First, historically privileged northern societies might not decline geopolitically, as many commentators have predicted. Indeed, the great age of northern power may lie ahead, if Earth’s very climate is on the verge of conferring boons to that part of the world. Should it turn out that headlong fossil-fuel combustion by northern nations has set in motion climate change that strengthens the relative world position of those same nations, future essayists will have a field day. But the prospect is serious. By the middle of the 21st century, a new global balance of power may emerge in which Russia and America are once again the world’s paired superpowers—only this time during a Warming War instead of a Cold War.

Second, if northern societies find that climate change makes them more wealthy, the quest for world equity could be dealt a huge setback. Despite the popular misconception, globalized economics have been a positive force for increased equity. As the Indian economist Surjit Bhalla has shown, the developing world produced 29 percent of the globe’s income in 1950; by 2000 that share had risen to 42 percent, while the developing world’s share of population rose at a slower rate. All other things being equal, we might expect continued economic globalization to distribute wealth more widely. But if climate change increases the value of northern land and resources, while leaving nations near the equator hotter and wracked by storms or droughts, all other things would not be equal.

That brings us to the third great concern: If climate change causes developing nations to falter, and social conditions within them deteriorate, many millions of jobless or hungry refugees may come to the borders of the favored North, demanding to be let in. If the very Earth itself turns against poor nations, punishing them with heat and storms, how could the United States morally deny the refugees succor?

Shifts in the relative values of places and resources have often led to war, and it is all too imaginable that climate change will cause nations to envy each other’s territory. This envy is likely to run both north-south and up-down. North-south? Suppose climate change made Brazil less habitable, while bringing an agreeable mild clime to the vast and fertile Argentinean pampas to Brazil’s south. São Paulo is already one of the world’s largest cities. Would a desperate, overheated Brazil of the year 2037—its population exploding—hesitate to attack Argentina for cool, inviting land? Now consider the up-down prospect: the desire to leave low-lying areas for altitude. Here’s an example: Since its independence, in 1947, Pakistan has kept a hand in the internal affairs of Afghanistan. Today Americans view this issue through the lens of the Taliban and al-Qaeda, but from Islamabad’s perspective, the goal has always been to keep Afghanistan available as a place for retreat, should Pakistan lose a war with India. What if the climate warms, rendering much of Pakistan unbearable to its citizens? (Temperatures of 100-plus degrees are already common in the Punjab.) Afghanistan’s high plateaus, dry and rocky as they are, might start looking pleasingly temperate as Pakistan warms, and the Afghans might see yet another army headed their way.

A warming climate could cause other landgrabs on a national scale. Today Greenland is a largely self-governing territory of Denmark that the world leaves in peace because no nation covets its shivering expanse. Should the Earth warm, Copenhagen might assert greater jurisdiction over Greenland, or stronger governments might scheme to seize this dwarf continent, which is roughly three times the size of Texas. Today Antarctica is under international administration, and this arrangement is generally accepted because the continent has no value beyond scientific research. If the world warmed for a long time—and it would likely take centuries for the Antarctic ice sheet to melt completely—international jockeying to seize or conquer Antarctica might become intense. Some geologists believe large oil deposits are under the Antarctic crust: In earlier epochs, the austral pole was densely vegetated and had conditions suitable for the formation of fossil fuels.