Blog Archive

Wednesday, August 10, 2011

Joseph Romm: Arctic Death Spiral: Sea Ice Passes De Facto Tipping Point Thanks to Deniers, Media Blow The Story, Again

Arctic Death Spiral: Sea Ice Passes De Facto Tipping Point Thanks to Deniers, Media Blow The Story, Again

by Joe Romm, Climate Progress, August 9, 2011

Arctic sea ice volume by month in cubic kilometers.  The bottom (black) line is September volume. The plot makes projections with simple quadratic trend lines (details here), which likely oversimplify matters as we approach zero volume (especially for non-summer months).  But reversal of the overall death spiral is highly implausible absent an even more implausible reversal of current climate policies — policies which are promoted by denier disinformation and sustained by media stenography.
The Arctic is all but certain to be virtually ice free within two decades (barring extreme volcanic activity).  I’m happy to make bets with any bloggers, like Andy Revkin, who apparently believe otherwise.
The recent scientific literature makes clear that while that death spiral could theoretically be reversed, it would require policies that climate science deniers have successfully demonized, policies many in the traditional media regularly pooh pooh or undercut.
So we have passed a de facto tipping point, “the critical point in an evolving situation that leads to a new and irreversible development.”  If that wasn’t obvious from observations, then it should have been clear from a December study in Nature widely misunderstood by the media.  That study showed sea ice extent crashing by two thirds by the 2030s and then collapsing to near-zero shortly thereafter — unless we cut global GHG emissions about 60% to 70% almost immediately and have further cuts after that, an implausible assumption the authors never spelled out clearly (as I explain here).
Now comes a new study that has also proven an irresistible source of confusion to both the deniers and the media, “A 10,000-Year Record of Arctic Ocean Sea-Ice Variability—View from the Beach” (subs. req’d).  The news release is as misleading as the Nature article:
The bad news is that there is a clear connection between temperature and the amount of sea ice. And there is no doubt that continued global warming will lead to a reduction in the amount of summer sea ice in the Arctic Ocean. The good news is that even with a reduction to less than 50% of the current amount of sea ice the ice will not reach a point of no return: a level where the ice no longer can regenerate itself even if the climate was to return to cooler temperatures,” [lead author Svend] Funder says.
Huh? How precisely is the climate going to return to cooler temperatures?  It really bugs me when scientists who are very sophisticated in one arena — here, proxy reconstructions of ice coverage of part of the Arctic — exhibit magical thinking in another area.
The best recent models show staggeringly high Arctic warming this century if we stay on our current emissions path (see M.I.T. doubles its 2095 warming projection to 10 °F — with 866 ppm and Arctic warming of 20 °F). Cooling ain’t in the cards.  Quite the reverse.
The Nature article projected a 50% decline in sea ice within 2 decades no matter what we do on emissions — and then total collapse even on a scenario with significant emissions reductions.  As an aside, since that study almost certainly underestimated the rate of sea ice loss — for instance, it ignores black carbon, a major source of ice loss — I tend to think that the actual summer ice loss will be somewhere between what that study projected and the oversimplified quadratic projections in the figure above.
The BBC, which promised better coverage on climate change, failed to deliver this time — as can be seen in its story, “Arctic ‘tipping point’ may not be reached.
NYT opinion blogger Andy Revkin wrote one of the worst pieces in his career, “On Arctic Ice and Warmth, Past and Future,” which quickly became a darling of the hard-core anti-science deniers for these absurd lines:
But even as I push for an energy quest that limits climate riskI’m not worried about the resilience of Arctic ecosystems and not worried about the system tipping into an irreversibly slushy state on time scales relevant to today’s policy debates. This is one reason I don’t go for descriptions of the system being in a “death spiral.”
The main source of my Arctic comfort level — besides what I learned while camped with scientists on the North Pole sea ice — is the growing body of work on past variations* in sea ice conditions in the Arctic. The latest evidence comes in a study in the current issue of Science. The paper, combining evidence of driftwood accumulation and beach formation in northern Greenland with evidence of past sea-ice extent in parts of Canada, concludes that Arctic sea ice appears to have retreated far more in some spans since the end of the last ice age than it has in recent years.
“Not worried about the resilience of Arctic ecosystems“?  Seriously?
Exactly what Arctic ecosystems are going to survive the accelerated warming humans are imposing, warming that will occur at twice the rate of the planet as a whole?  And that is compounded by ocean acidification, which is equally devastating in the Arctic.
Revkin’s wishy-washy “energy quest” can’t stop either of those disasters.  Indeed, Revkin never tells you what CO2 concentrations target he is questing for, but he endlessly criticizes those of us who actually spell out a target, like 450 ppm (or lower) and a path to achieve it.  He dismisses such targets as a “magically safe level of carbon dioxide” — a reductio ad absurdum meant to put him above the fray, allowing him to critique all those trying to avert 800+ ppm — a CO2 level he once told me is where he expects we’ll end up.
Indeed in 2008, he himself quoted Nobelist Sherwood Rowland who thinks we’re headed toward 1,000 ppm [yeah, that is what Dr. Rowland thought in 2008, and most likely he has not changed his mind in the meantime], an unimaginable catastrophe.  Back then he wrote, “Keep in mind that various experts and groups have said risks of centuries of ecological and economic disruption rise with every step toward and beyond 450 parts per million.”  Now, by failing to identify even a range we should aim for, say 400 to 500 ppm or policies that could plausibly keep us near such a range — and worse, by mocking those of us who do — he is effectively endorsing the acceptability of the 800-1,000 ppm range.
The science is clear that human-caused Arctic warming has overtaken 2,000 years of natural cooling, as a “seminal” 2009 Science study found” [see figure below]:
In short, “greenhouse gas emissions are overwhelming the system,” as David Schneider, a visiting scientist at the National Center for Atmospheric Research and one of the co-authors of the 2009 Science article put it.
Oh, but Revkin says he’s “not worried about the system tipping into an irreversibly slushy state on time scales relevant to today’s policy debates.”
Well, NOAA and the National Snow and Ice Data Center (NSIDC) are worried, and unlike Revkin, they have published science to back them up — see NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100.
Figure:  Carbon emission (in billions of tons of carbon a year) from thawing permafrost.
UPDATE:  Revkin tries to claim that I’m “straying into discussions of melting permafrost,” which he claims “is an entirely different issue.”  But it isn’t.  He is the one who wrote that he is “not worried about the system tipping into an irreversibly slushy state on time scales relevant to today’s policy debates.”  The perma-melt NOAA/NSIDC is the “irreversibly slushy state.”  I thought that was obvious.
I have little doubt that the drop in sea ice over the next 10 to 15 years will be a major driver of policy — now that the deniers, with the cover provided by a complacent media, have made serious action this decade unlikely.
The fact is the new study in Science is not terribly germane to what is happening now — as made clear by the study itself and expert quotes Revkin himself prints.
The study looks at one part of the Arctic during the Holocene Climate Optimum (aka the Holocene Thermal Maximum) and finds:
For several thousand years, there was much less sea ice in the Arctic Ocean – probably less than half of current amounts…
The results are based on material gathered along the coast of northern Greenland, which scientists expect will be the final place summer ice will survive, if global temperatures continue to rise.
The problem with the authors’ effort to generalize the results to modern times is that the HCO or HTM — 8,500-6,000 years ago — was utterly different than today.  They write:
The period ~8.5 to 6 ky B.P. marks the Holocene Thermal Maximum (HTM) in this area. Long continuous beach ridges northward along the coast up to 83° N show that this was the southern limit of permanent sea ice, ~1,000 km to the north of its present position. To the north of 83° N, beach ridges are restricted to bays and major river mouths, showing that this coast had permanent sea ice but was within the zone of coastal melt. Coastal melt is determined by local summer temperatures (15), and this indicates that summer temperatures during the HTM in north Greenland were 2-4 °C warmer than now, as elsewhere in this part of the Arctic (17)….
In this exercise, our records would correspond in the model to an Arctic Ocean sea-ice cover in summer at 8 ky B.P. that was less than half of the record low 2007 level.
But the HTM warming wasn’t driven by rapidly-increasingly GHG levels, which have a significant thermal lag — that is, there is a lot more warming in the pipeline today.  Also, today soot, or black carbon, is a major driver of Arctic melt, which means we’re getting melting beyond the warming temperatures from GHGs.
Finally, the HTM warming in the Arctic was driven by conditions that are utterly different than what we have today.  The paragraph above ends citing reference 17, “Holocene thermal maximum in the western Arctic (0–180° W),” which is online here.  It explains:
At the 16 terrestrial sites where quantitative estimates have been obtained, local HTM temperatures (primarily summer estimateswere on average 1.6 +/-0.8 °C higher than present (approximate average of the 20th century), but the warming was time-transgressive across the western Arctic.  As the precession-driven summer insolation anomaly peaked 12–10 ka (thousands of calendar years ago), warming was concentrated in northwest North America, while cool conditions lingered in the northeast.
Note that these are just summer temps and only regionally localized and relative to the average temperature of the last century (not, say, “now,” as the new article asserts).
Now we have warming that is year-round and global and accelerating rapidly.  Revkin himself has two key quotes from experts trying to explain this:
James Overland, Pacific Marine Environmental Laboratory:  “What the authors say is consistent with previous ideas. At the Holocene maximum the orbit was more elliptic and the axis was more tilted. We had very short hot summers and long cold winters. It is not clear which season would win out. A lot of proxies are for summer only, so they slant the data too much for warming. It is hard to get models to be completely sea-ice free during this period, so this paper’s results are consistent. Other papers on erosion of Greenland beaches suggest the same thing. Bottom line is that current and historical sea ice cover is sensitive to changes in the radiation balance.”
Leonid Polyak of the Byrd Polar Research Center at Ohio State University notes that the general climatic and ice situation in the Arctic now appears very different than what prevailed in earlier Holocene warm periods:  “Overall, the early-Holocene situation in the Arctic seems to be very different from the modern one. Now we are having the strongest ice retreat in the Pacific sector and ice pile-up near Greenland – practically the opposite to what Funder’s paper suggests for the early Holocene.”
In short, you can’t draw any lessons from this paper for today.  And that’s without even factoring in the black carbon and thermal lag.
I repeat — we have passed a de facto tipping point.  Yeah, you can devise  a theoretical scenario of emissions reductions that might — might — stabilize the Arctic, but such a scenario is all but impossible in the face of implacable opposition by the deniers and their political allies, and it is precisely the kind of emissions reduction scenario Revkin himself constantly dismisses.
The Arctic is all but certain to be virtually ice free within two decades (barring extreme volcanic activity).  I’m happy to make bets with any bloggers, like Andy Revkin, that the Arctic will have under half the ice it has today by 2020, thus equaling or surpassing the lowest level identified in this Science paper.  The death spiral continues.

No comments: