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.

Committed warming

Andrew Weaver, the faculty author on Nature Geosciences' new paper on the Arctic permafrost carbon feedback (not to be confused with the new paper implying the risk of a catastrophic Antarctic carbon feedback), is talking about the paper from his perch at the Huffington Post. He offers his take on the committed warming in the pipeline:

Instrumental records have clearly revealed that the world is about 0.8°C warmer than it was during pre-industrial times. Numerous studies have also indicated that as a consequence of existing levels of greenhouse gases, we have a commitment to an additional future global warming of between 0.6 and 0.7°C. Our analysis points out that the permafrost carbon feedback adds to this another 0.4 to 0.8°C warming. Taken together, the planet is committed to between 1.8 and 2.3°C of future global warming -- even if emissions reductions programs start to get implemented.

So <+2C is off the table, unless we geoengineer (Planet 3.0 is revisiting the subject now). So there's that.

The last time the Earth was two degrees warming was the mid-Pliocene. That was about three million years ago. So common sense would suggest we prepare for a world that looks similar to the mid-Pliocene. Well . . .

* Sea levels were between 15m and 25m higher.
* The WAIS repeatedly melted back (repeatedly), potentially uncovering large carbon reserves.
* The Arctic was 10C-20C hotter than the present day (suggesting that while our climate models can't fully reproduce the degree of Arctic amplification we observe today, it's likely to be a real and persistent feature of the climate system.)

It will be interesting to see how cost/benefit estimates change once this permafrost carbon feedback is "priced in" to economic models of climate change. On the one hand, damages will increase. On the other hand, the differences between BAU and intensive mitigation scenarios will decrease, because the permafrost feedback will cause less warming in a hotter world, and more warming in a cooler world. Just to give a simple illustration, consider a carbon feedback that adds 100ppm of CO2 to the atmosphere. Then overlay that atop two scenarios:

* Aggressive mitigation -- 450ppm CO2
* BAU -- 800ppm CO2

Those numbers go into this equation:

 Where C(0) is preindustrial CO2 (280ppm), and C is 450ppm and 800ppm, respectively. Do that and we get a forcing of 2.5W/m^2 vs 5.6W/m^2. But look what happens when we add the permafrost carbon:

* Aggressive mitigation -- (450 + 100=) 550ppm CO2 = 3.6W/m^2
* BAU -- (800 + 100=) 900ppm CO2 = 6.2W/m^2

Both forcings have increased, but the mitigation scenario has increased far more, making the difference between mitigation and carbocide somewhat smaller: 2.6W/m^2 compared to 3.1W/m^2.

It's not a huge difference, but it narrows the difference between action and inaction, and least in terms of forcing. At the same time all scenarios get more expensive and destructive. It'll be interesting to see which effect is stronger.

Permafrost carbon feedback update

There's a new paper out:

Significant contribution to climate warming from the permafrost carbon feedback

Permafrost soils contain an estimated 1,700 Pg of carbon, almost twice the present atmospheric carbon pool¹. As permafrost soils thaw owing to climate warming, respiration of organic matter within these soils will transfer carbon to the atmosphere, potentially leading to a positive feedback². Models in which the carbon cycle is uncoupled from the atmosphere, together with one-dimensional models, suggest that permafrost soils could release 7–138 Pg carbon by 2100 (refs 3, 4). Here, we use a coupled global climate model to quantify the magnitude of the warming generated by the feedback between permafrost carbon release and climate. According to our simulations, permafrost soils will release between 68 and 508 Pg carbon by 2100. We show that the additional surface warming generated by the feedback between permafrost carbon and climate is independent of the pathway of anthropogenic emissions followed in the twenty-first century. We estimate that this feedback could result in an additional warming of 0.13–1.69 °C by 2300. We further show that the upper bound for the strength of the feedback is reached under the less intensive emissions pathways. We suggest that permafrost carbon release could lead to significant warming, even under less intensive emissions trajectories.

Between 68-508 Pg, or 68-508 billion tons of carbon, or, if it all comes out as CO2 (and you'd better hope it does, more or less), 255 to 1,910 billion tons of CO2. For comparison, human emissions in 2010 amounted to 9.1 billion tons of carbon. This feedback could be thought of like continuing on with our current emissions for between seven to fifty-five years, except we don't get any choice in the matter.

This is higher than most of the previous estimates I've seen. Koven et al (2011), for example, estimated 55-69 Pg C of carbon. There are a number of other estimates from a variety of sources using a number of methods. From "Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle":

Risk assessments, based on expert opinion, estimated that up to 100 Pg C could be released from thawing permafrost by 2100 (Gruber et al. 2004). On the basis of laboratory incubation experiments and estimated C stocks, Dutta and colleagues (2006) calculated a potential release of about 40 Pg C over four decades if 10% of the C stock frozen in deep soils in Siberia thawed to 5°C. Tarnocai (2006) estimated that 48 Pg C could be released from Canadian permafrost over this century if the mean annual air temperature increased by 4°C. Model predictions incorporate changes in vegetation and other disturbances, as well as C release from permafrost, to determine the net effect of climate warming. Results for Alaska and for the circumpolar region predict the addition of up to 50 to 100 Pg C to the atmosphere by the end of the century, depending on the particular model scenario (Stieglitz et al. 2003, Zhuang et al. 2006).

In other bad news from the Arctic permafrost, Vonk et al (2012) found breakdown of Siberian "Yedoma" permafrost dumping ten times as much CO2 into the Arctic ocean compared to prior estimates.

All of this has, for me, a distinct hint of the Arctic sea ice narrative, to the tune of "Oh-yes-change-will-come-we-see-it-in-the-record-a-few-thousand-years-maybe-OK-maybe-faster-OK-now-we're-getting-good-direct-measurements-could-be-an-issue-in-a-century-or-two-OK-wait-what-WHATTHEHELLISTHAT?"

The analogy is hardly even an analogy at all. The permafrost most at risk, after all, is just another species of Arctic ice. And it should be as clear as crystal that the Arctic is changing faster than experts thought possible just a few years ago. The bits of it impregnated with thousands of gigatonnes of carbon are no exception. Is it a methane bomb, a carbon bomb? It doesn't need to be. When the house is on fire, everything burns.

The Antarctic carbon feedback: a worst case scenario

It's the single study to end all single studies:

The researchers estimate that 50 per cent of the West Antarctic Ice Sheet (1 million km2) and 25 per cent of the East Antarctic Ice Sheet (2.5 million km2) overlies preglacial sedimentary basins, containing about 21,000 billion tonnes of organic carbon.

If this carbon proves to be vulnerable in the way we now think the northern permafrost carbon is vulnerable, it will mean we could soon be literally incapable of stabilizing the climate without geoengineering.

The reason is very simple.  Based on the experience of the Eocene (above), at between 3 and 4 degrees above preindustrial, the Antarctica ice pack can be expected to melt completely (of the course question of exactly what temperature will lead to the deglaciation of Antarctica is a complex scientific question, while the above is an eyeballed guesstimate; see below). If these researchers are right, that will gradually release 21,000 gigatons of carbon.

So let's get down to brass tacks. The carbon is divided between the larger East Antarctic Ice Sheet and the more vulnerable West Antarctic Ice Sheet:

The researchers estimate that 50 per cent of the West Antarctic Ice Sheet (1 million km2) and 25 per cent of the East Antarctic Ice Sheet (2.5 million km2) overlies preglacial sedimentary basins, containing about 21,000 billion tonnes of organic carbon.

Experts place the chances of for the beginning of a total collapse of the WAIS in the next 200 years at upwards of 5%. Estimates of how long such a collapse would take to reach completion range from 300 to 1600 years. The temperature that would trigger that collapse is thought to be somewhere between +1C and +5C compared to 1990 temperatures (2).

Suppose that happened, and, since that's a fairly pessimistic assumption, let's throw in a couple of optimistic assumptions: the EAIS contributes nothing significant, and the northern permafrost and methyl hydrates contribute nothing.

The proportion of the trapped carbon under the WAIS is 4/9 of the total of 21,000 gigatons (about 9,300 gigatons) (1). If the WAIS melts, what proportion of that carbon will enter the atmosphere? Some will obviously remain locked a carbon sink that will develop as the continent warms. Suppose only 60% or so, 6,000 gigatons, ends up in the atmosphere.

A couple hundred billion tons of that will be methane; ignore it. The trapped methane has figured prominently in the news accounts about this research, but compared to the staggering amount of carbon under the ice, most of which would enter the atmosphere as carbon dioxide and the rest of which would be oxidized to carbon dioxide after a brief stint as methane, the news that we have a southern methane time bomb to go with the Arctic one is merely a footnote.

Suppose significant outgassing of the carbon under the WAIS starts in about a hundred years and takes two hundred years to run to completion. Six thousand gigatons over two hundred years is 30 gigatons of carbon per year (on average). By way of comparison, total fossil fuel emissions are running at about 7 gigatons per year:

Source

Thirty gigatons a year is about what the human race is expected to produce at the end of the century is the world economy grows rapidly despite our making no effort to rein in our emissions:

Source

The effect of 6,000 gigatons of carbon entering the atmosphere would be an extinction-level event. One part per million of atmospheric CO2 is equivalent to 2.13 gigatons of carbon. Assuming a 50% airborne fraction (which is incredibly optimistic) 6,000 tons of carbon entering the atmosphere would raise the CO2 concentration by about 1,400ppm. In a worst case in which the carbon sinks finally give up the ghost, the rise is 2,800ppm. Supposing we were at that point at 800ppm and +4C, that would quickly take us to +8C with the EAIS adding its share soon after.

You would be looking at centuries of further warming independent of human emissions -- leading to an increasingly inhospitable climate even if economic collapse reduced the anthropogenic contribution significantly.

There is a large distance between the publication of this one study and a solid scientific case for an Antarctic carbon bomb. The steps along that road are, roughly:

1. Are the authors correct about the scale of the buried carbon?
2. Are the authors right about the distribution of that carbon, specifically about a heavy concentration of it under the most vulnerable part of the ice sheet?
3. Will that ice sheet decay significantly over the next few centuries?
4. If the ice sheet decades, what proportion of the buried carbon will make its way into the atmosphere?
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1. "Potential methane reservoirs beneath Antarctica"  J. L. Wadham, S. Arndt, S. Tulaczyk, M. Stibal,  M. Tranter, J. Telling, G. P. Lis, E. Lawson, A. Ridgwell, A. Dubnick, M. J. Sharp, A. M. Anesio & C. E. H. Butler.  Nature 488, 633–637 (30 August 2012) -- abstract.
2. "The Future of the West Antarctic Ice Sheet: Observed and Predicted Changes, Tipping Points, and Policy Considerations" -- full text.
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UPDATE: Round up from around the interwebs.

 "Potential New Methane Risk in Antarctica" -- SustainableBusiness.com News

"Antarctica’s Hidden Carbon Stores Pose Warming Risk in Study" -- Bloomberg

“There’s a potentially large pool of methane hydrate in part of the Earth where we haven’t previously considered it,” Wadham said in a telephone interview. “Depending on where that hydrate is, and how much there is, if the ice thins in those regions, some of that hydrate could come out with a possible feedback on climate.”

"Large methane reservoirs suggested beneath Antarctic ice sheet" -- phys.org

 "Antarctic Methane: A New Factor in the Climate Equation" -- Climate Central

Wadham and her co-authors took soil samples from the margins of glaciers in both Antarctica and Greenland. “We spent a couple of years chain-sawing out sediments frozen into the bottom of the ice,” she said, adding with a connoisseur’s judgment, “They were very nicely preserved.”

They hauled the samples back to the lab and allowed them to thaw under carefully controlled, oxygen-deprived conditions where oxygen-hating, methane-belching bacteria known as methanogens could do their work — assuming they were there. And sure enough, the soil began producing methane.

The same thing should presumably be happening underneath Antarctica’s ice, where heat percolating from the depths of the Earth have prevented sediments from ever having frozen.

A new way to assess permafrost

Airborne electromagnetic imaging of discontinuous permafrost – Minsley et al. (2012)

H/t you know who. This airborne survey does not tell us -- yet -- about permafrost melting, since it only reflects a single point in time. But repeated annually, it could become an indispensable record of the evolving (read: melting) carbon storage lockers of the North.

I wonder if similar methods have been/could be used in the shallow waters of the East Siberian Arctic Shelf? They say they got data down to 100m -- parts of the ESAS are considerably shallower than that.

The Anna Karenina scenario

Every happy family is alike; every unhappy family is unhappy in its own way.

Leo Tolstoy, Anna Karenina

Apropos of the Anna Karenina Principle, how many things would have to go right for climate change to be merely an expensive annoyance (or one human problem among many), rather than a planetary disaster?

First, we need continued rapid economic growth. Even in the best case, dealing with the impacts of global warming -- drought, sea level rise, heat waves, extreme weather events -- between now and 2100 or 2200 will require resources we don't have today. Without continual economic growth, even most optimistic global scenarios offer certain disaster.

Stern Review

 Five percent of 2100's projected GDP is over 40% of our GDP today -- an impossible burden that would lead to global impoverishment.

The assumption of continued economic growth is a reasonable one, as the world's economy has been on an upward trend for many years:

Nevertheless, continued rapid economic growth is not inevitable, and should be ranked as one of the requirements in realizing the Anna Karenina scenario. Wars, a global depression, unrelated natural disasters, and climate change itself could all compromise this pillar of futurists everywhere.

It is necessary but not sufficient that climate sensitivity prove to be on the low end of estimates. With a climate sensitivity of 3C, and a BAU pathway of 1000ppm CO2 equivalent (1), we can expect +4-6C of warming, which would wipe out most forms of life on earth.

Extract from p. 42 of Technical Summary of IPCC WGIII Fourth assessment Report (2007)

Reasonable people trying to strike a middle course between "alarmism" and "skepticism" will often say that climate change may not be a big deal, but we should protect ourselves from the possibility that climate sensitivity is high. This is well-intended, but a wrongheaded oversimplification. The reality is that while five degrees and onward is a planetary catastrophe under almost any set of assumptions you chose does not mean that 2-3 degrees is an expensive but manageable problem. A high total temperature rise is game over; a low total temperature rise still requires many other things to go right (2).

Sea level rise is presently estimated at between 0.5m to 2.0m between now and 2100. It needs to be closer to 0.5m to avoid the loss of huge numbers of human settlements to the sea. We must hope that the Greenland ice sheet and the WAIS respond very slowly to warming and are largely incapable of responding on a decadal scale. Of course other ice sheets, such as the less-popular sibling of the West Antarctic ice sheet, the East Antarctic ice sheet, must not have any nasty surprises in store.

Agriculture will have to prove highly resistant to climate shocks. Varying the type of crops and making efficient irrigation broadly available while avoiding massive losses to pests, diseases, and extreme precipitation.

We cannot afford to lose the Amazon (as is expected) or the boreal forests: the Anna Karenina scenario requires they resist warming and there is no massive die-off that would turn the terrestrial biosphere into a net source of carbon. That would insure catastrophic long-term warming.

No Arctic warming tipping points.

Healthcare technology and delivery systems will have to advance faster than the spread of tropical diseases north and south. Efficient building designs and/or air conditioning will need to be available to rich and poor alike to avoid millions of deaths from the direct thermal effects alone.

Permafrost melting will need to release its stored carbon slowly, and overwhelmingly as carbon dioxide and only a small amount as methane. Methyl hydrates need to stay put, or leak out only very slowly.

Political systems will have to prove highly resilient and adaptive. They will have to respond to the escalating climate harms with aggressive long-term adaptation, and not make things worse with panic responses like hoarding, protectionism, or conflicts over migration, borders, or resources. As the Economist cogently put it:

I feel fairly comfortable arguing that a modern economy can handle the stresses of climate change reasonably well; economies are built to handle big change. I feel very nervous about the ability of various political systems to survive temperatures unprecedented in human history. Many political systems rely explicitly on stability to survive, and even those capable of handling climate impacts may struggle to handle the knock-on effects of climate impacts on their more vulnerable neighbours. And as political systems are disrupted, it will become more difficult to sustain growth.

This is a partial list. There are impacts I haven't covered; there are certain to be impacts no one has yet guessed at.

The nasty aftertaste of a clear-eyed look at the possibilities is this: even if everything goes right -- if humanity holds the winning climate lottery ticket and none of the terrible things come to pass, or happen only in a blunted and delayed form, and only (in large part) after we are all healthier and wealthier and wiser than we are today: even so, in the best of all possible worlds, global warming will be an expensive destructive mess than will drag on for thousands of years, making the impoverishment of the natural world and disruption of the benign Holocene climate our civilization's permanent legacy.

Most economic analyses assume all these good things happen and neglect, not out of malice but due to the limitations of their science, most of the horrible disasters climate scientists think are possible -- in some cases likely. Even so, the benefits of slowing climate change outstrip the costs in virtually every economic analysis out there.

One of my least favorite lukewarmer fallacies is the concept of "no regrets" policies -- that we should push ahead with policies that can be sold to the right wing as energy independence or job creation or whatever appeals to those in denial of the science. This is an asinine idea. Climate change is real. You don't get to smart policy by agreeing to disagree on critical scientific facts pertaining to the future of human civilization. Here's the truth; aggressive emissions cuts are the true no-regrets strategy. Uncertainty in climate change lies between bad and worse. The benefits range from saving trillions of dollars and millions of lives, on the low side, to averting planetary catastrophe.

_______________________________________________

1) Meaning a forcing caused by human activities similar to change the level of CO2 to 1000ppm, comprised mostly of CO2 but also with contributions from methane, NO, CFCs, and land use changes.

2) The best analysis of the economic implications of a "fat tail" probability of climate catastrophe is "On modeling and interpreting the economics of catastrophic climate change" (2009) by Martin L. Weitzman, the undisputed expert in this area (400+ citations for that paper alone in less than three years). He wisely make the limitations of climate sensitivity highly explicit:

There are so many sources of uncertainty in climate change that a person almost does not know where or how to begin cataloging them. For specificity, I focus on the uncertainty of so-called "equilibrium climate sensitivity." This is a relatively well-defined and relatively well-studied example of known unknowns, even if the uncertainties themselves are uncertain. However, it should be clearly understood that under the rubric of "equilibrium climate sensitivity" am trying to aggregate together an entire suite of uncertainties, including some non-negligible unknown unknowns. So climate sensitivity is to be understood here as a prototype example or a metaphor, which is being used to illustrate much more generic issues in the economics of highly uncertain climate change.

Five things I learned in 2011

1. Trees matter. A lot. They sequester more carbon than we thought; they generate cooling aerosols in their own right. We could do a lot to slow the advance of global warming if we decide to stop reducing forests in extent and start intensive reforestation.

2. The howls of outrage from deniers in the blogosphere in response to an argument vary in direct proportion to how effective that argument is with the broader public. There is a scientific consensus, and in many respects, the science is settled. The global is warming, and humans are the cause. Many deniers or "skeptics" get their funding from fossil fuel companies, exaggerate their qualifications, and misrepresent their results. This is simple stuff to those of us that live and breath this stuff, and deniers try to discourage us from making this arguments with howls of rage and jeering contempt. But they are not the people we need to convince, and the people we do need to convince -- the broader disengaged public -- these are powerful messages that should be underscored. Deniers know they are powerful, which is why they try and silence them.

3. Methane and CO2 release from the North (permafrost and methyl hydrates) could be apocalyptic in its effects. But the significance of this is undercut by the fact that the BAU pathway will almost certainly be apocalyptic in its effects. A lot of carbon is going to come out of those frozen deposits, but having studied it a fair bit this year, this quote from Raymond T. Pierrehumbert most closely reflects my own layperson's view:

But the clathrate release problem is in a rather different category from the runaway greenhouse issue. It has to be seen as just one of the many fast or slow carbon catastrophes possibly awaiting us, in a system we are just groping to understand. The models of destabilization are largely based on variants of diffusive heat transport, but the state of understanding of slope avalanches and other more exotic release mechanisms is rather poor — and even if it turns out that rapid methane degassing isn’t in the cards, you still do have to worry about those several trillion metric tons of near-surface carbon and how secure they are. It’s like worrying about the state of security of Soviet nuclear warheads, but where you have no idea what kind of terrorists there might be out there and what their capabilities are — and on what time scales they operate.

Or to put it another way: what would be the state of the climate today if this carbon didn't exist? Call that scenario one:

On a BAU pathway, we face mass extinctions, tremendous human suffering, and unpredictable feedbacks that could greatly accelerate climate change, including ice loss, glacier melt, forest fires, changes in ocean currents, and other known and unknown shifts in the climate and the biosphere.

With intensive mitigation, many of the same problems await us, but will hopefully develop more slowly, over several centuries, blunting the impact somewhat and giving us an opportunity to reverse some of the effects. We still have to worry about unpredictable feedbacks that could greatly accelerate climate change, including ice loss, glacier melt, forest fires, changes in ocean currents, and other known and unknown shifts in the climate and the biosphere, but forcing the system less intensely will, logically, reduce the risk.

Now add the carbon back in:

On a BAU pathway, we face mass extinctions, tremendous human suffering, and unpredictable feedbacks that could greatly accelerate climate change, including ice loss, glacier melt, forest fires, changes in ocean currents, release of methane and CO2 from permafrost and methyl hydrates, and other known and unknown shifts in the climate and the biosphere.


With intensive mitigation, many of the same problems await us, but will hopefully develop more slowly, over several centuries, blunting the impact somewhat and giving us an opportunity to reverse some of the effects. We still have to worry about unpredictable feedbacks that could greatly accelerate climate change, including ice loss, glacier melt, forest fires, changes in ocean currents, release of methane and CO2 from permafrost and methyl hydrates, and other known and unknown shifts in the climate and the biosphere, but forcing the system less intensely will, logically, reduce the risk.

In isolation, the potential for destabilization of this buried carbon would be a looming global catastrophe. But as it is, it becomes one aspect of a global catastrophe already in progress. That's how I see it, anyway.

4. Climate deniers represent a hard fringe of the American right; climate deniers in the blogosphere are an even smaller and more radicalized sub-group. Their views are not only more extreme than the large minority of the public that doubts the science of climate change, or the majority that is not ready to pay a significant price to combat climate change: they are fundamentally different in their outlook. You can see this in the opinion polls; you can see it in the comments and posts they make, in which a extreme anarcho-libertarianism features prominently. This ideology is totally unknown and would be bizarre to most American conservatives; to climate deniers it is practically conventional wisdom. Note also the amazing prevalence of what can only be described as the mentally ill, suffering from delusions that demonstrate grandiosity, paranoia, loose associations, and flight of ideas.

We can win the undecided middle to our side; there is evidence that this is already happening. We do it not by trying to win over or placate deniers, nor by trying to bait them. We win by telling the truth in a clear, simple, understandable way, by being less crazy and more normal, with the caveat that part of being normal is reacting strongly to people who attack hysterically and dishonestly.

5. Even as the overall picture continues to be grim, I found some of the research I came across this year comforting. This is turn reassures me that my filters, such as they are, are not the industrial-strength blast shields one often notes in one's opponents, but can easily overlook in oneself.

Although I remain very concerned about agriculture, I was happy to see that models that incorporated varying the type of crops and where they are sowed found a less severe impact from warming. Some crops will benefit from a CO2 fertilization effect.

Since warming over the last couple of decades has run at about 0.14-0.17C/decade, versus slightly more, 0.18-0.21C, as we would expect from the bulk of the models, the cheerful possibility exists that short-term climate sensitivity is a little lower than we thought, 2-3C instead of 3C-4C (possibly because the aerosol forcing is on the high side). So while the consequences of climate change, like glacier melt, continue to mostly run ahead of the models, it is hopeful that temperatures are running slightly behind. Of course, even a warming of 0.05C/decade or 0.10C/decade would be incredibly fast in geological terms and very dangerous. To see the danger we need only look at the response of the climate and the natural world. Still, better to be warming a little slower than we expected than a little faster.

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What did you learn in 2011?

NYTimes: As Permafrost Thaws, Scientists Study the Risks

The Times hit it out of the park with this one. They covered the major points of the science, sketched how our understanding has changed, and provided real numbers for the estimated impact:

For now, scientists have many more questions than answers. Preliminary computer analyses, made only recently, suggest that the Arctic and sub-Arctic regions could eventually become an annual source of carbon equal to 15 percent or so of today’s yearly emissions from human activities.

But those calculations were deliberately cautious. A recent survey drew on the expertise of 41 permafrost scientists to offer more informal projections. They estimated that if human fossil-fuel burning remained high and the planet warmed sharply, the gases from permafrost could eventually equal 35 percent of today’s annual human emissions.

The experts also said that if humanity began getting its own emissions under control soon, the greenhouse gases emerging from permafrost could be kept to a much lower level, perhaps equivalent to 10 percent of today’s human emissions.

It sounds like a little thing, but I can't tell you how main mainstream news stories:

1) Avoid using numbers completely.
2) Take the first number they are told and put it in the article, not caring whether the number means anything (here they convert it to a % of human emissions, perfect).
3) Stick to one central number, assuming people will be hopelessly confused by the reality of different estimates.

The author gets to the point of what the numbers mean, too:

Even at the low end, these numbers mean that the long-running international negotiations over greenhouse gases are likely to become more difficult, with less room for countries to continue burning large amounts of fossil fuels. 

The whole article does a great job. Good numbers with appropriate caveats:

Scientists need better inventories of the ancient carbon. The best estimate so far was published in 2009 by a Canadian scientist, Charles Tarnocai, and some colleagues. They calculated that there was about 1.7 trillion tons of carbon in soils of the northern regions, about 88 percent of it locked in permafrost. That is about two and a half times the amount of carbon in the atmosphere. 

Followed by context:

Philippe Ciais, a leading French scientist, wrote at the time that he was “stunned” by the estimate, a large upward revision from previous calculations.
“If, in a warmer world, bacteria decompose organic soil matter faster, releasing carbon dioxide,” Dr. Ciais wrote, “this will set up a positive feedback loop, speeding up global warming.”

 It may be small of me, but I like a little action in my science stories. It reminds us of the absurdity of the denialist portrait of the rent-seeking elitist ivory-tower scientist, running computer simulations from a desk and collecting grant money:

One recent day, in 11-degree weather, Dr. Walter Anthony and an assistant, Amy Strohm, dragged equipment onto two frozen thermokarst lakes near Fairbanks. The fall had been unusually warm and the ice was thin, emitting thunderous cracks — but it held. In spots, methane bubbled so vigorously it had prevented the water from freezing. Dr. Walter Anthony, six months pregnant, bent over one plume to retrieve samples.

“This is thinner ice than we like,” she said. “Don’t tell my mother-in-law! My own mother doesn’t know.”

Well, they know now. And it's for the good of the public; they need to know what scientists really do.

They don't shy away from explaining how unusual these emissions are:

Dr. Walter Anthony had already run chemical tests on the methane from one of the lakes, dating the carbon molecules within the gas to 30,000 years ago. She has found carbon that old emerging at numerous spots around Fairbanks, and carbon as old as 43,000 years emerging from lakes in Siberia.

“These grasses were food for mammoths during the end of the last ice age,” Dr. Walter Anthony said. “It was in the freezer for 30,000 to 40,000 years, and now the freezer door is open.”

And they talk about the danger of fire:

One day in 2007, on the plain in northern Alaska, a lightning strike set the tundra on fire.
Historically, tundra, a landscape of lichens, mosses and delicate plants, was too damp to burn. But the climate in the area is warming and drying, and fires in both the tundra and forest regions of Alaska are increasing.

The Anaktuvuk River fire burned about 400 square miles of tundra, and work on lake sediments showed that no fire of that scale had occurred in the region in at least 5,000 years.

Are they going to leave it there? No, they are going to give you context for the effect of this fire:

Scientists have calculated that the fire and its aftermath sent a huge pulse of carbon into the air — as much as would be emitted in two years by a city the size of Miami.

As well as what the fire means in the broader context of the permafrost:

Scientists say the fire thawed the upper layer of permafrost and set off what they fear will be permanent shifts in the landscape.

Up to now, the Arctic has been absorbing carbon, on balance, and was once expected to keep doing so throughout this century. But recent analyses suggest that the permafrost thaw could turn the Arctic into a net source of carbon, possibly within a decade or two, and those studies did not account for fire.

“I maintain that the fastest way you’re going to lose permafrost and release permafrost carbon to the atmosphere is increasing fire frequency,” said Michelle C. Mack, a University of Florida scientist who is studying the Anaktuvuk fire. “It’s a rapid and catastrophic way you could completely change everything.”

Almost everyone agrees that the legacy media in general and science journalism in particular are on the rocks these days, but Justin Gillis seems not to have gotten the memo. This article is going to win some awards.

Andrew Revkin on methane -- Reassuring, but inaccurate

After the disturbing piece in the Independent, I was looking for somebody to talk me down, and Andrew Revkin seems to have set himself precisely that task in "Methane Time Bomb in Arctic Seas – Apocalypse Not." He is all reassurance:

If you read the Independent of Britain, you’d certainly be thinking the worst. The newspaper has led the charge in fomenting worry over the gas emissions, with portentous, and remarkably similar, stories in 2008 and this week.
If you read geophysical journals and survey scientists tracking past and future methane emissions, you get an entirely different picture:
A paper published in Dec. 6 in the Journal of Geophysical Research appears to confirm pretty convincingly that the gas emissions seen in recent years are from a thawing process that has been under way for 8,000 years — since seas rose sufficiently to cover the near-shore seabed.

I have to say, however, that the more Andy Revkin tries to play the part of the sane middle ground in the climate debate -- not too denialist, not too excited -- the less I am inclined to trust what he says at face value. "I occupy the sane middle ground" is an ideological self-description like any other, and Revkin regularly illustrates the distorting effects that rigidly pursuing that can have. Let's look at the abstract of the paper:

Summer hydrographic data (1920–2009) show a dramatic warming of the bottom water layer over the eastern Siberian shelf coastal zone (<10 m depth), since the mid-1980s, by 2.1°C. We attribute this warming to changes in the Arctic atmosphere. The enhanced summer cyclonicity results in warmer air temperatures and a reduction in ice extent, mainly through thermodynamic melting. This leads to a lengthening of the summer open-water season and to more solar heating of the water column. The permafrost modeling indicates, however, that a significant change in the permafrost depth lags behind the imposed changes in surface temperature, and after 25 years of summer seafloor warming (as observed from 1985 to 2009), the upper boundary of permafrost deepens only by ∼1 m. Thus, the observed increase in temperature does not lead to a destabilization of methane-bearing subsea permafrost or to an increase in methane emission. The CH₄ supersaturation, recently reported from the eastern Siberian shelf, is believed to be the result of the degradation of subsea permafrost that is due to the long-lasting warming initiated by permafrost submergence about 8000 years ago rather than from those triggered by recent Arctic climate changes. A significant degradation of subsea permafrost is expected to be detectable at the beginning of the next millennium. Until that time, the simulated permafrost table shows a deepening down to ∼70 m below the seafloor that is considered to be important for the stability of the subsea permafrost and the permafrost-related gas hydrate stability zone.

Just as important, look at the dates on the paper:

Received 18 April 2011; accepted 28 July 2011; published 19 October 2011.

Sharp readers will note that the dates don't match; the date of publication is Oct 2011, not Dec 2011. We'll get to that in a minute. For the moment let's focus on the paper itself.

Now, I'm not sure this is quite as reassuring vis-a-vis the boiling seas of the East Siberian Arctic Shelf as Revkin seems to think. For although he says "A paper published in Dec. 6 in the Journal of Geophysical Research appears to confirm pretty convincingly that the gas emissions seen in recent years are from a thawing process that has been under way for 8,000 years" this paper was submitted in April, months before scientists were dispatched to the shelf to investigate the expanding methane plumes. So while the study may reassure us about emissions "in recent years" it has nothing to say, specifically, about what the Independent was reporting about -- the very recent trip to examine the area after reports of huge plumes of gas.

Let me be very clear: here at IT, we listen to scientists; we don't dismiss them. Revkin talked to permafrost experts, who feel the recent plumes can be accounted for by their permafrost model. That model also says we don't need to worry about a large amount of methane escaping the East Siberian Arctic Shelf. However, it does not appear that that model was developed with, tested by, or compared to the data from the expedition dispatched in September (remember, the paper was submitted in April!) So unless there is more to the story, the scientists Revkin spoke with may think they can explain the observations, but they haven't explained the observations as yet. Indeed, the observations haven't even been reported yet.

I initially assumed -- I'm sure this wasn't deliberate on Revkin's part -- that when he referred to a paper published Dec 6, which reassures us about the findings of the expedition dispatched in September, that the paper was about the expedition dispatched in September. It is not. It's about a model of permafrost melting. And to be absolutely clear, we do not scorn modelling studies at IT. They are very important. The paper says that the model can adequately explain the small methane plumes observed in prior years as part of a long-term process, not a short-term, rapidly worsening degradation of permafrost. But there is no indication that the model has been tested against the new observations. The timeline doesn't seem to work.

I also thought -- and this time based on what Revkin explicitly stated -- that he had linked to the study published on Dec 6. Here's the quote:

But read this summary of the paper from the American Geophysical Union, which publishes the journal, and see if you feel reassured that the “methane time bomb” there is safe for a long time to come:

[T]he authors found that roughly 1 meter of the subsurface permafrost thawed in the past 25 years, adding to the 25 meters of already thawed soil. Forecasting the expected future permafrost thaw, the authors found that even under the most extreme climatic scenario tested this thawed soil growth will not exceed 10 meters by 2100 or 50 meters by the turn of the next millennium. The authors note that the bulk of the methane stores in the east Siberian shelf are trapped roughly 200 meters below the seafloor… [Read the rest.]

Here’s the link to the paper itself: “Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability.”

But if you click on the link to the AGU summary, you quickly slowly realize that these are two different papers, one called "Siberian shelf methane emissions not tied to modern warming" by Colin Schultz, and “Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability,” by Dmitrenko et al. the AGU summary was published Dec 6; the actual paper was published October 19.

So Revkin has conflated two different papers by different authors into one confused the summary's date of publication with the paper itself; he started off talking about the Independent's account of Dr. Semiletov's recent trip to the Arctic and his recent AGU presentation, but he didn't talk to Semiletov or reference that presentation.

So the Independent did publish a sensational story, a story that does look remarkably similar to one they published in 2008 (a good catch by Revkin.) But if you are comparing the two stories, the Independent's has this claim: they actually wrote about the findings of the expedition. They referred to Semiletov's talk at the AGU, which presumably relates to his paper in press "Trace gas emissions from sub-sea permafrost" (no abstract I could find) and not to either of the papers published by different authors about permafrost models developed prior to the recent observations.

So while it is as a general rule wise not to panic, and, especially on the subject of science, to wait for the dust to settle before reaching any conclusions, all the facts cited by Revkin in support of his languor are reported inaccurately and/or oversold.

Andy Revkin now wears the hat of a blogger, but he sometimes seems to have brought with him into his new career the very attributes that brought about the decline of traditional journalism: he is sloppy, he cares more about appearing moderate and fair than reporting the facts accurately, and while tsk-tsking at the sensationalism of the Independent, he neglects to do the basic stuff like talking to the principal people involved and actually getting the facts about the subject of his article.

Update: Revkin's response is below. I reply here.

5.9%

What happened after 2004? The black line is now at 10,000.

Emissions rose 5.9 percent in 2010, according to an analysis released Sunday by the Global Carbon Project, an international collaboration of scientists tracking the numbers. Scientists with the group said the increase, a half-billion extra tons of carbon pumped into the air, was almost certainly the largest absolute jump in any year since the Industrial Revolution, and the largest percentage increase since 2003.

The growth in CO2 emissions was expected to spike after the recession-induced dip last year. But 5.9%? That's a disaster. We can't afford many more years like 2010, doubly since scientists are warning that melting permafrost will add a hefty chunk of carbon to our own slug of emissions (380 billion tons -- roughly thirty-eight year of emissions at the 2010 rate. Meaning that as we talk about getting serious about reducing emissions, as we argue about the Keystone XL, we have already locked ourselves in for another forty years' worth of rapid climate change.)

Skeptical Science on permafrost melting

SkS has a post up on the decay of permafrost. Catnip to me, of course. It's a good summary, and highlights a number of issues. Here's one I hadn't thought about much:

Commercial activities in the Arctic are large, important to national economies and for the viability of local population centres.  Monitoring of permafrost melting and associated greenhouse gas emissions is undertaken by ground instruments and satellites.  However, unless technology able to replace melting permafrost with an affordable, durable load bearing foundation can be applied, it should be accepted that virtually all existing buildings and structures located on permafrost with foundations less than 5 metres deep are likely to be damaged or destroyed before 2100.

That's the homes and businesses of millions of people; oil, gas, and mining infrastructure, utilities and transport infrastructure, etc. The rapid erosion of the Arctic's 100,000km coastline (which is made of little rocks glued together with the aforementioned permafrost) also gets a good treatment.

They don't precisely estimate the amount of feedback from carbon (methane and carbon dioxide) released by melting permafrost. I don't know the answer either, although I discuss some estimates here and here. If you said 25-100ppm of CO2 in additional carbon by 2200, I don't think anyone could tell you you were wrong. If I find a better estimate, I'll post on it.

Permafrost FAQ

1. Why do we never hear about Antarctic permafrost?

Because for complicated reasons it doesn't store very much carbon (touch wood!) Since there are few people there, no one really cares.

2. I'm sick of reading wildly different estimates of the potency of methane as a greenhouse gas compared to CO2. What's the real number?

A molecule of methane traps heat hundreds of times better than a molecule of CO2. But it decays much faster. The really high estimates you see are molecule-to-molecule comparisons; the lower ones are long-term comparisons. The long-term comparisons turn out to be tricky. Methane is worse than CO2; and when it decays it turn into CO2, so it's really a lose-lose proposition.

3. Does melting permafrost release CO2 or methane?

Either CO2 or both. The methane makes headlines but the research I highlighted here suggests the CO2 is actually the bigger problem. More on methane here.


4. Can we stop the melting of the permafrost?

Probably not, given the feedbacks that have already kicked in, and Arctic amplification which we see rapid warming of the North even with radical emissions reductions. Short of large-scale geoengineering, the permafrost is going to go. The additional warming will further accelerate global warming.

More methane madness

 

From "arctictransport":

Something strange

Posted on September 14, 2011 by rusfedmin

Commercial shipping through the Northeast Passage over the last couple weeks has reported the seas bubbling as if they were boiling.  Their observations have been reported to the science ministry who have sent scientists to investigate.

H/t Steve Bloom.

The image above is from "Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions" (Isaksen et al 2011). Although it sounds specialized, the paper, which is available in full, answers a number of basic beginner's questions about methane release (I needed to look those up . . . for a friend. Or for you, the reader. Yeah, that's it. For you the reader.)

1. How much methane is in the atmosphere now?


"The atmospheric concentrations in 2005 correspond to an atmospheric burden of 4,900 Tg CH4 (1 Tg = 1012 g)."


2. How long does it reside in the atmosphere?


"Atmospheric CH4 has a global average atmospheric lifetime of approximately 8 to 10 years [Denman et al., 2007]."


3. Why so brief, compared to CO2?

"Atmospheric CH4 is removed through oxidation by the hydroxyl radical (OH), mainly in the troposphere: R1    CH4 + OH --> H2O + CH3"


4. What is its ultimate fate?


Mostly to decay to CO2 (and ozone). So the best case scenario when you lose a ton of methane into the atmosphere is that it quickly oxidizes into a ton of CO2. Which, since it hangs around a lot longer and is the stuff that got us into this mess, is not so great.

5. There are only so many the hydroxyl radicals (OH) in the atmosphere. What happens if you release a bunch of it all at once?

It hangs around longer -- much longer -- leading to the amplified warming effect that gives the paper its title.

6. How much methane is in methyl hydrate deposits, compared to the atmosphere?

"The most recent review of the numerous published estimates of the amount of methane sequestered in global gas hydrate deposits converges on a range of 3 to 40 × 1015 m3 of methane [Boswell and Collett, 2011], which converts to a range of ∼1,600 to 21,000 Pg C."

1Pg = 1,000 Tg. So the amount of methane in the deposits is estimated to be between 300 times as much and 42,000 times as much as the total amount of methane in the atmosphere today.

7. Fuck me.

If any significant fraction of it escaped into the atmosphere on a human timescale, yes, that would be the general idea.

8. Could that happen? Really?

"Shakhova et al. [2008] speculate that 50 Pg CH4 could be released abruptly at any time from gas hydrates associated with subsea permafrost. Although there is no basis for estimating the rate of such a release, this value is used as a worst case scenario for the numerical model studies."

 9. Do they think such a release is likely?


No. "Although the high‐emission scenarios are unlikely to occur, they are compatible with the current knowledge of the cumulative magnitude of CH4 that might be emitted from permafrost thawing and from CH4 hydrate destabilization."

10. But worse case?

It's hard to call this the worst case, since what they are postulating is the release of less than 1% of the total reserves. But for the estimate they chose as a plausible worst case, 50 Pg, the short-term effect would be a global increase in radiative forcing of about 4W/m^2 (although, confusingly, they say 50 Pg could be released in one year, and then they model it as released over thirty years, significantly blunting the effect.)

The effect would be similar to doubling CO2 concentrations overnight. Temperatures would immediately rise, probably by 1-2C, with further rises in the following decades, depending on just what the actual climate sensitivity turns out to be.


Final thoughts from Iksaksen:

Fossil fuel CO2 emissions have increased substantially over the last decade and is now 40% higher than in 1990 [Le Quéré et al., 2009; Myhre et al., 2009]. The continued increase in greenhouse gas emissions toward the end of this century has the potential to produce significant warming at high northern latitudes well beyond what has been observed during the last decades [Hansen et al., 2007; IPCC, 2007]. There is a possibility that the Arctic temperature increases could be followed by extensive permafrost thawing, with enhanced CH4 emission from thermokarst lakes [Walter et al., 2006], with later release of CH4 from gas hydrates that would eventually be affected by warming temperatures. Considering the large, nonlinear atmospheric chemistry feedbacks discussed here, future CH4 emissions from permafrost deposits could be a larger concern for climate warming than previously thought.

 

Permafrost and climate change: a primer

This great 2008 article runs through the basics of what we know.

Point the first: there's a lot of carbon there.

Still, 1672 Pg could be an underestimate of total soil C pools in the permafrost region, because deep soils were only considered for one area in northeastern Siberia and for river deltas, and because the soil C content in the 2- to 3-m layer of most mineral soil orders was conservatively estimated because of data scarcity. Both the 2- to 3-m layer and the deep soil C estimates should be considered preliminary because a relatively small number of data points are extrapolated to large areas, but this provides a general outline to the size of this deep C pool. Overall, this permafrost C pool estimate is more than twice the size of the entire atmospheric C pool, and it is more than double previous estimates of high-latitude soil C (Gorham 1991, Jobbágy and Jackson 2000). The 0–3 m permafrost-zone soil C estimated here at 1024 Pg represents a large fraction of world soil C stocks; global soil C stocks from 0 to 3 m depth (peatlands not included) have been estimated to be 2300 Pg (Jobbágy and Jackson 2000).

While the general picture is clear -- permafrost warms, and some of the carbon stored therein makes its way into the atmosphere -- there are a bewildering array of factors that affect how much and what kind of carbon is released in warming conditions by a particular piece of permafrost.

The freezing point of water is a change of physical state that causes orders-of-magnitude threshold changes in biotic processes, including decomposition rates (Monson et al. 2006). It is important to recognize, however, that microbial decomposition of organic C occurs below 0°C in films of liquid water (Price and Sowers 2004). Subzero increases in permafrost temperature can, in theory, have impacts on C losses to the atmosphere, albeit at lower levels. The phase change from water to ice also controls thresholds in abiotic processes. Although permafrost thawing can occur gradually as the thickness of the active layer increases, it can also occur more abruptly through development of thermokarst (ground surface subsidence caused by thaw of ice-rich permafrost) and erosion. The extent and rate of these processes depend highly on initial ground-ice content and other landscape attributes (Osterkamp et al. 2000). They have major impacts on whole- ecosystem C cycling and on the fate of thawed permafrost C because erosion and river transport are significant C loss pathways at regional scales (Berhe et al. 2007).

The particular composition of the permafrost -- the mineral content of the soil, the proportion of water, the local biota -- strongly affect the scale and nature of the emissions. Relative emission rates are calculated for bogs, acidic fens, intermediate fens, cedar swamps, tamarack swamps, and meadows (I was happy to see that meadows proved to be the least GHG-producing terrain type. I've always liked meadows, and I wouldn't want to have to change my opinions. The worst, by far, are the bogs, but who likes bogs to begin with?)



The article discussion four separate mechanisms of permafrost thawing that vary in importance at different stages of warming:

Four different mechanisms that can thaw permafrost. Each panel represents a hypothesis of the relative importance of that mechanism through time as permafrost thawing progresses. (a) Active layer thickening is the most important mechanism early in permafrost thawing as air warming affects the surface permafrost, but then decreases in importance as taliks begin to form. (b) Talik formation occurs only when active-layer thickening has become deep enough so that the entire summer-thawed layer does not refreeze in the winter. Once this has occurred, by definition, deeper permafrost thawing occurs through talik expansion, and thus active-layer thickening does not contribute directly to permafrost thawing at that time. (c) River and coastal erosion increases through time, but after some maximum effect, this mechanism decreases to zero because the influence of the river and coastal processes is limited in spatial extent. (d) Thermokarst development is represented as a threshold process; the first peak is conceptualized as the loss of Little Ice Age ice. Thermokarst subsequently declines in importance until enough thawing has occurred to affect Pleistocene-age ice, typically somewhat deeper in the soil profile, causing the second peak in thermokarst development. This time course is conceptualized as the course of a single latitudinal band through time; if multiple latitudes are considered simultaneously, then more southerly and northerly regions would be on different points on the axis of permafrost thaw at the same time. The actual number of years these time courses take is not yet known and depends on the progression of climate change, but the range is on the order of multiple decades to centuries. Lastly, the importance of the different mechanisms relative to one another is poorly known. It is clear that river and coastal erosion are the most spatially limited. Here, active-layer thickening and talik formation together are shown as roughly equal, or somewhat greater, in importance to thermokarst formation, which is more restricted to areas with higher ice content.

Carbon leaving the permafrost may leave as CO2, as the more potent greenhouse gas methane, or be captured by vegetation or groundwater flows before it reaches the atmosphere. Methane is liberated (sometimes) by anaerobic reactions, while the product of aerobic reactions is CO2. This might seem to make anaerobic (low oxygen) decomposition the major villain, but the authors believe that it is actually aerobic environments which constitute the greater threat over human timescales, because the decomposition, even though it produces little methane, is so much faster:

Decreased microbial decomposition rates attributable to oxygen limitation in aquatic environments are, therefore, offset in part by the greater length of time spent in a thawed state, and by release of CH4 in addition to CO2. Based on (a) net C emissions from long-term laboratory anaerobic and aerobic incubations of various wetland soils (Bridgham et al. 1998) and (b) the global warming potential of CO2 and CH4 (IPCC 2007), a simple calculation suggests that aerobic decomposition has a greater feedback to warming on a century timescale, ranging from 1.3 to 6.9 times greater than the effect from the same soil decomposed in an anaerobic environment (table 1). This is largely due to differences in C emission rates: aerobic CO2 release is about an order of magnitude higher than anaerobic CO2 release, and about two orders of magnitude more C loss than anaerobic CH4 release (table 1).

Confused? Try this helpful diagram:



Did that help? It didn't help me much. Better press on.

So imagine this pool of carbon, unfrozen and exposed to the world, but not immediately injected into the atmosphere. Microbes are doing what all nonphotosynthetic life does, taking up carbon and oxidizing it to derive energy. Respiration, in other words. This doesn't suck up all the carbon and burn it overnight. Unfortunately, there is a process rather famous for burning through fuel.

In addition to biological decomposition, disturbance by fire could be an important abiotic mechanism for transferring C thawed from permafrost to the atmosphere. Fire oxidizes organic C primarily to CO2, but also releases smaller quan- tities of CH4, carbon monoxide, and other volatile C com- pounds. Because organic C emerging from permafrost is typically located deeper in the soil profile when the active layer thickens, it is less vulnerable than surface organic C to burn- ing. However, extremely warm years, when large amounts of permafrost C thaw, are also more likely to have more extensive or severe fires than average. Model scenarios of fire in Siberia show that extreme fire years can result in approximately 40% greater C emissions because of increased soil organic C consumption (Soja et al. 2004). In combination with dry conditions or increased water infiltration, thawing and fires could, given the right set of circumstances, act together to expose and transfer permafrost C to the atmosphere very rapidly. Lastly, fire can interact with decomposition by creating warmer soil conditions and deeper permafrost thaw, which in turn promote the loss of C from increased microbial activity.

My take-home from this is, first, if you want to second-guess scientific conclusions in this area, better settle in for some long days at the library. This stuff is not simple. Second, we have a load of carbon coming our way, exactly how much and how fast to be determined (one estimate here) -- and after going over this article in detail, I have a better sense for why it's a hard number to estimate. Finally, the Brothers Grimm and Disney have it right: meadows are good; bogs are bad.

More carbon and more problems

Methane continues to climb:



One model puts a number on the estimated CO2 release from permafrost. It's a big one:

One- to two-thirds of Earth’s permafrost will disappear by 2200, unleashing vast quantities of carbon into the atmosphere, says a study by researchers at the Cooperative Institute for Research in Environmental Sciences (CIRES) National Snow and Ice Data Center (NSIDC).

“The amount of carbon released is equivalent to half the amount of carbon that has been released into the atmosphere since the dawn of the industrial age,” said NSIDC scientist Kevin Schaefer. “That is a lot of carbon.”

That's an understatement. We're talking about the same amount of carbon released over the past fifty years. The total increase measured in the modern instrumental record.

Permafrost melting is not modeled in the IPCC's assessments. It was believed for many years to be too slow a feedback to matter on a human timescale. Would it were so. But maybe it's an over-estimate? Those wacky climate scientists, always chasing the headline? What about it, guys?

This estimate may be low because it does not account for amplified surface warming due to the PCF itself and excludes some discontinuous permafrost regions where SiBCASA did not simulate permafrost.