Jeff Goodell, The Doomsday Glacier
In the farthest reaches of Antarctica, a nightmare scenario of crumbling ice – and rapidly rising seas – could spell disaster for a warming planet.
This is terrifying.
A few years ago, James Hansen, the godfather of global-warming science, told me that he believed the IPCC estimates were far too conservative and that the waters could rise as much as 10 feet by 2100. For Hansen, the past is prologue. Three million years ago, during the Pliocene Epoch, when the level of CO2 in the atmosphere was about the same as it is today, and temperatures were only slightly warmer, the seas were at least 20 feet higher. That suggests there is a lot of melting to come before the ice sheets reach a happy equilibrium. Mountain glaciers could contribute a little bit, as would the thermal expansion of the oceans as they warmed, but to get to more than 20 feet of sea-level rise, Greenland and Antarctica would both have to contribute in a big way.
But in recent years, things have gotten weird in Antarctica. The first alarming event was the sudden collapse, in 2002, of the Larsen B ice shelf, a vast chunk of ice on the Antarctic Peninsula. An ice shelf is like an enormous fingernail that grows off the end of a glacier where it meets the water. The glaciers behind the Larsen B, like many glaciers in both Antarctica and Greenland, are known as “marine-terminating glaciers,” because large portions of them lie below sea level. The collapse of ice shelves does not in itself contribute to sea-level rise, since they are already floating (just like ice melting in a glass doesn’t raise the level of liquid). But they perform an important role in buttressing, or restraining, the glaciers. After the Larsen B ice shelf vanished, the glaciers that had been behind it started flowing into the sea up to eight times faster than they had before. “It was like, ‘Oh, what is going on here?' ” says Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. “It turns out glaciers are much more responsive than anyone thought.”
One day, Alley was thinking about a problem that Dave Pollard, a colleague at Penn State, and Rob DeConto, a climate scientist at the University of Massachusetts, Amherst, had been having with their climate model. DeConto and Pollard had been collaborating for years to develop a sophisticated model to help them understand the impact of warming from fossil-fuel pollution on Greenland and Antarctica. Climate models are computer programs that try to capture fundamental physics of the natural world, such as, if the temperature warms one degree, how much will the seas around the world rise? It is not a simple question, and requires calculating everything from changes in how much sunlight the ice reflects to how much one degree of heat causes the Atlantic Ocean to expand. Models have gotten a lot better in the past few decades, but they still can’t simulate all the processes in the real world.
One way that scientists test how well a model might predict the future is by seeing how well it recreates the past. If you can run a model backward and it gets things right, then you can run it forward and trust that the results might be accurate. For years, DeConto and Pollard have been trying to get their model to re-create the Pliocene, the era 3 million years ago when the CO2 levels in the atmosphere were very close to what they are today, except the seas were 20 feet higher. But no matter what knobs they turned, they couldn’t get their model to melt the ice sheets fast enough to replicate what the geological record told them had happened. “We knew something was missing from the dynamics of our model,” DeConto tells me.
Alley suggested they plug in his new understanding of ice physics, including the structural integrity of the ice itself (or lack thereof), and “see what happens.” They did, and lo, their model worked. They were able to get the Pliocene melt just about right. In effect, they found the missing mechanism. Their model was now road-tested for accuracy.
The next thing that DeConto and Pollard did, of course, was run the model forward. What they found was that, in high-emissions scenarios – that is, the track we are on today – instead of virtually zero contribution to sea-level rise from Antarctica by 2100, they got more than three feet, most of it from West Antarctica. If you add in a fairly conservative estimate of the contribution to sea-level rise from Greenland in the same time frame, as well as expansion of the oceans, you get more than six feet – that’s double the high-end IPCC scenario.
For anyone living in Miami Beach or Brooklyn or Boston’s Back Bay or any other low-lying coastal neighborhood, the difference between three feet of sea-level rise by 2100 and six feet is the difference between a wet but livable city and a submerged city – billions of dollars worth of coastal real estate, not to mention the lives of the 145 million people who live less than three feet above sea level, many of them in poor nations like Bangladesh and Indonesia. The difference between three feet and six feet is the difference between a manageable coastal evacuation and a decades-long refugee disaster. For many Pacific island nations, it is the difference between survival and extinction.
In any case, the threat is clear. In a rational world, awareness of these risks would lead to deep and rapid cuts in carbon pollution to slow the warming, as well as investment in more research in West Antarctica to get a clearer understanding of what is going on. Instead, Americans elected a president who thinks climate change is a hoax, who is hellbent on burning more fossil fuels, who installs the CEO of the world’s largest oil company as secretary of state, who wants to slash climate-science funding and instead spend nearly $70 billion to build a wall at the Mexican border and another $54 billion to beef up the military.
In the end, no one can say exactly how much longer the West Antarctica glaciers will remain stable. “We just don’t know what the upper boundary is for how fast this can happen,” Alley says, sounding a bit spooked. “We are dealing with an event that no human has ever witnessed before. We have no analogue for this.” But it is clear that thanks to our 200-year-long fossil-fuel binge, the collapse of West Antarctica is already underway, and every Miami Beach condo owner and Bangladeshi farmer is living at the mercy of ice physics right now. Alley himself would never put it this way, but in West Antarctica, scientists have discovered the engine of catastrophe.