Little of it is about “nature” per se, and none concerns the tragic fate of the planet’s animals, which has been written about so elegantly and poetically by others that, like our sea-level myopia, it threatens to occlude our picture of what global warming means for us, the human animal. Until now, it seems to have been easier for us to empathize with the climate plight of other species than our own, perhaps because we have such a hard time acknowledging or understanding our own responsibility and complicity in the changes now unfolding, and such an easier time evaluating the morally simpler calculus of pure victimhood.
What follows is instead a kaleidoscopic accounting of the human costs of human life continuing as it has for a generation, which will fill up the planet with only more humans—what ongoing global warming spells for public health, for conflict, for politics and food production and pop culture, for urban life and mental health and the way we imagine our own futures as we begin to perceive, all around us, an acceleration of history and the diminishing of possibility that acceleration likely brings. The force of retribution will cascade down to us through nature, but the cost to nature is only one part of the story; we will all be hurting. I may be in the minority in feeling that the world could lose much of what we think of as “nature,” as far as I cared, so long as we could go on living as we have in the world left behind. The problem is, we can’t.
II
Elements of Chaos
Heat Death
Humans, like all mammals, are heat engines; surviving means having to continually cool off, as panting dogs do. For that, the temperature needs to be low enough for the air to act as a kind of refrigerant, drawing heat off the skin so the engine can keep pumping. At seven degrees of warming, that would become impossible for portions of the planet’s equatorial band, and especially the tropics, where humidity adds to the problem. And the effect would be fast: after a few hours, a human body would be cooked to death from both inside and out.
At eleven or twelve degrees Celsius of warming, more than half the world’s population, as distributed today, would die of direct heat. Things almost certainly won’t get that hot anytime soon, though some models of unabated emissions do bring us that far eventually, over centuries. But at just five degrees, according to some calculations, whole parts of the globe would be literally unsurvivable for humans. At six, summer labor of any kind would become impossible in the lower Mississippi Valley, and everybody in the United States east of the Rockies would suffer more from heat than anyone, anywhere, in the world today. New York City would be hotter than present-day Bahrain, one of the planet’s hottest spots, and the temperature in Bahrain “would induce hyperthermia in even sleeping humans.”
Five or six degrees is unlikely by 2100. The IPCC furnishes us with a median prediction of over four degrees, should we continue down the current emissions path. That would deliver what today seems like unthinkable impacts—wildfires burning sixteen times as much land in the American West, hundreds of drowned cities. Cities now home to millions, across India and the Middle East, would become so hot that stepping outside in summer would be a lethal risk—in fact, they will become that way much sooner, with as little as two degrees of warming. You do not need to consider worst-case scenarios to become alarmed.
With direct heat, the key factor is something called “wet-bulb temperature,” which also measures humidity in a combined method as home-laboratory-kit as it sounds: the temperature is registered on a thermometer wrapped in a damp sock as it’s swung around in the air. At present, most regions reach a wet-bulb maximum of 26 or 27 degrees Celsius; the true red line for habitability is 35 degrees, beyond which humans begin simply dying from the heat. That leaves a gap of 8 degrees. What is called “heat stress” comes much sooner.
Actually, we’re there already. Since 1980, the planet has experienced a fiftyfold increase in the number of dangerous heat waves; a bigger increase is to come. The five warmest summers in Europe since 1500 have all occurred since 2002, and eventually, the IPCC warns, simply working outdoors at that time of year will be unhealthy for parts of the globe. Even if we meet the Paris goals, cities like Karachi and Kolkata will annually encounter deadly heat waves like those that crippled them in 2015, when heat killed thousands in India and Pakistan. At four degrees, the deadly European heat wave of 2003, which killed as many as 2,000 people a day, will be a normal summer. Then, it was one of the worst weather events in Continental history, killing 35,000 Europeans, including 14,000 French; perversely, the infirm fared relatively well, William Langewiesche has written, most of them watched over in the nursing homes and hospitals of those well-off countries, and it was the comparatively healthy elderly who accounted for most of the dead, many left behind by vacationing families escaping the heat, with some corpses rotting for weeks before the families returned.
It will get worse. In that “business as usual” scenario, a research team led by Ethan Coffel calculated in 2017, the number of days warmer than what were once the warmest days of the year could grow by a factor of 100 by 2080. Possibly by a factor of 250. The metric Coffel uses is “person-days”: a unit that combines the number of people affected with the number of days. Every year, there would be between 150 and 750 million person-days with wet-bulb temperatures equivalent to today’s most severe—i.e., quite deadly—heat waves. There would be a million person-days each year with intolerable wet-bulb temperatures—combinations of heat and humidity beyond the human capacity for survival. By the end of the century, the World Bank has estimated, the coolest months in tropical South America, Africa, and the Pacific are likely to be warmer than the warmest months at the end of the twentieth century.
We had heat waves back then, of course, deadly ones; in 1998, the Indian summer killed 2,500. More recently, temperature spikes have gotten hotter. In 2010, 55,000 died in a Russian heat wave that killed 700 people in Moscow each day. In 2016, in the midst of a heat wave that baked the Middle East for several months, temperatures in Iraq broke 100 degrees Fahrenheit in May, 110 in June, and 120 in July, with temperatures dipping below 100, most days, only at night. (A Shiite cleric in Najaf proclaimed the heat was the result of an electromagnetic attack on the country by American forces, according to The Wall Street Journal, and some state meteorologists agreed.) In 2018, the hottest temperature likely ever recorded in April was registered in southeast Pakistan. In India, a single day over 95 degrees Fahrenheit increases annual mortality rates by three-quarters of a percent; in 2016, a string of days topped 120—in May. In Saudi Arabia, where summer temperatures often approach that mark, 700,000 barrels of oil are burned each day in the summer, mostly to power the nation’s air-conditioning.
That can help with the heat, of course, but air conditioners and fans already account for fully 10 percent of global electricity consumption. Demand is expected to triple, or perhaps quadruple, by 2050; according to one estimate, the world will be adding 700 million AC units by just 2030. Another study suggests that by 2050 there will be, around the world, more than nine billion cooling appliances of various kinds. But, the climate-controlled malls of the Arab emirates aside, it is not remotely economical, let alone “green,” to wholesale air-condition all the hottest parts of the planet, many of them also the poorest. And indeed, the crisis will be most dramatic across the Middle East and Persian Gulf, where in 2015 the heat index registered temperatures as high as 163 degrees Fahrenheit. As soon as several decades from now, the hajj will become physically impossible for many of the two million Muslims who currently make the pilgrimage each year.