Bryan Walsh

Aug 16 · 7 min read

Asteroids, supervolcanoes, nuclear war, climate change, engineered viruses, artificial intelligence, and even aliens — the end may be closer than you think. For the next two weeks, OneZero will be featuring essays drawn from editor Bryan Walsh’s forthcoming book End Times: A Brief Guide to the End of the World, which hits shelves on August 27 and is available for pre-order now, as well as pieces by other experts in the burgeoning field of existential risk. But we’re not helpless. It’s up to us to postpone the apocalypse.

That the natural world is degraded from what it once was is indisputable. If Christopher Columbus were to arrive in the Americas today aboard his Niña, Pinta, and Santa Maria, he would find 30% less biodiversity than in 1492. The global population of vertebrates has declined by 52% between 1970 and 2010. The current extinction rate is 100 to 1,000 times higher than it has been during normal — meaning non-mass extinction — periods in biological history, with amphibians going extinct 45,000 times faster than the norm. One point eight trillion pieces of plastic trash, weighing 79,000 tons, now occupies an area three times the size of France in the Pacific Ocean — and this Great Pacific Garbage Patch is expected to grow 22% by 2025. And of course, there is the climate change that has happened — about 1.6 F in warming since 1901 — and the climate change that is to come.

Yet amid all this natural loss, human beings, on the aggregate, have largely thrived. That’s definitely true compared to the days of Columbus — the economist Angus Maddison estimates that between 1500 and 2008, global average per capita gross domestic product (GDP) multiplied by more than thirteenfold. Much of that gain has occurred in recent years, as globalization helped lift more than a billion people out of extreme poverty in the developing world since 1990 alone — the same years when environmental damage, including the first signs of climate change, began compounding.

Nor is this simply a story of GDP. The Human Development Index (HDI) is a composite statistic developed by the Pakistani economist Mahbub ul Haq to track life expectancy and education, as well as per capita income. Graph every country for HDI since 1990 and you’ll see — with the occasional ups and downs of individual nations — a decidedly rising trend that shows no signs of reversing.

Amid all this natural loss, human beings, on the aggregate, have largely thrived. That’s definitely true compared to the days of Columbus — the economist Angus Maddison estimates that between 1500 and 2008, global average per capita gross domestic product (GDP) multiplied by more than thirteenfold.

Perhaps a better way to understand that picture is to look at those years when economic growth temporarily halted, and rolled backward: the 2008 global financial crisis and its immediate aftermath. The Great Recession led to a loss of more than $2 trillion in economic growth globally, a reduction of nearly 4%. By one estimate the crisis cost every American nearly $70,000 in lifetime income.

But that’s just money. The real human cost of the financial crisis was in broken families, sickness, even death. One study found that the crisis was associated with at least 260,000 excess cancer-related deaths around the world, many of them treatable. As unemployment rates rose, so did suicide rates — a correlation that has been seen in past financial crises. The destabilizing wave of populism around the world can be traced back to the 2008 crisis, and how its aftermath was mismanaged.

Nothing we’ve experienced with climate change or any other environmental threat compares — yet — to the sheer suffering that was inflicted on the world when the wheels of growth temporarily stopped. “We’re still dealing with the political and economic blowback from the 2008 financial crisis, and everything about it makes climate change seem like a walk in the park,” said Ted Nordhaus, the executive director of the Breakthrough Institute, an environmental research center in Oakland.

This picture — a degrading natural world poised against a generally improving humanity — has a name: the environmentalist’s paradox. In 2010, a team of researchers led by Ciara Raudsepp-Hearne at McGill University tried to figure out what could explain it. They came up with four hypotheses. It could be that humanity only appears to be better off — but the numbers belie the conclusion that improved human well-being is an illusion, including those, like the HDI, that measure more than just economic growth. It may be that the remarkable improvements in food production over the past century are so important that they simply outweigh any environmental drawbacks, however severe. For most of human history, deadly famine was just one bad harvest away. That’s no longer the case for most of the world.

It may be that technological advances and increased wealth could make us less dependent on a healthy ecosystem, allowing the economy to continue to grow even amid environmental degradation. That third hypothesis — a brand of techno-optimism — is implicit in climate economics. In this view, at worst climate change will make us poorer than we might have been in its absence — but we’ll keep getting richer, much richer, than we are today.

If that really is how climate change will unfold, then it is not an existential risk. The natural world will continue to suffer, and we’ll be affected — some of us far more than others, including those who have done the least to contribute to the problem — but humanity, on the whole, will be okay. More than okay, at least by our generally grim historical standards.

But there’s a fourth possible answer to the environmentalist’s paradox: the worst is yet to come. In this hypothesis, the material benefits that humanity has enjoyed over the last few decades have been purchased on overextended carbon credit, and just as previous credit bubbles have inevitably led to painful economic contractions, so it will be with our subprime environmental loans. The desire of 7 billion-plus human beings for an American-style middle-class lifestyle, with all the energy and meat and pollution that entails, is not sustainable, environmentally or economically. The bill will come due, and when it does, no degree of innovation will save us from collapse.

Climate change in this scenario very much is an existential risk. Not only are there environmental limits that we can’t innovate our way around, but there are tipping points waiting for us as the climate warms — and we exceed them at existential peril.

The uncertainty at the core of the environmentalist’s paradox is emblematic of global warming science more generally. Why provide only one answer when you can have four — or more? Climate scientists try to predict the future by constructing models that anticipate both how humans will react to warming — by reducing carbon emissions or substituting energy sources — and how the climate itself will respond to those efforts. Those models spit out an array of different scenarios for the future — more than a thousand in the IPCC’s most recent assessment — that are further whittled down into projections that feature a range of possible future climates.

Skeptics often seize on the uncertainty as evidence that climate change isn’t real or isn’t something we need to worry about. They’re dead wrong — the physical basis behind the science of man-made climate change are well established, and existing climate models have been confirmed by real-world warming over the past several decades. But in part to avoid giving skeptics more ammunition, scientists tend to emphasize the most likely, middle-of-the-road projections for future warming, rather than the extremes.

In its 2014 assessment of climate science, the IPCC reported that without significant emissions reductions, we’re most likely to experience warming in the range of 7 F above preindustrial levels by the end of the century. Seven degrees Fahrenheit would be almost twice the 3.6 F rise that the UN climate system was ostensibly formed to prevent, all the way back in 1992. It would be a climate warmer than anything Homo sapiens has ever experienced before, warmer than it was during the Pliocene epoch more than 3 million years ago, when sea levels were as much as 82 feet higher than they are today. Would that represent an existential threat? Perhaps — although some of the worst impacts, like the coastline-reshaping rise in sea level, would still take centuries more to play out, giving us time to adapt, perhaps in ways we can’t begin to anticipate now.

That’s the shock of climate change — the shock of a very nasty surprise, one that might just be enough to snuff out human life as we know it.

“Will the planet still be around then, too?” the climate economist Gernot Wagner asked when I visited his then-office in Cambridge, Massachusetts in 2018. “Yes. Will society as we know it? No. The rich will be fine. They’ll buy a second air conditioner and fly their private jet to Aspen. The poor as usual will suffer extraordinarily more than the rich. But is it an existential risk for them? No.”

The uncertainty in climate science runs both ways, however. The most likely outcome by the end of the century may be around 5.4 F of additional warming — or less if we either get much better at reducing carbon emissions or the climate system turns to be less sensitive to that carbon than we generally expect. But there’s about a 10% chance, as Wagner and Martin Weitzman describe in their 2015 book Climate Shock, that the uncertainty in those projections could skew in the other direction, and warming might be far worse: as much as 10.8 F by 2100 or more, with a 3% chance of 18 F warming.

That’s the shock that could be waiting in climate change — the shock of a very nasty surprise, one that might just be enough to snuff out human life as we know it.