and their tolerance for risk. But for city officials in at-risk cities, homeowners are terrified. Once people start thinking about the long-term value of their homes and how they will be impacted by climate change, that changes the game completely, a county attorney in Florida says. What happens to the value of a house in, for instance, Fort Lauderdale, when the cost of flood insurance triples? When I think about the future of South Florida, it's flood insurance that scares me the most, Wayne Pathman, a prominent Miami lawyer and board member of Miami Beach's chamber of commerce, tells me.

"Some cities and counties already feel the financial noose tightening. In Monroe County, Florida, which includes the entire Florida Keys, a recent study estimated 150 miles of roads need to be raised in the coming years to prevent flooding. Road-raising costs in Monroe County run as much as $7 million a mile, potentially putting the overall price tag up to $1 billion. In 2018, the budget for all road work and repair in the county was only $25 million.

"Rather than struggle to adapt, it's often easier just to leave. Richard Hornbeck, a professor of economics at the University of Chicago who has studied the Dust Bowl extensively, argues that farmers in the 1930s could have adapted to changing conditions by planting different crops or shifting their fields to pastures for cattle or sheep. But they didn't. There was inertia in staying with how things had always been done, and too much investment in certain kinds of farm machinery, for people to make the changes needed, says Hornbeck. Instead of adapting, many just headed to California.

"They started thinking about other places to live, and settled on Asheville, North Carolina. Set at the edge of the Blue Ridge Mountains, Asheville (population 89,000) is an old railroad town known for good hiking, craft beer, a lively music scene and a mild climate. When we were looking for a place to move to, the choice was obvious, Kaplan says. Lots of other people apparently feel that way too. Buncombe County, where Asheville is located, is one of the fastest-growing counties in the East – between 2010 and 2016, the population grew about 7.4 percent, compared with 1 percent nationwide. Construction is going crazy, says Tom Barr, an Asheville businessman who helps rebuild urban infrastructure around the country. Realtors complain that they have no houses to sell.

"There are also hints about the global migrations that will result and are already happening due to climate change. One recent study in the journal Nature Climate Change predicts that by 2050, as much as 30 percent of the world's land surface could face desert like conditions, including large swaths of Asia, Europe, Africa and southern Australia. More than 1.5 billion people currently live in these regions."