Graph of the day

Courtesy of Mother Jones, h/t The Dish:

Adapt, Geoengineer, Mitigate (AGM)

Source: National Research Council. 2011. Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia. p.101. Washington, DC: The National Academies Press

So it's time to talk about geoengineering. Like it or not.

The reality that a significant amount of carbon dioxide and methane are going to emerge from melting permafrost seems at last to be making an impression on the popular press (thanks latterly to a recent UN report). The implication, that it is extraordinarily improbable that mitigation alone will be able to limit warming to < 2C above preindustrial, does not seem to have sunk in yet, but the logic is fairly inescapable.

Investigations of climate sensitivity continue to come back with values clustering around 3C/doubling. Based on those values, the total amount of CO2 that can be added to the atmosphere and still leave us with the hope of keeping warming below the 2C target is about 1,000 gigatons or a trillion tons. Total CO2e emissions to date are between 500 and 600 gigatons. Permafrost emissions by 2200 are estimated to be between 246 to 415 gigatonnes. Take the midpoints of both ranges and add them together and you get 880 gigatons. Right now the world is adding to that figure at a rate of 30 gigatons of carbon dioxide per year, plus sundry other GHGs.

Even if you could instantly cut GHG production by 90%, you'd still cross the threshold within 40 years or so.  Any sort of a realistic program -- and in that I include a WWII-style crash program to cut emissions, consuming a significant chunk of the planet's GDP over the next few decades -- would come nowhere close to meeting the trillion ton target.

Taking the most likely case -- that scientists' warnings continue to fall on deaf ears for at least a half a decade -- we will commit ourselves absolutely in four to five years -- perhaps less, if the world economy grows at a brisk pace.

It's possible, of course, to stick with the party line despite the inevitability of crossing the trillion-ton mark. Emission cuts as fast as possible; adaptation; and hold on to something, because the 21st century is looking like a bumpy ride. But it is more in the spirit of climate realism to face the facts honestly and, where necessary, change our strategy.

What are those facts? Fact number one: carbon-cycle feedbacks will put the 2C target out of reach through mitigation alone. Fact two: the severity of the climate impacts we are seeing at 0.8C above preindustrial suggests the 2C is a hard target. Two and a half times the warming we have seen to date is already, probably, outside any reasonable boundary of "safe" temperatures. Fact three: the Arctic permafrost is not the only game in town. There is also carbon under Antarctica. There are methyl hydrates. There is carbon locked up in the Amazon and other forests vulnerable to die-back.

If you take the 2C limit seriously, you have to consider that the time may be approaching where we will need geoengineering as a bridge to lower levels of GHGs.

Geoengineering has a bad reputation. People fear it as a quick fix, a barrier to the changes we need, and a long walk off a short pier into the Bay of Unintended Consequences. It has the potential to be all of those things. But it seems increasingly unlikely that we will get through the next two centuries in one piece without it.

The AGM strategy has three elements:

Adapt: Prepare our defenses and infrastructure for multi-meter sea level rise and the storms of the 21st century. Prepare our water resources for droughts, salinization, and flooding. Prepare our emergencies services, diversify our food crops, improve the robustness (and efficiency) of our infrastructure.

Geoengineer: Start planning with small-scale tests now; larger-scale tests as soon as feasible; infrastructure for large-scale deployment as soon as we have a workable technology or set of technologies. Then set a hard upper limit well back from the 2C boundary -- like 1.5C, or at the first sign of a catastrophe like massive methyl hydrate degassing. At 1.5C over preindustrial, geoengineering kicks in.

Mitigate: Agreement to severe and ongoing cuts in GHG emissions between a few large powers, with serious diplomatic and economic arm-twisting as necessary to enlist the rest of the world. Our goal should be to get back to 350ppm CO2e

Could wildly successful geoengineering decrease the pressure for an agreement on serious mitigation? Sure it could. But you have to ask yourself if you believe the science.

If you do believe the science, and understand that as we approach 2C our civilization and most of the species we share the earth with are in mortal danger, then while that perverse incentive matters, it can't be paramount, any more than the fear that people will eat too much and not exercise is a reason to not put a heart attack survivor on blood pressure and cholesterol-lowering medications. Yes, they have side effects. Yes, they are in some respects an artificial compensation for a failure in self-control. Nevertheless, letting the patient drop dead is a bad option. Better to use the artificial support, and continue to campaign for the lifestyle changes.

xkcd on the election

Randall nails it as usual:

Bookmark it if you haven't

Could we see a triple-dip La Nina?

Lately ENSO has been teasing us with a halting, stop-go flirtation with El Nino conditions. It certainly seems like we're due, given the preceding double-dip La Nina, something which, as I wrote last year, is already an unusual event. But then there's this:

Really? Another La Nina? How weird is that?

Actually it has never happened since NOAA started keeping records. Sixty years ago. Talk about your global weirding.

NOAA still rates a weak El Nino as more likely than a return to La Nina conditions. But it's modestly amazing to me that a triple-dip is even a realistic possibility. Come what may, eventually we're going to see a strong El Nino again. The longer we wait, the more profound and record-shattering the ensuing temperatures are likely to be.

Gulf Stream destabilizing methyl hydrates

Thus Nature:

The Gulf Stream is an ocean current that modulates climate in the Northern Hemisphere by transporting warm waters from the Gulf of Mexico into the North Atlantic and Arctic oceans^{1, 2}. A changing Gulf Stream has the potential to thaw and convert hundreds of gigatonnes of frozen methane hydrate trapped below the sea floor into methane gas, increasing the risk of slope failure and methane release^{3, 4, 5, 6, 7, 8, 9}. How the Gulf Stream changes with time and what effect these changes have on methane hydrate stability is unclear. Here, using seismic data combined with thermal models, we show that recent changes in intermediate-depth ocean temperature associated with the Gulf Stream are rapidly destabilizing methane hydrate along a broad swathe of the North American margin. The area of active hydrate destabilization covers at least 10,000 square kilometres of the United States eastern margin, and occurs in a region prone to kilometre-scale slope failures. Previous hypothetical studies^{3, 5} postulated that an increase of five degrees Celsius in intermediate-depth ocean temperatures could release enough methane to explain extreme global warming events like the Palaeocene–Eocene thermal maximum (PETM) and trigger widespread ocean acidification⁷. Our analysis suggests that changes in Gulf Stream flow or temperature within the past 5,000 years or so are warming the western North Atlantic margin by up to eight degrees Celsius and are now triggering the destabilization of 2.5 gigatonnes of methane hydrate (about 0.2 per cent of that required to cause the PETM). This destabilization extends along hundreds of kilometres of the margin and may continue for centuries. It is unlikely that the western North Atlantic margin is the only area experiencing changing ocean currents^{10, 11, 12}; our estimate of 2.5 gigatonnes of destabilizing methane hydrate may therefore represent only a fraction of the methane hydrate currently destabilizing globally. The transport from ocean to atmosphere of any methane released—and thus its impact on climate—remains uncertain.

A number of outlets have picked up on this story, and it's easy to see why. This is another classic we-thought-it-would-take-thousands-of-years moment. In recent years methyl hydrate deposits in the Arctic, and especially the shallow deposits in the East Siberian Arctic Shelf, have grabbed the spotlight. Another recent study made headline when it warned of large methane deposits under Antarctica. It seemed that methane was on the move North and South, and the poles grabbed most of the popular attention. But:

Methane hydrates are over over the place. Including places in the ocean dramatically warmed by shifting ocean currents. So there's that.

Key points from the study include:

1. Methyl hydrate deposits are being destabilized by warming oceans right now.
2. We don't know how much of this carbon will make it into the atmosphere, vs contributing to the acidification of the oceans.
3. The study looked at part of the North American coastline, but this process is likely unfolding in other parts of the world as well.
4. Reports of the death of the clathrate gun hypothesis have been greatly exaggerated. This is only one of many recent studies to illustrate that carbon-cycle feedbacks have the potential to add large amounts of greenhouse gases to the atmosphere. How fast? Not overnight, but not necessarily over thousands of years, either.
5. With vulnerable carbon stores in the Arctic, the Antarctic, and on the continental shelves in between, it is becoming painfully clear that anthropogenic global warming is a game of Russian roulette played with a semiautomatic.

Climate deniers losing the argument

Americans’ Global Warming Beliefs and Attitudes in September 2012

Highlights

• Americans’ belief in the reality of global warming has increased by 13 percentage points over the past two and a half years, from 57 percent in January 2010 to 70 percent in September 2012. At the same time, the number of Americans who say global warming is not happening has declined nearly by half, from 20 percent in January 2010 to only 12 percent today.

• For the first time since 2008, more than half of Americans (54%) believe global warming is caused mostly by human activities, an increase of 8 points since March 2012. Americans who say it is caused mostly by natural changes in the environment have declined to 30 percent (from 37% in March).

• A growing number of Americans believe global warming is already harming people both at home and abroad. Four in ten say people around the world are being harmed right now by climate change (40%, up 8 percentage points since March 2012), while 36 percent say global warming is currently harming people in the United States (up six points since March).

• In addition, they increasingly perceive global warming as a threat to themselves (42%, up 13 points since March 2012), their families (46%, up 13 points), and/or people in their communities (48%, up 14 points). Americans also perceive global warming as a growing threat to people in the United States (57%, up 11 points since March 2012), in other modern industrialized countries (57%, up 8 points since March), and in developing countries (64%, up 12 points since March).

• Today over half of Americans (58%) say they are “somewhat” or “very worried” - now at its highest level since November 2008.

• For the first time since 2008, Americans are more likely to believe most scientists agree that global warming is happening than believe there is widespread disagreement on the subject (44% versus 36%, respectively). This is an increase of 9 percentage points since March 2012.

This is a welcome reminder that the climate blogosphere is a tiny, tiny community, and the irrational, unpersuadable right-wing ideologues who relentlessly seek domination over it do not reflect the broader, disengaged public. Nor is the public responding to pro-science perspectives. If I had to guess, I'd say they are simply responding to the evidence that they are seeing with their own eyes.

Three papers on the Antarctic ice

There is a lot of carbon under that ice.

Potential methane reservoirs beneath Antarctica Wadham et al (2012)

Abstract: Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon¹. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick² and an estimated 21,000 petagrams (1 Pg equals 10¹⁵ g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model³ and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.

That ice is melting faster than we thought it would.

Dynamics of the last glacial maximum Antarctic ice-sheet and its response to ocean forcing -- Fogwill et al (2012)

Abstract: Retreat of the Last Glacial Maximum (LGM) Antarctic ice sheet is thought to have been initiated by changes in ocean heat and eustatic sea level propagated from the Northern Hemisphere (NH) as northern ice sheets melted under rising atmospheric temperatures. The extent to which spatial variability in ice dynamics may have modulated the resultant pattern and timing of decay of the Antarctic ice sheet has so far received little attention, however, despite the growing recognition that dynamic effects account for a sizeable proportion of mass-balance changes observed in modern ice sheets. Here we use a 5-km resolution whole-continent numerical ice-sheet model to assess whether differences in the mechanisms governing ice sheet flow could account for discrepancies between geochronological studies in different parts of the continent. We first simulate the geometry and flow characteristics of an equilibrium LGM ice sheet, using pan-Antarctic terrestrial and marine geological data for constraint, then perturb the system with sea level and ocean heat flux increases to investigate ice-sheet vulnerability. Our results identify that fast-flowing glaciers in the eastern Weddell Sea, the Amundsen Sea, central Ross Sea, and in the Amery Trough respond most rapidly to ocean forcings, in agreement with empirical data. Most significantly, we find that although ocean warming and sea-level rise bring about mainly localized glacier acceleration, concomitant drawdown of ice from neighboring areas leads to widespread thinning of entire glacier catchments—a discovery that has important ramifications for the dynamic changes presently being observed in modern ice sheets.

When that ice melted previously, global carbon dioxide levels rose dramatically over only two hundred years.

Abrupt change in atmospheric CO2 during the last ice age – Ahn et al. (2012)
Abstract: “During the last glacial period atmospheric carbon dioxide and temperature in Antarctica varied in a similar fashion on millennial time scales, but previous work indicates that these changes were gradual. In a detailed analysis of one event we now find that approximately half of the CO2 increase that occurred during the 1500-year cold period between Dansgaard-Oeschger (DO) events 8 and 9 happened rapidly, over less than two centuries. This rise in CO2 was synchronous with, or slightly later than, a rapid increase of Antarctic temperature inferred from stable isotopes.”
Citation: Ahn, J., E. Brook, A. Schmittner, and K. J. Kreutz (2012), Abrupt change in atmospheric CO2 during the last ice age, Geophys. Res. Lett., doi:10.1029/2012GL053018.

Comment: This is all very new science, but these three very different papers with different subjects and different methods seem together to suggest a coherent narrative; ocean warming rapidly triggers widespread decay of the Antarctic ice sheets, which uncovers significant amount of carbon. That carbon makes its way into the atmosphere, in amounts significant enough to warm the climate further.

The Arctic permafrost feedback appears (to an outsider, like me) to be gaining widespread acceptance as a significant contributor to global warming both in the near term (the next century) and in the longer term (a few centuries.) Now we are trying to nail down the scale of the feedback. Meanwhile, we are starting to get some science that suggests a similar carbon-cycle feedback could unfold in the South, scale and speed unknown.