The Weekend Wonk: What This Week’s Antarctic Study Means
April 2, 2016
Is it possible that the most recent study of ice instability in Antarctica is cracking the unstable cliff face of climate denial? (how’s that for a tortured metaphor?)
Not enough information.
Above, National Snow and Ice Data Center lead scientist Ted Scambos sketches out the details. Below, I’ve posted Jason Box’s description of how many of the same processes anticipated for Antarctica are already at work in Greenland.
A new climate change study “jolts sea-rise predictions,” according to The Washington Post, with sea levels projected to increase so much that The New York Times says they would “likely provoke a profound crisis within the lifetimes of children being born today.” This disturbing news made the top-foldfront pages of the Post and the Times, but it was completely ignored by the broadcast television networks’ nightly news programs.
The nightly newscasts’ failure to cover this study follows a paltry year of climate change coverage on the broadcast networks in 2015. A Media Matters study found that ABC, CBS, and NBC collectively devoted less time to covering climate change during their nightly news and Sunday show broadcasts than they did in the previous year, even though 2015 was a landmark year for climate-related news that included the EPA finalizing the Clean Power Plan, Pope Francis issuing a climate change encyclical, President Obama rejecting the Keystone XL pipeline, and 195 countries around the world reaching a historic climate agreement in Paris.
The latest information comes via a breakthrough in simulating the behavior of Antarctica’s vast and complex network of glaciers and ice shelves. That’s brought a more complete understanding of how warmer air temperatures—projected to surpass those regularly experienced on Earth at any point during at least the last few million years—are affecting the sea level. At the same time, the study provides new certainty that—should the world act immediately to curb carbon emissions at a scale far beyond current efforts—virtually all Antarctic ice melt could be avoided.
We should take this result very seriously. The new study prompted a lapse into Ciceronian prose from the New York Times and an instant revision to sea level rise projection maps for coastal cities worldwide, with many observers noting that, at current effort levels, humanity is veering dangerously close to the worst-case scenario.
“Under the high emissions scenario, the 22nd century would be the century of hell,” Ben Strauss, a sea level scientist at Climate Central told the Washington Post. “There would really be an unthinkable level of sea rise. It would erase many major cities and some nations from the map.”
But well before then, in the lifetimes of people being born today, the new study points to a potentially existential threat for cities like Miami; Guangzhou, China; Mumbai, India; New Orleans; Boston; and Alexandria, Egypt. In a scenario in which global carbon emissions remain essentially unchecked, the study argues the world’s coastal cities could see an additional two feet of sea level by 2100 above previous estimates—about five feet total.
In an interview with Slate, lead author Rob DeConto said that his results would be “really, really bad news for the business-as-usual future.”
“That is literally remapping how the planet looks from space,” says study co-author Rob DeConto, a geoscientist at the University of Massachusetts Amherst. The good news, he says, is that it projects little or no sea-level rise from Antarctic melt if greenhouse-gas emissions are reduced quickly enough to limit the average global temperature rise to about 2 °C.
The findings add to a growing body of research that suggests that Antarctic ice is less stable than once thought. In its 2013 report2, the Intergovernmental Panel on Climate Change estimated that Antarctic melting would contribute just a few centimetres to sea-level rise by 2100. But as scientists develop a better understanding of how the ocean and atmosphere affect the ice sheet, their projections of the continent’s future are growing more dire.
DeConto and co-author David Pollard, a palaeoclimatologist at Pennsylvania State University in University Park, developed a climate model that accounts for ice loss caused by warming ocean currents — which can eat at the underside of the ice sheet — and for rising atmospheric temperatures that melt it from above. Ponds of meltwater that form on the ice surface often drain through cracks; this can set off a chain reaction that breaks up ice shelves and causes newly exposed ice cliffs to collapse under their own weight.
They found that by including all of these processes, they could better simulate key geological periods that have long puzzled scientists. Before the last ice age began 130,000–115,000 years ago, for instance, sea levels were 6–9 metres higher than today — yet atmospheric carbon-dioxide levels were about 30% lower. And 3 million years ago, when CO2 levels roughly equalled today’s, the oceans may have been 10–30 metres higher.