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Where will Americans live in the next 25 years?

By Chris Hayes 5-6 minutes

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One of the most interesting questions, perhaps the most interesting question, about where America will be in 25 years is where Americans, literally, will live. And that's inextricably linked to the most pressing unknown we collectively face, which is: Just how hot will our planet get?

The last decades in the U.S. have seen a steady internal migration, driven less by persecution or deprivation and more by weather.

One way to tell the story of this country is as a series of migrations. The first, of course, was the arrival on the continent of Europeans, who promptly forced a second mass migration and ethnic cleansing of the Indigenous people who had lived here for millennia. Soon thereafter, masses of slaves were imported to the American South as white Americans kept pushing the frontier west, forcing more and more Native people off their land until there was nowhere left for them to go.

In 1890, the U.S. Census director famously declared that the frontier was closed — but that didn't stop people from moving. Millions of European immigrants arrived at our shores fleeing starvation and persecution, millions of Black Southerners fled north desperately hoping to escape the tyranny of authoritarian apartheid post-Reconstruction, and Dust Bowl refugees fled west to the alleged land of bread and honey in California.

We don't think of our current age in the same terms, but the last decades in the U.S. have seen a steady internal migration, driven less by persecution or deprivation and more by weather. The states of the South, the Sun Belt and the Pacific Northwest have been gaining in population, while on the whole, the industrial Midwest and the Northeast have been losing population.

This unmistakable and consistent movement from places with freezing winters toward places with scorching summers is due to one of the single most important inventions in human history: the air conditioner.

AC has allowed Americans to move en masse to regions that previously would have been considered unpleasant or even uninhabitable. But as the effects of climate change send temperatures soaring, this shift is getting more complicated. This summer has already had multiple deadly heat waves, with more sure to come.

All of which brings us to the question about demographic geography for the next part of this century: How hot will it get in the hot parts of the country, and what will it mean for where people live?

Air conditioning, while basically a civilizational miracle, is also in a category of its own when it comes to electricity consumption.

Will people still be moving to Maricopa County, Arizona, if summer heat waves bring routine spikes to 120 degrees? Can Texas sustain its population growth if its temperatures routinely push its state-only electricity grid past the breaking point?

Keep in mind that air conditioning, while basically a civilizational miracle, is also in a category of its own when it comes to electricity consumption. There's a reason blackouts happen during the summer, and hotter temperatures will only cause more grid stress, which is likely to lead to more frequent outages.

Beyond the financial and the social consequences of millions upon millions of people blasting their air conditioners, hotter temperatures can mean the expansion of wildfire season. As fires expand across the West, their intensity will increase and air quality will suffer. Droughts will also get worse. Nearly the entire U.S. west of the Colorado River — cities like Phoenix, Denver, Albuquerque and Las Vegas — is basically a desert that shouldn't really be able to support dense human populations. The herculean efforts of the Army Corps of Engineers over decades to channel the sparse water available to the various population centers that need it have worked for the past few decades. But there's no guarantee they will work for the next quarter- century, let alone half.

Maybe, just maybe, we'll rapidly adapt our infrastructure in the hottest places in the country. Maybe the Sun Belt will lead the way in adopting geothermal energy and solar power and water efficiency (Las Vegas has already made some very impressive gains on the latter). Maybe the Sun Belt will, against the odds, continue to bloom. Or maybe we'll see mass disruption and population movement equivalent to the Northern Migration and the Dust Bowl exodus combined.

Either way, the political demographic dynamics are almost certainly about to shift dramatically. These shifts will affect and structure American life in ways we can only begin to imagine.

Chris Hayes

Chris Hayes hosts “All In with Chris Hayes” at 8 p.m. ET Monday through Friday on MSNBC. He is the editor-at-large at The Nation. A former fellow at Harvard University’s Edmond J. Safra Foundation Center for Ethics, Hayes was a Bernard Schwartz Fellow at the New America Foundation. His latest book is "A Colony in a Nation" (W. W. Norton).