In 2015, almost 200 nations signed an agreement in Paris aimed at limiting the increase in the global average temperature to 1.5 degrees Celsius above preindustrial levels. What happens when we pass that limit? The fact is, nobody knows. As scientists pointed out more than 60 years ago, modern society has undertaken an unprecedented global experiment by rapidly moving vast amounts of carbon into the seas and skies.
It’s an experiment in radical uncertainty and extreme risk. Carbon dioxide spikes similar to the one we’re causing are associated with most of the major extinction events in the earth’s history. There is substantial historical evidence that climate variation has had major impacts on human society, including contributing to political destabilization and societal collapse.
Even so, you might find comfort in the fact that climate change has happened in the past. Indeed, scientists look to paleoclimate history to understand what’s coming down the pike. But there are two major differences between the human-induced climate change happening now and past climate change. The first is that never before has so much carbon been moved from the ground so quickly. According to the National Oceanic and Atmospheric Administration, the “increase in atmospheric carbon dioxide over the past 60 years is 100-200 times faster than the increase that occurred at the end of the last ice age.’’
The speed and intensity of the climate experiment we’re running means that its effects are likely going to be more violent than those of past climate change. Previous climatic transitions that humans dealt with, like the end of the last ice age, were so slow they gave people time to migrate and adapt. But even those slow transitions had major effects. The climate change we face today is happening much faster than anything we’ve faced before, and the effects are likely to be much more traumatic.
The other way climate change differs today is that never before have there been more than 8 billion people living on the planet, nearly all of them connected in a technologically advanced global civilization dependent on cheap energy from fossil fuels. Most of the climate change humans have dealt with happened before there were cities and when human populations were small, mobile, and not dependent on complex infrastructure for basic survival. It’s one thing if you have to follow migrating elk because it’s getting a little warmer. It’s another if nearly every aspect of your life, from food to housing and medical care, depends on a sophisticated network of transportation and energy production built for a stable climate system now undergoing violent transformation.
Climate models suggest a range of outcomes depending on how much carbon we emit. These models are based on observed data, reconstruction of past change, and scientific understanding of the global climate system. Unfortunately, critical aspects of climate science remain poorly understood and contentious. We don’t really understand cloud dynamics, for instance, which are important for predicting how quickly things might warm. Nor is there clear agreement on topics like tipping points, glacier collapse, and the effects of methane release from Arctic permafrost.
Nevertheless, climate science offers general outlines of what’s to come, mostly ever more chaotic weather, including both extreme precipitation and increased drought, increased flooding, and sea level rise. Even now, on the cusp of 1.5 degrees Celsius warming, we see climate chaos causing trouble. As warming accelerates, that chaos will only get worse.
What climate models can’t do is predict how humans will react. There’s an old adage from statistician George Box: “All models are wrong, but some are useful.’’ Box’s point is that models are inherently biased and reductive: A map is not the territory. But a map can still help you get somewhere, if it’s a good map.
Unfortunately, the models from the Intergovernmental Panel on Climate Change and other big science organizations are not very good maps. They’re not only wrong in the sense Box means but dangerously biased and reductive in misleading ways. They often include presuppositions about the human response to climate change that are based on nothing more than wishful thinking — for instance, that countries will actually meet their climate commitments or that we’ll develop and implement cost-effective carbon removal at scale in time to prevent a rapid shift to a hotter planetary equilibrium.
If there’s one thing you learn from studying history, it’s that human beings are wildly unpredictable. We don’t know how social change happens, and we have zero data from the future. In political and cultural terms, our future is not only unknown but unknowable.
Some people find hope in that. An optimistic view of the past two centuries argues that things have been getting better and are likely to keep doing so, and that human beings’ innovative unpredictability gives us resilience in the face of adversity. Optimists point to new solar and wind farms and electric cars and legal rulings from the International Criminal Court as evidence that we’re hitting a “social tipping point.’’
Optimists also conveniently ignore that global energy consumption continues to rise, planetary warming is accelerating, and there’s no international governing body capable of forcing the largest greenhouse gas emitters like China and the United States to comply with any emissions regulations at all. A less optimistic view of the past two centuries — a time of technological development, increasing consumption, and unprecedented human impact — sees a bubble fueled by the voracious consumption of ancient carbon stocks, a bubble all but certain to burst.
One way to respond to our situation is with optimistic faith in progress; another is grounded in an empirical understanding of history and earth system science. It’s true that optimism is generally associated with better health and increased longevity. And humans seem to have an innate bias to look on the bright side, even to the point of self-delusion. But under conditions of high stakes, low information, and unpredictable outcomes, optimism isn’t just self-deluding, it’s reckless and irresponsible.
We don’t know what happens when we pass 1.5 degrees Celsius, but we’re going to find out. There’s considerable scientific confidence that increased warming is going to have significant impacts on human society. And there’s no good evidence for the optimistic claim that we’re going to see miraculous political and technological changes capable of stopping global warming or even coping with the consequences. We face a future at once radically unpredictable and deeply menacing.
What we need from our leaders and from one another is not optimism but an ethical pessimism grounded in the recognition of human limits. We’ve failed to stop climate change, and we’re failing to adapt to the climate chaos we’ve unleashed: Catastrophic drought is causing starvation, disrupting trade, and sparking fires around the world; increasingly devastating storms are displacing people from Alaska and California to Sri Lanka and Jamaica; climate change is driving an insurance crisis; more than 80 percent of the world’s coral reefs are bleaching because of heat stress; billions of people across the globe are increasingly subjected to heat stress from extreme heat; and while mass deportations might make good political theater, they don’t address the deeper problem of global climate-change-driven migration. And all this is only the beginning. There’s not going to be any solution: It’s going to be one disaster after another, followed by triage and salvage. But as I argue in my book “Impasse: Climate Change and the Limits of Progress,’’ pessimism offers a responsible and ethical framework for apprehending our situation.
What happens when we pass 1.5 degrees warming — or 2, 3, and 4 degrees? Nobody knows. The world we live in will pass away like so many fallen empires, and a new world will be born in its place. We might have been able to stop this once, but now it’s too late. With pessimism as our guide, maybe we can navigate the change with a little more compassion and wisdom. It might just be our only hope.