Hello Warsaw: Greenland ice loss will be OK 'even under extreme scenarios'
There really 'isn't any consensus' on sea levels
Opinion The UN Climate Change Conference in Warsaw is set to wind up tomorrow, probably without establishing any real prospect of human carbon emissions being seriously reduced in the foreseeable future. Many are worried that this could mean disastrous rises in sea level this century, with associated human misery on a grand scale.
In particular, concern often focuses on the Greenland ice sheet in this context. The Antarctic ice sheet, the other major landbased ice mass that might conceivably slide into the sea and melt, is so huge and thick that scientists believe it will resist the effects of any possible level of warming for thousands of years. And the mountain glaciers of central Asia, which the UN once erroneously foretold would all be gone by 2035, are actually looking good.
But Greenland, smaller and not so vast as Antarctica - yet vast enough that if all its water were to melt, massive sea level rises of seven metres could occur, as the hippies* at Greenpeace never tire of telling us - remains a worry for many. The actual ice sheet melting in place any time soon isn't a realistic concern - it is too massive - but it's possible that meltwater might get under the sheet, especially at the edges, and make it slip into the sea more rapidly than it generally does anyway as ice is forced off Greenland (by the weight of snow piling on top of the sheet and making more). Conceivably the rate of ice flow into the sea might accelerate rapidly, far ahead of the rate of replenishment by snow, causing a dangerous amount of sea level rise.
But there's reassurance even here. An article just published in the Proceedings of the National Academy of Sciences outlines the work of a team of researchers from Britain and Australia. These scientists investigated the effects on ice flow into the sea of meltwater increases, particularly the massive summer melt last year that caused so much concern.
In short, there's absolutely nothing to worry about:
Our findings suggest that annual motion of land-terminating margins of the ice sheet, and thus the projected dynamic contribution of these margins to sea level rise, is insensitive to melt volumes commensurate with temperature projections for 2100 ... despite record summer melting, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in 2009 ... surface melt–induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios. [Our emphasis]
And that's probably the most plausible mechanism for any seriously accelerated sea level rise this century blown, so to speak, out of the water. No wonder recent all-causes forecasts now suggest a rise of no more than 30cm even in the worst possible carbon-belching case - and more probably less, in other words no major change from the 20th century.
This is, of course, not the scenario the UN Intergovernmental Panel on Climate Change is working to - its latest report, just out, says that we could well get a metre of rise this century if we don't change our ways. More hardline activists, for instance the Climate Central campaign body funded by Google's Eric Schmidt, are still holding out for one-to-two metres.
That's probably why in the run-up to the IPCC report's being signed off, a group of eminent specialists tried to assure the drafters that no matter what anyone tells you about the state of climate science in general, there is no scientific consensus (their exact peer-reviewed words) on sea-level rise - which is probably the most compelling reason to actually do anything expensive about climate change.
A point to note: There is probably no country more menaced by sea-level rises than the Netherlands, as most of it is already below sea level. The Dutch plan to be ready for more-than-1m rises by 2100, and expect this to cost them just €1bn annually - a tiny sum compared to the costs of moving to renewable power. ®