The Greenland ice sheet is melting faster than the “old” climate models had predicted, warns a report based on newer models. At the other end of the world, so is the Antarctic ice sheet but its enhanced melting will be countered by increased snowfall, according to the more recent models.
Greenland has already contributed around 25 percent of global sea level rise observed in recent decades, according to the report this month in the American Geophysical Union’s journal Geophysical Research Letters, which brought together over 60 researchers from 44 institutions.
According the latest climate models – on which the recent Intergovernmental Panel on Climate Change Sixth Assessment Report was based – Greenland will be contributing more to sea level rise than has been expected by 2100 (an arbitrarily chosen point). The Antarctic will be contributing about the same as the last round of climate models suggested.
The Greenland ice sheet is expected to take hundreds of years to disappear, because it’s over a mile thick at some points. If it does melt completely, and we’re heading in that trajectory, that island alone is expected to add 7 meters to global mean sea levels. Note that since the industrial revolution began around 150 years ago, tha mean sea level has risen by about 21 to 24 centimeters, most of that in the last couple of decades.
Starkly demonstrating these changes, as surface temperatures in Greenland have risen above freezing, rain fell on the highest point of its ice sheet for three days a week ago, instead of snow, for the first time in recorded history. This was no drizzle. The rain fell for hours at the ice sheet’s 3,216-meter summit starting Saturday, August 14 and ending on the Monday. Altogether 7 billion tons of rain poured onto the ice sheet during that period, Reuters reported. It’s hard to envision what exactly that means, but it’s bad news.
The melting affected 337,000 square miles of ice, NBC reported. “Water on ice is bad. It makes the ice sheet more prone to surface melt,” explains Indrani Das, a glaciologist with Columbia University’s Lamont-Doherty Earth Observatory.
Climate models formulated to date have been predicting dire consequences of climate change, but they are fundamental tools, not precision surgical instruments.
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The models can predict that Europe will grow hotter and that storms will intensify in terms of violence and will also stick around longer, but they’re not designed to foresee the sheer intensity of rain in Europe, Asia, the Indian subcontinent, the United States, and Africa. Some places reported a year’s worth of rain in a day, for instance. Climate models just don’t have local or short-scale resolution: At best they have monthly or seasonal resolution.
Improvement of climate models is by nature a never-ending quest. A key conundrum is the practically infinite data on the practically infinite number of interrelated parameters, which are interrelated; also, there are problems identifying crucial parameters from noise. Climate models can predict that certain aspects will have tipping points, but cannot identify let alone forecast tipping points or abrupt climate changes with precision.
Meanwhile, climate change is having different effects on different places: for instance, if the global mean increase in temperature since the industrial revolution began so far is about 1.2 degrees Celsius, it’s more like 2 degrees Celsius in the Arctic (a phenomenon known as “Arctic amplification” of global warming). Now it turns out that the ice sheets of the Antarctic and of Greenland are responding differently to global warming, according to the new models. And as the Lamont-Doherty labs have shown in other work, abrupt climate changes have happened before.
Now the new paper in the American Geophysical Union’s journal says the Antarctic, like Greenland, may melt faster than expected because the polar atmosphere will be warmer, but the Antarctic can also expect more snow accumulation. Hence, the upshot is that the extra contribution from the warming Antarctic may be countered at least in part by snowfall.
How much melt is expected from the Antarctic? A lot: nearly 60 meters if it all melts.
Even in a scenario of 1.5-degree Celsius average increase, Antarctica alone was expected to contribute about half a meter of sea level rise by 2100 (at the extreme tail-end of scenarios).
The bottom line is that the new models generally predict a greater contribution from the Greenland ice sheet by 2100 (again, an arbitrary point) but little change in projected sea level rise from Antarctica, explains Tony Payne, head of the University of Bristol’s School of Geographical Sciences and lead author of the new paper.
The last time humankind experienced significant global sea level rise was at the start of the Holocene, the modern era. Throughout the entire rise of civilization, we have known a stable sea level. John Englander, an oceanographer and researcher of the subject, suggests that the general failure to contend with the problem looming over the horizon is a failure of the imagination. In his recent newsletter on sea level rise, he dubs the Intergovernmental Panel’s sixth report “disaster by degrees” and he stresses that for all the noise about renewable energy and targets, our trajectory, in fact, remains worst-case scenario: “the warming continues – and is actually accelerating,” Englander writes.
“The recent findings suggest that society should plan for higher sea levels,” the Geophysical Union sums up in its article. Indeed. Archaeologists have found the odd hints at prehistoric attempts to fight sea level rise, which proved futile – such as a seawall that failed to protect a Neolithic village on Israel’s coast. Now the wall and village are underwater – and note again that the comparisons to 2100 mean nothing. Temperatures and sea levels are expected to continue rising far beyond that.