A shutdown of the conveyor belt is not a scenario that any credible scientists worry about on any human timescale. But a slowdown is another matter. Already, climate change has depressed the velocity of the Gulf Stream by as much as 15 percent, a development that scientists call “an unprecedented event in the past millennium,” believed to be one reason the sea-level rise along the East Coast of the United States is dramatically higher than elsewhere in the world. And in 2018, two major papers triggered a new wave of concern over the conveyor belt, technically called Atlantic Meridional Overturning Circulation, which was found to be moving at its slowest rate in at least 1,500 years. This had happened about a hundred years ahead of the schedule of even alarmed scientists and marked what the climate scientist Michael Mann called, ominously, a “tipping point.” Further change, of course, is to come: the transformation of the ocean by warming making these unknown waters doubly unknowable, remodeling the planet’s seas before we ever were able to discover their depths and all the life submerged there.
Unbreathable Air
Our lungs need oxygen, but it is only a fraction of what we breathe, and the fraction tends to decline the more carbon is in the atmosphere. That doesn’t mean we are at risk of suffocation—oxygen is far too abundant for that—but we will nevertheless suffer. With CO2 at 930 parts per million (more than double where we are today), cognitive ability declines by 21 percent.
The effects are more pronounced indoors, where CO2 tends to build up—that’s one reason you probably feel a little more awake when taking a brisk walk outside than you do after spending a long day inside with the windows closed. And it’s also a reason elementary school classrooms have been found, by one study, to already average 1,000 parts per million, with almost a quarter of those surveyed in Texas over 3,000—quite alarming numbers, given that these are the environments we’ve designed to promote intellectual performance. But classrooms are not the worst offenders: other studies have shown even higher concentrations on airplanes, with effects you can probably groggily recall from past experience.
But carbon is, more or less, the least of it. Going forward, the planet’s air won’t just be warmer; it will likely also be dirtier, more oppressive, and more sickening. Droughts have a direct impact on air quality, producing what is now known as dust exposure and in the days of the American Dust Bowl was called “dust pneumonia”; climate change will bring new dust storms to those plains states, where deaths from dust pollution are expected to more than double and hospitalizations to triple. The hotter the planet gets, the more ozone forms, and by the middle of this century Americans should suffer a 70 percent increase in days with unhealthy ozone smog, the National Center for Atmospheric Research has projected. By the 2090s, as many as 2 billion people globally will be breathing air above the WHO “safe” level. Already, more than 10,000 people die from air pollution daily. That is considerably more each day—each day—than the total number of people who have ever been affected by the meltdowns of nuclear reactors. This is not a slam-dunk argument in favor of nuclear power, of course, since the comparison isn’t so neat: there are many, many more fossil fuel chimneys disgorging their trails of black smoke than fission facilities with their finger-trap towers and clouds of white vapor. But it is a startling mark of just how all-encompassing our regime of carbon pollution really is, enclosing the planet in a toxic swaddle.
In recent years, researchers have uncovered a whole secret history of adversity woven into the experience of the last half century by the hand of leaded gasoline and lead paint, which seem to have dramatically increased rates of intellectual disability and criminality, and dramatically decreased educational attainment and lifetime earnings, wherever they were introduced. The effects of air pollution seem starker already. Small-particulate pollution, for instance, lowers cognitive performance over time so much that researchers call the effect “huge”: reducing Chinese pollution to the EPA standard, for instance, would improve the country’s verbal test scores by 13 percent and its math scores by 8 percent. (Simple temperature rise has a robust and negative impact on test taking, too: scores go down when it’s hotter out.) Pollution has been linked with increased mental illness in children and the likelihood of dementia in adults. A higher pollution level in the year a baby is born has been shown to reduce earnings and labor force participation at age thirty, and the relationship of pollution to premature births and low birth weight of babies is so strong that the simple introduction of E-ZPass in American cities reduced both problems, in the vicinity of toll plazas, by 10.8 percent and 11.8 percent, respectively, just by cutting down on the exhaust expelled when cars slowed to pay the toll.
Then there is the more familiar health threat from pollution. In 2013, melting Arctic ice remodeled Asian weather patterns, depriving industrial China of the natural wind-ventilation patterns it had come to depend on, and, as a result, blanketing much of the country’s north in an unbreathable smog. An obtuse-seeming metric called the Air Quality Index categorizes the risks according to an idiosyncratic unit scale tabulating the presence of a variety of pollutants: the warnings begin at 51–100, and at 201–300 include promises of “significant increase in respiratory effects in the general population.” The index tops out with the 301–500 range, warning of “serious aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly” and “serious risk of respiratory effects in the general population”; at that level, “everyone should avoid all outdoor exertion.” The Chinese “airpocalypse” of 2013 doubled the high end of that upper range, reaching a peak Air Quality Index of 993, and scientists studying the phenomenon suggested that China had inadvertently invented an entirely new and unstudied kind of smog, one that combined the “pea soup” pollution of industrial-era Europe and the small-particulate pollution that has lately contaminated so much of the developing world. That year, smog was responsible for 1.37 million deaths in the country.
Outside of China, most saw the photographs and video of a world capital blanketed by gray so thick it blotted out the sun as a sign, not of the state of the planet’s atmosphere, but of just how backward that one country was—just how far China lagged behind the quality-of-life indices of the first world, whatever its rapid economic growth suggested about its place in the global pecking order. Then, in the record California wildfire season of 2017, the air around San Francisco was worse than on the same day in Beijing. In Napa, the Air Quality Index hit 486. In Los Angeles, there was a run on surgical masks; in Santa Barbara, residents scooped ash from their drainpipes by the handful. In Seattle, the following year, wildfire smoke made it unsafe for anyone, anywhere, to breathe outside. Which gave Americans one more reason—panic about their own health—to look away from the situation in Delhi, where in 2017 the Air Quality Index reached 999.
The Indian capital is home to 26 million people. In 2017, simply breathing its air was the equivalent of smoking more than two packs of cigarettes a day, and local hospitals saw a patient surge of 20 percent. Runners in Delhi’s half marathon competed with their heads wrapped by white masks. And air that thick with smut is hazardous in other ways: visibility was so low that cars crashed in pileups on Delhi’s highways, and United canceled flights in and out of the city.