But what would it take to entirely melt Antarctica, a sheet of miles-thick ice that's larger than the United States?
Now, a blockbuster new study has produced an answer: If we burned all the fossil fuel on Earth, we would, in fact, eliminate the Antarctic ice sheet. The process would likely take up to 10,000 years, but its consequences would cause nearly 200 feet of sea-level rise and irrevocably change the face of the Earth.
The Antarctica question -- whether there's actually enough fossil fuel in the world to raise global temperatures enough to melt the entire ice sheet -- surfaced at least as far back as 1979, when The New York Times published an article about the possible consequences of an Antarctic ice sheet collapse. This was the article that got climate scientist Ken Caldeira, a researcher at Stanford University's Carnegie Institute of Science and the new study's senior author, interested in climate change in the first place, and in the Antarctica question in particular.
"The problem has been in my head for 35 or so years, but I had never worked with people who had the tools to solve the problem," Caldeira says. "It was a real pleasure to finally get to address this question."
Caldeira teamed up with a group of other researchers including lead author Ricarda Winkelmann, a professor of climate system analysis at the Potsdam Institute for Climate Impact Research, to tackle the issue. The group used a state-of-the-art ice sheet model, which Winkelmann helped develop, to make projections on what would happen if humans burned various amounts of fossil fuels in the coming centuries, including what would happen if we burned all the available fuel on Earth - an amount equivalent to about 10,000 gigatons (that's 10,000 billion tons, or 10 trillion tons) of carbon, according to previous estimates.
While "more comprehensive" models do exist, the ice and climate models used in this study are well-known, well-tested and "have been applied successfully in many ways," said Richard Alley, a glaciologist at Pennsylvania State University, in an e-mail. The results they produced point to the possibility of a nearly unrecognizable future Earth.
It would probably only take us about 500 years to burn through all the fossil fuels, the researchers suggest. But carbon can stay in the atmosphere and cause global temperatures to remain elevated for thousands of years. So even though ice melts slowly, it's likely to continue melting for millennia.
When it comes to destroying Antarctic ice, the biggest culprit in all this melting is the warming of the ocean, even more-so than the warming of the air, Winkelmann explains. Warming waters can melt ice sheets from the bottom up, which can destabilize them and cause large ice shelves to start breaking off into the water. In the doomsday scenario described in the paper, the entire Antarctic Ice Sheet would eventually collapse.
The result would be nearly 60 meters, or close to 200 feet, of sea-level rise, about half of which would likely occur in the first 1,000 years. "This kind of sea-level rise would be unprecedented in the history of civilization," Winkelmann says, adding that these effects would be irreversible on human time scales. Such an enormous rate of sea-level rise would likely wipe out many of the world's coastal cities. In the United States, alone, San Francisco would be reduced to a handful of islands, New York City would be submerged and Florida would disappear entirely.
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