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In February 2020, I traveled to New York to celebrate a zeroth birthday and an 80th birthday. First, I saw a close friend’s baby, who had been born only a month earlier. The next day, I went to my grandmother’s birthday party at a crowded Italian restaurant near Times Square.
I would say that this experience made me think about aging and what the alleged Soviet spy Alger Hiss (of all people) called “the Great Span”: the way that seemingly distant history is only a few lifetimes away. But this would be a writer’s white lie. I think about time’s bucket brigade probably too much, and I am constantly looking for tidy anecdotes. Weeks earlier, I had already written in the notes app of my phone: “When my friend’s baby is my grandmother’s age, it will be 2100.”
And 2100 is an important year in climate science.
Last week, two major papers on sea-level rise were published. Both try to answer the greatest outstanding questions about sea-level rise: How much will the oceans rise, and how fast? Their conclusions are either reassuring or frightening, depending on your optimism about how quickly the world will get a handle on its carbon pollution.
The first paper, written by 84 scientists, shares the results from a portfolio of the newest climate models and is clearly meant to shape the Intergovernmental Panel on Climate Change’s sixth assessment report. If countries follow the path they have currently committed to under the Paris Agreement, the world’s average temperature will rise about 3 degrees Celsius by 2100. That will induce about 25 centimeters, or about 10 inches, of sea-level rise, according to the median model run, the new paper finds. But if countries manage to hold warming to 1.5 degrees Celsius, as they now aspire to do, then the median sea-level rise falls to about half that amount.
But the second paper has a more worrying message. Led by the glaciologists Rob DeConto and David Pollard, it looks specifically at how Antarctica will melt. For the past few years, DeConto and Pollard have investigated a hypothetical phenomenon called marine ice-cliff instability that could vastly accelerate Antarctica’s demise. Several of the largest glaciers in West Antarctica form massive ice cliffs that rise hundreds or thousands of feet above the ocean’s surface. DeConto and Pollard have worried that, as the ocean warms, these ice cliffs could destabilize, entering a runaway feedback loop that disintegrates the entire glacier in a matter of decades. It would be bad. (Other researchers doubt that this rapid decay is even possible: It was the hottest debate in glaciology in the 2010s.)
Happily, DeConto and his colleagues found that rapid ice-cliff collapse is unlikely to happen if we keep global temperature rise below 1.5 or even 2 degrees Celsius. But if countries continue on their current path of 3 degrees Celsius, then ice cliffs could very well decay and abruptly bump the pace of sea-level rise after 2060. Sea levels would rise about an inch every five years by 2100 entirely because of Antarctica; ice melt from Greenland, mountain glaciers, and the expansion of warmer ocean water would contribute too. That pace is at least 10 times what Antarctica is contributing today.
I’ll have more to say on these studies soon. But first I’d note that the first paper goes up to only 2100. That year has been the end date for climate projections since the Intergovernmental Panel on Climate Change’s first summary report, in 1990. Yet when sea-level-rise scientists share further projections of their work at academic panels, and in the DeConto and Pollard paper, many of the results are scarier for the 22nd century. Some runaway feedback loops that have not kicked in by 2100 will kick in by 2150.
“Who cares?” you might think. “That’s a long way away, and surely we’ll have technology to modify the climate by then.” But that gets to the second and more interesting finding of DeConto and Pollard’s paper. They also model the effect of direct carbon removal: What would happen if we stayed on the current high-pollution pathway until 2040, 2050, or 2060, and then—in a moment of pique—began to aggressively remove carbon from the atmosphere?
And here the runaway nature of marine ice-cliff instability really kicks in. If you start rapid carbon removal anytime after 2070, they find, West Antarctica’s largest glaciers have already slipped into a feedback loop of doom. The problem becomes unfixable. If you begin carbon removal by 2060, on the other hand, then you can preserve much more of the ice sheet.
Ten years, in other words, makes a world of difference. That tight timeline is one reason that I think it’s important to spend public funds on direct carbon-removal technology today. I read once that it takes about as long to develop a new technology as it does to raise a child. We need to start the clock on carbon removal now so it will be ready when we need it.
It’s worth remembering how quickly American progressives’ positions on the timing of climate policy have shifted; a few years ago, the leftmost senators endorsed the 100 by ’50 Act. This bill aimed to phase out fossil fuels on the power grid by 2050; President Joe Biden’s target for the same goal is now 15 years earlier. (He shares the bill’s larger goal of reaching a net-zero economy by 2050.)
The U.S. target has moved forward for many reasons, among them that the public now better understands the dangers of overshooting 1.5 degrees Celsius. But these closer targets, I have come to think, are not just better for the planet’s long-term geologic stability. They are easier to think with too; they bring climate change within our mental horizons. I entered the full-time labor force in 2013, and the software that runs my 401(k) account assumes that I will retire sometime between 2055 and 2065. By then, under the Biden plan, the U.S. should be ironing out the final kinks in its decarbonization, and developing countries should be near to joining it. I say should; nothing is certain—a technological leap, a political upheaval, or, God forbid, world war could derail the timing. But aiming to settle climate change within the U.S. by 2050 is clarifying nonetheless. It puts decarbonization on the same timeline as questions about how to spend a life—where to work and live, whether to start a family, and the rest.
The 2050 timeline means that decarbonizing will be the work of a lifetime: my lifetime. You could say our lifetime, if you were born between 1980 and 2005. We will see the task through. For people much older, the journey will end with miles left to travel; for younger people, decarbonizing will—or, at least, should—be something like a solved problem. A child born today won’t enter the professional workforce until 2043; under the current timeline, decarbonization will be just about licked by the time they turn 30. Their job will be to live with climate change: They will see Antarctica’s crucial 2050s in the prime of their career. Today’s babies are the scientists, engineers, and policy staff who will deal with marine ice-cliff instability.
James Hansen turned 80 earlier this year. In 1988, when he presented his climate models to the Senate, he was 47. The year 2100 was a long time away—far outside any plausible policy-making range. But 2100’s Social Security beneficiaries are today’s toddlers. Their children will see the 22nd century.