Article originally published on climatecodered.blogspot.com on 24 jan 10.
New research suggest that just two collapsing West Antarctic glaciers could add another half a metre to sea levels this century
The Victorian and Queensland governments decisions to stick to an "upper boundary" sea-level rise estimate of 0.8 metres by 2100 (and NSW at 0.9 metre) for planning purposes needs urgent revision, with new modelling showing two West Antarctic glaciers are past their tipping points.
The 0.8 metre estimate for sea-level rises to 2100 is already obsolete:
- The Copenhagen climate science congress of March 2009 estimated a sea-level rise of 0.75–1.9 metres by 2100
- The federal Department of Climate Change's November 2009 climate update reports estimates of a 0.5–2 metre rise by 2100
- A study published in the Proceedings of the National Academy of Sciences in December found that global average sea levels are likely to rise by between 75cm and190cm by the end of the century.
So how far could we reasonably expect sea levels to rise by 2100? As the world's oceans warm, they expand and sea-levels rise, but how quickly the loss of polar ice sheets will add to the rise is difficult to estimate, principally because ice-sheet and sea-ice dynamics are not sufficiently well understood, and they are subject to non-linear (rapid and unexpected) changes, such as is occurring with sea-ice in the Arctic. The question is no longer whether the Greenland and West Antarctic ice sheets are losing mass (they are!) but if and when they pass tipping points for large, irreversible ice mass loss, and how fast that will occur.
averaged over the five decades from 1957 to 2006 (both inclusive). For further
information on earthobservatory.nasa.gov web site, click on image.
Recent research by Blancon et. al published in Nature in 2009 examining the paleoclimate record shows sea level rises of 3 metres in 50 years due to the rapid melting of ice sheets 120,000 years ago. Mike Kearney, of the University of Maryland, said it's "within the realm of possibility" that global warming will trigger a sudden collapse of the West Antarctic ice sheet, which could lead to a rapid increase in sea levels like that predicted by the study.
Given the catastrophic failure to date of global climate policy-making (Copenhagen outcome =4-degree rise by 2100), big sea level rises are on the way for the sort of temperature increases now on the table. NASA climate science chief James Hansen wrote in New Scientist that:
Oxygen isotopes in the deep-ocean fossil plankton known as foraminifera reveal that the Earth was last 2°C to 3°C warmer around 3 million years ago, with carbon dioxide levels of perhaps 350 to 450 parts per million. It was a dramatically different planet then, with no Arctic sea-ice in the warm seasons and sea level about 25 meters higher, give or take 10 meters.
Even more compelling, Professor Eelco Rohling of University of Southampton says:
Even if we would curb all CO2 emissions today, and stabilise at the modern level (387 parts per million by volume), then our natural relationship suggests that sea level would continue to rise to about 25 metres above the present.
Then on 13 January this year, New Scientist published this story showing calculations that the Pine Island glacier in the West Antarctic has likely passed its tipping point, with researchers estimating that this one glacier alone could add a quarter of a metre to sea levels by 2100:
Major Antarctic glacier is 'past its tipping point'
A major Antarctic glacier has passed its tipping point, according to a new modelling study. After losing increasing amounts of ice over the past decades, it is poised to collapse in a catastrophe that could raise global sea levels by 24 centimetres.
Pine Island glacier (PIG) is one of many at the fringes of the West Antarctic ice sheet. In 2004, satellite observations showed that it had started to thin, and that ice was flowing into the Amundsen Sea 25 per cent faster than it had 30 years before.
Now, the first study to model changes in an ice sheet in three dimensions shows that PIG has probably passed a critical "tipping point" and is irreversibly on track to lose 50 per cent of its ice in as little as 100 years, significantly raising global sea levels.The team that carried out the study admits their model can represent only a simplified version of the physics that govern changes in glaciers, but say that if anything, the model is optimistic and PIG will disappear faster than it projects.
Richard Katz of the University of Oxford and colleagues developed the model to explore whether the retreat of the "grounding line" – the undersea junction at which a floating ice shelf becomes an ice sheet grounded on the sea bed – could cause ice sheets to collapse.
...
The model suggests that within 100 years, PIG's grounding line could have retreated over 200 kilometres. "Before the retreating grounding line comes to a rest at some unknown point on the inner slope, PIG will have lost 50 per cent of its ice, contributing 24 centimetres to global sea levels," says Richard Hindmarsh of the British Antarctic Survey, who did not participate in the study.
This assumes that the grounding line does eventually stabilise, after much of PIG is gone. In reality, PIG could disappear entirely, says Hindmarsh. "If Thwaite's glacier, which sits alongside PIG, also retreats, PIG's grounding line could retreat even further back to a second crest, causing sea levels to rise by 52 centimetres." The model suggests Thwaite's glacier has also passed its tipping point.
... and now comes a new report in Science that an undersea ridge that may have once helped slow the loss of the Pine Island glacier is no longer doing so ...
Antarctic Glacier Off Its Leash
An unmanned autonomous submarine has discovered a sea-floor ridge that may have been the last hope for stopping the now-accelerating retreat of the Pine Island Glacier, a crumbling keystone of the West Antarctic Ice Sheet, researchers announced at the fall meeting of the American Geophysical Union.
An unmanned autonomous submarine has discovered a sea-floor ridge that may have been the last hope for stopping the now-accelerating retreat of the Pine Island Glacier, a crumbling keystone of the West Antarctic Ice Sheet. The ridge appears to have once protected the glacier, but no more. The submarine found the glacier floating well off the ridge and warmer, ice-melting water passing over the ridge and farther under the ice. And no survey, underwater or airborne, has found another such glacier-preserving obstacle for the next 250 kilometers landward.
The Pine Island and adjacent Thwaites glaciers are key to the fate of West Antarctic ice, says glaciologist Richard Alley of Pennsylvania State University, University Park, in an e-mail. And West Antarctica is key to how fast and far sea level will rise in a warming world. "To a policymaker, I suspect that the continuing list of [such] ice-sheet surprises is not reassuring," he writes.
At the meeting, glaciologist Adrian Jenkins of the British Antarctic Survey in Cambridge and colleagues described how the instrument-laden Autosub3 cruised for 94 hours along 510 kilometers of track beneath the floating portion of the Pine Island Glacier in January 2009. The sub found a 300-meter-high ridge across the ocean cavity formed by the floating end of the glacier. Deep, warmer water was overtopping the ridge and passing through the gap between floating ice and the ridge top on its way to melting back more of the glacier. That gap has been growing, Jenkins said, perhaps since the 1970s. An aerial photograph from 1973 shows a bump in the ice where the ridge is now known to be, suggesting that the ice was then resting on the ridge and no warmer water could have been getting through.
Although the last physical obstacle to continued melting and retreat of the Pine Island Glacier has been breached, the ice's fate remains murky, says glaciologist David Holland of New York University in New York City. That's because glaciologists aren't sure what got the glacial retreat started in the first place, he notes. It wasn't the greenhouse simply warming the ocean, researchers agree. Instead, shifting winds around Antarctica in recent decades may have driven warmer waters up to the ice and dislodged it from its perch on the ridge. But what caused the winds to shift? Global warming? The ozone hole? Random variability? Glaciologists—and policymakers—would like to know.
... which makes Fred Pearce's prediction (which we quoted in Climate Code Red two years ago, page 47) look spot on ...
Another vulnerable place on the West Antarctic ice sheet is Pine Island Bay, where two large glaciers, Pine Island and Thwaites, drain about 40 per cent of the ice sheet into the sea. The glaciers are responding to rapid melting of their ice shelves and their rate of flow has doubled, whilst the rate of mass loss of ice from their catchment has now tripled. NASA glaciologist Eric Rignot has studied the Pine Island glacier, and his work has led climate writer Fred Pearce to conclude that ‘the glacier is primed for runaway destruction’. Pearce also notes the work of Terry Hughes of the University of Maine, who says that the collapse of the Pine Island and Thwaites glaciers — already the biggest causes of global sea-level rises — could destabilise the whole of the West Antarctic ice sheet. Pearce is also swayed by geologist Richard Alley, who says there is ‘a possibility that the West Antarctic ice sheet could collapse and raise sea levels by 6 yards [5.5 metres]’, this century.
So much for 0.8 metres being a risk-averse foundation for sea-level rise planning and policy-making.
And for a fuller discussion on the current research on PIG and recent observations, there is a great overview, Is Pine Island Glacier the Weak Underbelly of the West Antarctic Ice Sheet?" at RealClimate, from November 2009.
David Spratt
24 January 2010
#OtherArticles" id="OtherArticles">Appendix: Other articles from Climate change media to 20 January 2010
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Picks of the week
World's glaciers melting at accelerated pace, leading scientists
say by Suzanne Goldenberg, Guardian, 20 January 2010
From the Alps to the Andes, the world's glaciers are retreating at an accelerated pace - despite the recent controversy over claims by the United Nations' body of experts, leading climate scientists said today.
Climate Denial Industry Blowing Hot Air On Himalayan Glaciers by rendan Demelle, DeSmogBlog, 20 January 2010
The climate denial industry is once again trying to make a huge to-do about a tiny error by the Intergovernmental Panel on Climate Change.
The End of Magical Climate Thinking by Ted Nordhaus and Michael Shellenberger, Foreign Policy, 16 January 2010
One year ago, America's president said he was going to start a green- energy revolution. Here's why the Obama administration failed -- and what needs to come next.
Puzzle me this: climate change theory allows no ice age
Ben Cubby, SMH, 16 January 2010 Christopher Walter, the Third Viscount Monckton of Brenchley, likes riddles.
Energy & innovation
100 Percent Renewable? One Danish Island Experiments with Clean Power
David Biello, Scientific American, January 19, 2010 One small island in Denmark is technically 100 percent powered by sustainable sources of energy. Could the experiment succeed anywhere else?
German tariff cuts to spark solar sector bloodbath
Christoph Steitz and Leonora Walet, Reuters, 15 January 2010 A potential deep cut in feed-in tariffs in Germany will hit solar companies around the world and increases pressure on large players to reduce exposure to the world's largest photovoltaic market.
A Renewable World: Energy, Ecology, Equality (book)
by Herbert Girardet and Miguel Mendonca
Can CO2 Catchers Combat Climate Change?
Samiha Shafy, Spiegel online, 15 January 2010 While nations bicker about who should cut greenhouse gas emissions and by how much, scientists are dreaming up their own solutions to global warming. A German professor has created a filter which extracts more than a thousand times more carbon dioxide from the air than a tree.
Editorial comment: The process seems cheap and has advantages. Ultimately it relies on storing the captured carbon deep underground, which seems to me to still be problematic. The whole process produces a fifth as much Carbon Dioxide as it captures. This would also represent a cost in non-renewable energy.
Politics & policy
UN should be sidelined in future climate talks, says Obama official
Suzanne Goldenberg and John Vidal, Guardian, 14 January 2010 America sees a diminished role for the United Nations in trying to stop global warming after the "chaotic" Copenhagen climate change summit, an Obama administration official said today.
Why it's wrong to preach "climate justice"
Mark Lynas, New Statesman, 14 January 2010 Two wrongs don't make a right -- carbon is not a prerequisite to development.
Can We Talk Sensibly About The ETS Now?
Tessa Toumbourou, New Matilda, 21 January 2010 The climate deadlock offers new hope of scrapping the worst bits of Rudd's CPRS, especially its extreme reliance on worthless carbon "offsets", writes Tessa Toumbourou
Science & impacts
Radical sea defence rethink urged
BBC News, 15 January 2010 Rising sea levels and more storms could mean that parts of at-risk cities will need to be surrendered to protect homes and businesses, a report warns.
If It's That Warm, How Come It's So Damned Cold? (PDF)
James Hansen, Reto Ruedy, Makiko Sato, Ken Lo, 15 January 2010
Arctic permafrost leaking methane at record levels, figures show
David Adam, Guardian, 14 January 2010 Experts say methane emissions from the Arctic have risen by almost one- third in just five years, and that sharply rising temperatures are to blame
AND
Alister Doyle, Reuters, 16 January 2010
Arctic emissions of a powerful greenhouse gas jumped 30 percent in recent years in a worrying hint that global warming might unlock vast stores frozen in permafrost, scientists said on Friday.
Get ready for seven-foot sea level rise as climate change melts ice
sheets
Rob Young and Orrin Pilkey, Yale Environment 360, 15 January 2010 The IPCC's 2007 report missed out the melting of the Greenland and West Antarctic ice sheets which would be the key drivers in dramatic sea level rises.
AND
Memo to IPCC: Please reanalyze ALL of your conclusions about melting
ice and sea level rise.
Joseph Romm, Climate Progress, 18 January 2010 Good news: The Himalayan glaciers will probably endure past 2035. Bad news: If we don't reverse our emissions trend soon, their disappearance is likely to become irreversible before then.
AND
How the Murdoch press got it wrong on the Himalayan big melt (also published on candobetter.org)
Damien Lawson and David Spratt, Crikey, 20 January 2010 Drawing on a January 13 New Scientist story by Fred Pearce reporting on a debate among glaciologists about the IPCC's claim, The Times (UK) and subsequently The Australian and other Murdoch papers have tried to shift from a debate about timing to a questioning of global warming.
AND
Isabel Hilton, The Guardian, 20 January 2010 What's really shocking about research into the glaciers of the Himalayas is how little there has been.
An Ice Shelf the Size of Rhode Island Breaks Up in Just 24 Hours
3 time-lapsed photos show the incredible disintegration of the Filchner ice shelf in Antarctica.
2009 - 2nd hottest year on record while sun is coolest in a century
Skeptical science, 16 January, 2010
The skeptic argument "It's the sun" is both the most used skeptic argument and the most visited page on this website. So with NASA GISS updating the surface temperature record with completed 2009 data, I've updated the comparison between sun and temperature. While 2009 is the second hottest year on record (tied with 2007), solar activity has fallen to its lowest level in over a century.
Psychology, strategy and change
Climate change and its toll on mental health
Joseph Brean, National Post Published: 18 January 2010 Mardi Tindal, the newly elected moderator of the United Church of Canada, returned from last month's climate change summit in Copenhagen with a deep malaise. Not a true clinical depression, but an anxious despair that reduced her to weeping.
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