Arctic death spiral: sea ice passes defacto tipping point

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 risk, I’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 1000 ppm, 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 to 1000 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.

More at the link