As it happens, Zika may also be a good model of a second worrying effect—disease mutation. One reason you hadn’t heard about Zika until recently is that it had been trapped in Uganda and Southeast Asia; another is that it did not, until recently, appear to cause birth defects. Scientists still don’t entirely understand what happened or what they missed, even now, several years after the planet seemed gripped by panic about microcephaly: it could be that the disease changed as it came to the Americas, the result of a genetic mutation or in adaptive response to a new environment; or that Zika produces those devastating prenatal effects only when another disease is present, possibly one less common in Africa; or that something about the environment or immunological history in Uganda protects mothers and their unborn children.
But there are things we do know for sure about how climate affects some diseases. Malaria, for instance, thrives in hotter regions, which is one reason the World Bank estimates that by 2030, 3.6 billion people will be reckoning with it—100 million as a direct result of climate change.
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Projections like those depend not just on climate models but on an intricate understanding of the organism at play. Or, rather, organisms. Malaria transmission involves both the disease and the mosquito; Lyme disease, both the disease and the tick—which is another epidemiologically threatening creature whose universe is rapidly expanding, thanks to global warming. As Mary Beth Pfeiffer has documented, Lyme case counts have spiked in Japan, Turkey, and South Korea, where the disease was literally nonexistent as recently as 2010—zero cases—and now lives inside hundreds more Koreans each year. In the Netherlands, 54 percent of the country’s land is now infested; in Europe as a whole, Lyme caseloads are now three times the standard level. In the United States, there are likely around 300,000 new infections each year—and since many of even those treated for Lyme continue to show symptoms years after treatment, the numbers can stockpile. Overall, the number of disease cases from mosquitoes, ticks, and fleas have tripled in the U.S. over just the last thirteen years, with dozens of counties across the country encountering ticks for the first time. But the effects of the epidemic can be seen perhaps most clearly in animals other than humans: in Minnesota, during the 2000s, winter ticks helped drop the moose population by 58 percent in a single decade, and some environmentalists believe the species could be eradicated entirely from the state as soon as 2020. In New England, dead moose calves have been found suckling as many as 90,000 engorged ticks, often killing the calves not through Lyme disease but simple anemia, the effect of that number of bugs each drawing a few milliliters of blood from the moose. Those that survive are far from robust, many having scratched so incessantly at their own hides to clear it of ticks that they completely eliminated their own hair, leaving behind a spooky gray skin that has earned them the name “ghost moose.”
Lyme is still, in relative terms, a young disease, and one we don’t yet understand all that well: we attribute a very mysterious and incoherent set of symptoms to it, from joint pain to fatigue to memory loss to facial palsy, almost as a catchall explanation for ailments we cannot pinpoint in patients who we know have been bitten by a bug carrying the bug. We do know ticks, however, as surely as we know malaria—there are not many parasites we understand better. But there are many, many millions we understand worse, which means our sense of how climate change will redirect or remodel them is shrouded in a foreboding ignorance. And then there are the plagues that climate change will confront us with for the very first time—a whole new universe of diseases humans have never before known to even worry about.
“New universe” is not hyperbole. Scientists guess the planet could harbor more than a million yet-to-be-discovered viruses. Bacteria are even trickier, and so we probably know about even fewer of them.
Perhaps scariest are those that live within us, peacefully for now. More than 99 percent of even those bacteria inside human bodies are presently unknown to science, which means we are operating in near-total ignorance about the effects climate change might have on the bugs in, for instance, our guts—about how many of the bacteria modern humans have come to rely on, like unseen factory workers, for everything from digesting our food to modulating our anxiety, could be rewired, diminished, or entirely killed off by an additional few degrees of heat.
Overwhelmingly, of course, the viruses and bacteria making homes inside us are nonthreatening to humans—at present. Presumably, a difference of a degree or two in global temperature won’t dramatically change the behavior of the majority of them—probably the vast majority, even the overwhelming majority. But consider the case of the saiga—the adorable, dwarflike antelope, native to central Asia. In May 2015, nearly two-thirds of the global population died in the span of just days—every single saiga in an area the size of Florida, the land suddenly dotted with hundreds of thousands of saiga carcasses and not one lone survivor. An event like this is called a “mega-death,” this one so striking and cinematic that it gave rise, immediately, to a whole raft of conspiracy theories: aliens, radiation, dumped rocket fuel. But no toxins were found by researchers poking through the killing fields—in the animals themselves, in the soil, in the local plants. The culprit, it turned out, was a simple bacteria, Pasteurella multocida, which had lived inside the saiga’s tonsils, without threatening its host in any way, for many, many generations. Suddenly it had proliferated, emigrated to the bloodstream, and from there to the animals’ liver, kidneys, and spleen. Why? “The places where the saigas died in May 2015 were extremely warm and humid,” Ed Yong wrote in The Atlantic. “In fact, humidity levels were the highest ever seen in the region since records began in 1948. The same pattern held for two earlier, and much smaller, die-offs from 1981 and 1988. When the temperature gets really hot, and the air gets really wet, saiga die. Climate is the trigger, Pasteurella is the bullet.”
This is not to say we now understand what precisely about humidity weaponized Pasteurella, or how many of the other bacteria living inside mammals like us—the 1 percent we have identified, or perhaps more worryingly the 99 percent we house without any knowledge or understanding—might be similarly triggered by climate, friendly, symbiotic bugs with whom we’ve lived in some cases for millions of years, transformed suddenly into contagions already inside us. That remains a mystery. But ignorance is no comfort. Presumably climate change will introduce us to some of them.
Economic Collapse
The murmuring mantra of global markets—which prevailed between the end of the Cold War and the onset of the Great Recession, promising something like their own eternal reign—is that economic growth will save us from anything and everything.
But in the aftermath of the 2008 crash, a number of historians and iconoclastic economists studying what they call “fossil capitalism” have started to suggest that the entire history of swift economic growth, which began somewhat suddenly in the eighteenth century, is not the result of innovation or the dynamics of free trade, but simply our discovery of fossil fuels and all their raw power—a onetime injection of that new “value” into a system that had previously been characterized by unending subsistence living. This is a minority view, among economists, and yet the précis version of the perspective is quite powerful. Before fossil fuels, nobody lived better than their parents or grandparents or ancestors from five hundred years before, except in the immediate aftermath of a great plague like the Black Death, which allowed the lucky survivors to gobble up the resources liberated by mass graves.
In the West especially, we tend to believe we’ve invented our way out of that endless zero-sum, scratch-and-claw resource scramble—both with particular innovations, like the steam engine and computer, and with the development of a dynamic capitalistic system to reward them. But scholars like Andreas Malm have a different perspective: we have been extracted from that muck only by a singular innovation, one engineered not by entrepreneurial human hands but in fact millions of years before the
first ones ever dug at the earth—engineered by time and geologic weight, which many millennia ago pressed the fossils of Earth’s earlier carbon-based life forms (plants, small animals) into petroleum, like lemon under a press. Oil is the patrimony of the planet’s prehuman past: what stored energy the earth can produce when undisturbed for millennia. As soon as humans discovered that storehouse, they set about plundering it—so fast that, at various points over the last half century, oil forecasters have panicked about running out. In 1968, the labor historian Eric Hobsbawm wrote, “Whoever says Industrial Revolution, says cotton.” Today, he would probably substitute “fossil fuel.”
The timeline of growth is just about perfectly consistent with the burning of those fuels, though doctrinaire economists would argue there is much more to the equation of growth. Generations being as long as they are and historical memory as short, the West’s several centuries of relatively reliable and expanding prosperity have endowed economic growth with the reassuring aura of permanence: we expect it, on some continents, at least, and rage against our leaders and elites when it does not come. But planetary history is very long, and human history, though a briefer interval, is long, too. And while the pace of technological change we call progress is today dizzying and may yet invent new ways of buffering us from the blows of climate change, it is also not hard to imagine those flush centuries, enjoyed by nations who colonized the rest of the planet to produce them, as an aberration. Earlier empires had boom years, too.
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You do not have to believe that economic growth is a mirage produced by fossil fumes to worry that climate change is a threat to it—in fact, this proposition forms the cornerstone around which an entire edifice of academic literature has been built over the last decade. The most exciting research on the economics of warming has come from Solomon Hsiang and Marshall Burke and Edward Miguel, who are not historians of fossil capitalism but who offer some very bleak analysis of their own: in a country that’s already relatively warm, every degree Celsius of warming reduces growth, on average, by about one percentage point (an enormous number, considering we count growth in the low single digits as “strong”). This is the sterling work in the field. Compared to the trajectory of economic growth with no climate change, their average projection is for a 23 percent loss in per capita earning globally by the end of this century.
Tracing the shape of the probability curve is even scarier. There is a 51 percent chance, this research suggests, that climate change will reduce global output by more than 20 percent by 2100, compared with a world without warming, and a 12 percent chance that it lowers per capita GDP by 50 percent or more by then, unless emissions decline. By comparison, the Great Depression dropped global GDP by about 15 percent, it is estimated—the numbers weren’t so good back then. The more recent Great Recession lowered it by about 2 percent, in a onetime shock; Hsiang and his colleagues estimate a one-in-eight chance of an ongoing and irreversible effect by 2100 that is twenty-five times worse. In 2018, a team led by Thomas Stoerk suggested that these estimates could be dramatic underestimates.
The scale of that economic devastation is hard to comprehend. Even within the postindustrial nations of the wealthy West, where economic indicators such as the unemployment rate and GDP growth circulate as though they contain the whole meaning of life in them, figures like these are a little bit hard to fathom; we’ve become so used to economic stability and reliable growth that the entire spectrum of conceivability stretches from contractions of about 15 percent, effects we study still in histories of the Depression, to growth about half as fast—about 7 percent, which the world as a whole last achieved during the global boom of the early 1960s. These are exceptional onetime peaks and troughs, extending for no more than a few years, and most of the time we measure economic fluctuations in ticks of decimal points—2.9 this year, 2.7 that. What climate change proposes is an economic setback of an entirely different category.
The breakdown by country is perhaps even more alarming. There are places that benefit, in the north, where warmer temperatures can improve agriculture and economic productivity: Canada, Russia, Scandinavia, Greenland. But in the mid-latitudes, the countries that produce the bulk of the world’s economic activity—the United States, China—lose nearly half of their potential output. The warming near the equator is worse, with losses throughout Africa, from Mexico to Brazil, and in India and Southeast Asia approaching 100 percent. India alone, one study proposed, would shoulder nearly a quarter of the economic suffering inflicted on the entire world by climate change. In 2018, the World Bank estimated that the current path of carbon emissions would sharply diminish the living conditions of 800 million living throughout South Asia. One hundred million, they say, will be dragged into extreme poverty by climate change just over the next decade. Perhaps “back into” is more appropriate: many of the most vulnerable are those populations that have just extracted themselves from deprivation and subsistence living, through developing-world growth powered by industrialization and fossil fuel.
And to help buffer or offset the impacts, we have no New Deal revival waiting around the corner, no Marshall Plan ready. The global halving of economic resources would be permanent, and, because permanent, we would soon not even know it as deprivation, only as a brutally cruel normal against which we might measure tiny burps of decimal-point growth as the breath of a new prosperity. We have gotten used to setbacks on our erratic march along the arc of economic history, but we know them as setbacks and expect elastic recoveries. What climate change has in store is not that kind of thing—not a Great Recession or a Great Depression but, in economic terms, a Great Dying.
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How could that come to be? The answer is partly in the preceding chapters—natural disaster, flooding, public health crises. All of these are not just tragedies but expensive ones, and beginning already to accumulate at an unprecedented rate. There is the cost to agriculture: more than three million Americans work on more than two million farms; if yields decline by 40 percent, margins will decline, too, in many cases disappearing entirely, the small farms and cooperatives and even empires of agribusinesses slipping underwater (to use the oddly apposite accountant’s metaphor) and drowning under debt all those who own and work those arid fields, many of them old enough to remember the same plains’ age of plenty. And then there is the real flooding: 2.4 million American homes and businesses, representing more than $1 trillion in present-day value, will suffer chronic flooding by 2100, according to a 2018 study by the Union of Concerned Scientists. Fourteen percent of the real estate in Miami Beach could be flooded by just 2045. This is just within America, though it isn’t only South Florida; in fact, over the next few decades, the real-estate impact will be almost $30 billion in New Jersey alone.
There is a direct heat cost to growth, as there is to health. Some of these effects we can see already—for instance, the warping of train tracks or the grounding of flights due to temperatures so high that they abolish the aerodynamics that allow planes to take off, which is now commonplace at heat-stricken airports like the one in Phoenix. (Every round-trip plane ticket from New York to London, keep in mind, costs the Arctic three more square meters of ice.) From Switzerland to Finland, heat waves have necessitated the closure of power plants when cooling liquids have become too hot to do their job. And in India, in 2012, 670 million lost power when the country’s grid was overwhelmed by farmers irrigating their fields without the help of the monsoon season, which never arrived. In all but the shiniest projects in all but the wealthiest parts of the world, the planet’s infrastructure was simply not built for climate change, which means the vulnerabilities are everywhere you look.
Other, less obvious effects are also visible—for instance, productivity. For the past few decades, economists have wondered why the computer revolution and the internet have not brought meaningful productivity gains to the industrialized world. Spreadsheets,
database management software, email—these innovations alone would seem to promise huge gains in efficiency for any business or economy adopting them. But those gains simply haven’t materialized; in fact, the economic period in which those innovations were introduced, along with literally thousands of similar computer-driven efficiencies, has been characterized, especially in the developed West, by wage and productivity stagnation and dampened economic growth. One speculative possibility: computers have made us more efficient and productive, but at the same time climate change has had the opposite effect, diminishing or wiping out entirely the impact of technology. How could this be? One theory is the negative cognitive effects of direct heat and air pollution, both of which are accumulating more research support by the day. And whether or not that theory explains the great stagnation of the last several decades, we do know that, globally, warmer temperatures do dampen worker productivity.
The claim seems both far-fetched and intuitive, since, on the one hand, you don’t imagine a few ticks of temperature would turn entire economies into zombie markets, and since, on the other, you yourself have surely labored at work on a hot day with the air-conditioning out and understand how hard that can be. The bigger-picture perspective is harder to swallow, at least at first. It may sound like geographic determinism, but Hsiang, Burke, and Miguel have identified an optimal annual average temperature for economic productivity: 13 degrees Celsius, which just so happens to be the historical median for the United States and several other of the world’s biggest economies. Today, the U.S. climate hovers around 13.4 degrees, which translates into less than 1 percent of GDP loss—though, like compound interest, the effects grow over time. Of course, as the country has warmed over the last decades, particular regions have seen their temperatures rise, some of them from suboptimal levels to something closer to an ideal setting, climate-wise. The greater San Francisco Bay Area, for instance, is sitting pretty right now, at exactly 13 degrees.
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