For the doomsayers of the 1950s, there was no doubt how America would end—the only question was how big the mushroom cloud would be. Climate change is the nuclear war of the 21st century. The Bulletin of the Atomic Scientists'Doomsday Clock, inaugurated in 1947, has long charted the waxing and waning of the nuclear threat; in 2007, the clock operators started working the climate menace into their calculations. And just as political scientist Herman Kahn was the bard of nuclear terror, scientists like James Hansen and James Lovelock lay out our coming environmental apocalypse in gory detail: the droughts and fires, the drowned cities, the massive die-offs. In his latest book, The Vanishing Face of Gaia, Lovelock writes that "global heating may all but eliminate people from Earth."
There's a danger in believing that our generation's existential crisis will be the one that destroys us. In a Weekly Standard piece on "The Icarus Syndrome," Jim Manzi notes the parallels between Britain's 1860s "Coal Panic" and the modern disaster scenarios of peak oil and climate doom. But the fact that coal shortages and the Cold War didn't vanquish the modern world doesn't prove that climate-change fears are overstated. It just means we survived long enough for something else to destroy us. So, let's assume we can't stop climate change with policy, changed behavior, or by dumping iron into the ocean. How could global warming bring about the end of America?
It's reasonable to argue that climate change alone couldn't possibly kill the United States. Earth won't become a superheated sphere all at once, and we should have the wherewithal to adjust to a warmer world. Manzi argues that, given the Intergovernmental Panel on Climate Change estimate of a 3-degree increase in global temperature by 2100, "the United States is expected to experience no net material economic costs [from anthropogenic global warming] … through the end of this century." At the other extreme is the specter of swift weather cataclysm. Peter Schwartz and Doug Randall, who wrote a brief on "abrupt climate change" for the Department of Defense, argue that climate chaos will be nonlinear—that "clear signs of environmental catastrophe will be evident in a few decades, not centuries."
Even if Manzi's calculus is correct—temperatures increase gradually and we learn to adapt—climate change could still melt America. It just won't happen in the next 90 years. Even in the best case, global warming has the potential to get worse over time, and to exacerbate a bunch of other potential America-killers. It is, in military parlance, a "threat multiplier": It will increase energy demands, intensify water shortages, and strain international relations. In a 2007 CNA Corporation report on climate change and national security, retired U.S. Navy Adm. T. Joseph Lopez predicts that global warming will bring on "[m]ore poverty, more forced migrations, higher unemployment. Those conditions are ripe for extremists and terrorists."
People around the world will, in short, be poorer, thirstier, and more desperate. This isn't just an educated guess—past societies have collapsed because of changes in temperature and precipitation. In The Great Warming: Climate Change and the Rise and Fall of Civilizations, Brian Fagan documents the demise of the Pueblo Indian civilization at Chaco Canyon (in what's now New Mexico) during the Medieval Warm Period (roughly between 800 and 1300 A.D.). Faced with massive droughts, individual families set out in search of more water and better land. Eventually, no one was left.
The Dust Bowl is modern America's closest analogue to Chaco Canyon. Okies began their migration slowly, with movement from the South and Great Plains to the West Coast picking up as droughts got worse and the national economy collapsed. Robert McLeman, a University of Ottawa geographer who studies climate migration, says the rich mostly stayed put, not wanting to abandon their land holdings. The poor couldn't afford to leave, instead packing into makeshift communities close to home—the Depression's version of refugee camps. The most mobile group: the working middle class, particularly those with Californian relatives.
Depression-era climate migrants didn't get a friendly reception. In 1936, the Los Angeles Police Department set up a "bum blockade," forcing new arrivals with "no visible means of support" to turn around and go home. While the police claimed 60 percent of the travelers had criminal records, later LAPD research revealed "the 'Okies' were mostly religious, hard-working agricultural laborers with families." The blockade ultimately ended after just two months, both because it was completely illegal and on account of bad PR—a movie director named John Langan sued the police department when he was mistakenly stopped at the border. (He was wearing dirty clothes.)
Even if America sells its soul to keep everyone else out, the country will have to contract. The Great Plains could turn into a Sahara-style wasteland. Cities like New Orleans and Miami—and maybe Boston and New York —could be abandoned once recurrent storms and rising sea levels render them too expensive to save. (Recent climate models suggest that America's East Coast might see sea levels rising higher and faster than any other population center in the world.) There's also an unfortunate overlap between America's fastest-growing regions and the most-likely focal points of climate Armageddon. Phoenix, Los Angeles, and the rest of the West will have to deal with drought, extreme heat, and water shortages; Florida and Houston will get attacked by superstorms. Even worse, the U.S. population is expected to double by 2100 —and those extra folks will continue packing into Arizona and California and Florida.