Conservative Scientists & its Consequences

[jai mitchell]

This is why Mike's assertions are misplaced.

The uncertainty in CO2 projections is mainly attributable to uncertainties in the response of the land carbon cycle. As a result of simulated higher CO2 concentrations than in the concentration-driven simulations

Indeed, when one looks at the C4MIP carbon cycle feedback runs, there is actually as much variance in global emissions scenarios as there is variance between RCP 2.6 and RCP 8.5 prescribed scenarios.

The simple fact is this:  in the model runs used to generate the ESM response, only 7 out of 11 runs produced an INCREASE in emissions.

I would also bet good money that their models did not include the effects of a significantly more rapid arctic amplification as a result of summer sea ice loss. (indeed, they are looking only at carbon cycle feedbacks, not frozen soils!)  In this they are probably modeling only the steric gradual changes in arctic warming that come vis-à-vis GHG radiative forcing values and are not including the recent analyses of Atmospheric Impacts to Sea Ice Decline.  I also extremely doubt that they are including albedo feedback responses accurately, since Caldeira and Cvijanovic only recent showed that the ice free state is equal to a CO2 doubling  effect of radiative forcing.  As well as the atmospheric impacts as noted above:  (paper here) http://link.springer.com/article/10.1007%2Fs00382-015-2489-1

Finally, this paper is deficient because it only looks at the carbon cycle feedback effects (not frozen soils!) under the RCP 8.5 scenario.  They back-load the carbon cycle feedback emissions toward the latter half of the century through faulty models (arctic amplification AMOC slowdown), they including excessive carbon capture values of both land and sea (consider the modeled reduction of the AMOC on overturning ocean CO2 capture = a 15% reduction in total global CO2 natural sequestration) AND by looking only under the RCP 8.5 scenario, the human sourced emissions have already worked well toward saturation so the incremental increase in concentration, though severely understated, has a lower incremental effect. 

--

P.S. a globally averaged warming of 3.7 or 3.9 is completely incompatible with the continuity of human civilization.  You are acting like these results of the paper are somehow comforting, I find that extremely distasteful.

[AbruptSLR]

The linked reference show that the US NRC is seriously considering the use of geoengineering.  Research has shown that when denialist are given the option of implementing geoengineering they are then more willing to accept climate change science because it allows them to maintain a large ego (free to do with Earth Systems what they will) and a puffed-up sense of control.  However, as the following extract indicate any reasonable person would realize that the implementation of geoengineering is an act of desperation as if for no other reason it could amount to a declaration of war on the nations that the geoengineering hurts.  If society cannot even pay for better controls on emissions isn't it a fool's dream to believe that it is better to pay large sums of money in the near future that will create even further problems?

NRC, (2015), "Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration"

http://www.nap.edu/catalog/18805/climate-intervention-carbon-dioxide-removal-and-reliable-sequestration

See also:

http://www.latimes.com/nation/la-na-climate-technology-20150210-story.html

Extract: "The lack of progress for more than two decades, however, makes it “increasingly likely that as a society we will need to deploy” some forms of the least-risky technologies to reduce the Earth's temperature, they said.
…

The scientists acknowledge that developing risky tools to counteract global warming carries a "moral hazard," in which nations may become even less motivated than they are now to take immediate steps to combat climate change. But not having the tools in hand might also result in future actions without adequate scientific research.

“People are going to read these reports and they are going to be very scared about the future,” McNutt said.
…

"That scientists are even considering technological interventions should be a wake-up call that we need to do more now to reduce emissions, which is the most effective, least risky way to combat climate change," McNutt, a former director of the U.S. Geological Survey, said in a statement. "The longer we wait, the more likely it will become that we will need to deploy some forms of carbon dioxide removal to avoid the worst impacts of climate change.""

See also:

http://news.sciencemag.org/climate/2015/02/u-s-should-fund-climate-engineering-research-report-concludes

[Lennart van der Linde]

I believe that the IPCC is accurate in their conclusions.

I believe they are imperfect and will be a mix of overestimates and underestimates.

I believe that considering only the middle case underestimates potential risks - the small chance of very large impacts at the high end of IPCC estimates outweigh the small chance of milder impacts at the low end.  Very roughly - 10% chance of low impacts cost = 1, 80% chance of moderate impacts cost = 10, 10% chance of high impacts, cost = 100.  Expected cost = 10%*100+80%*10+10%*1 = 18.1, which is much higher than the expected cost of the middle impact.

I believe that any claim that the high range estimates have more scientific support for being likely than the mid range impacts is ignorant.

So with these four beliefs, what is in your view an appropriate mitigation target and carbon budget?

Hansen et al 2013 (PlosOne) argue we've only 130 GtC left to burn and think that could keep warming below 1.2 degrees C, while Bill McKibben thinks this would give an 80% chance of keeping warming below 2 degrees C (under some different assumptions):
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081648

To what extent do you or don't you agree with Hansen et al, and why?

Michael, since you agree IPCC gives carbon budgets for different climate mitigation targets and probabilities, what would your preferred target be? Something in the line of Hansen et al, which is what Bill McKibben and 350.org are campaigning for (including myself), or something else, and why?

[AbruptSLR]

While Michael decides how to respond to Lennart's question in Reply #602, I provide the following rather lengthy extract, from the linked article, as background (which in my opinion is somewhat conservative) on this question:

http://www.carbonbrief.org/blog/2013/10/carbon-briefing-making-sense-of-the-ipcc%E2%80%99s-new-carbon-budget/
Extract: "The latest report is the first to include an assessment of a "carbon budget" - a finite amount of carbon that can be burnt before it becomes unlikely we can avoid more than two degrees of global warming.
So how big is the carbon budget, how was it calculated, and how does it help us understand the challenge of limiting climate change?

A budget for two degrees
In 1992, the United Nations Framework Convention on Climate Change (UNFCCC) decided the objective of global climate policy should be to stabilise humans' influence with the climate below the level at which it can be considered "dangerous".
The most widely accepted threshold is two degrees of warming relative to pre-industrial times - this is the limit recommended by the UK's Committee on Climate Change, for example.
In its new report, the IPCC includes a calculation of how much carbon we can emit and still have a reasonable chance of staying below two degrees.
It calls this amount a carbon budget. The budget is an upper limit on total human emissions, from the beginning of the industrial revolution until the day we stop burning carbon.
To stick to the budget, any fossil fuels that would take us over-budget will either have to be left in the ground, or the emissions captured before or after entering the atmosphere.

1000 billion tonnes
So how big is the budget? For it to remain likely that we stay below two degrees, the total amount of carbon released through carbon dioxide emissions must be less than 1000 billion tonnes, the IPCC says. 'Likely' here means a 66 per cent chance.
It's possible to calculate a budget like this because carbon dioxide, which is the biggest contributor to global warming, has a predictable relationship with temperature. The warming we get is almost directly proportional to the total amount of carbon dioxide that accumulates in the atmosphere.
The budget is calculated using a measure of how sensitive the planet is to carbon dioxide called the transient climate response to carbon emissions ( TCRE). This is defined as the change in average global surface temperature for a given amount of carbon dioxide accumulated in the atmosphere.
The calculation takes into account processes that amplify or reduce the warming we see in the atmosphere, which are known collectively as feedbacks. These are complicated, introducing uncertainties to the calculation. Because of this, the carbon budget is expressed as the probability of staying below a certain temperature, rather than a guarantee that's what will happen.

How much of the budget has been used up by carbon dioxide?
The IPCC report says that between the start of the industrial revolution and 2011, carbon dioxide emissions from human activity added about 531 billion tonnes worth of carbon to the atmosphere.
Uncertainty around that figure means it could be anywhere between 446 and 616 billion tonnes but broadly-speaking, this would mean that about half the carbon budget is already spent.
Including other gases shrinks the budget
While carbon dioxide is the main greenhouse gas resulting from human activity, it's not the only thing causing the atmosphere to warm. Methane, CFCs, ozone, nitrous oxide and soot all have an overall warming effect.
To stick within the two degree target, this means the budget for carbon dioxide emissions ends up being less than the original 1000 billion tonnes.
In the draft Summary for Policymakers given to governments to review back in June, the IPCC scientists stopped short of including a concrete figure for how much these other gases tighten the budget for carbon dioxide emissions.
That was because their warming effect is less straightforward than for carbon dioxide. But after calls from governments for something more tangible to work with, the final version of the Summary for Policymakers included scientists' best estimate of what the reduced budget would be.

800 billion tonnes
The Summary for Policymakers states that taking into account additional warming factors, the amount of carbon that can be released through carbon dioxide emissions - in total - comes down to about 800 billion tonnes.
That figure comes from scientists' estimate of the total warming expected from the non-carbon dioxide factors, which comes to about 0.4 degrees Celsius by the end of this century.
Given the target of staying below two degrees of warming overall, that leaves 1.6 degrees of warming to come from carbon dioxide. Using the relationship between carbon dioxide and temperature, staying within that budget means carbon dioxide emissions over the industrial era cannot contribute more than 800 billion tonnes of carbon.
The numbers here relate to the IPCC's lowest emissions scenario, RCP2.6, which was specifically designed to show how warming can be limited to two degrees. This means the IPCC have made assumptions about the non-carbon dioxide factors, which could be higher or lower in scenarios with weaker or more stringent mitigation of non-carbon dioxide factors. The upcoming report of the IPCC's Working Group 3 will look at this in more detail.

How far, how fast?
With a budget for carbon dioxide emissions of 800 billion tonnes worth of carbon, and assuming that we had already put 531 billion tonnes into the atmosphere by 2011, it's more accurate to say we've spent two thirds of the budget, not half.
And with about 270 billion tonnes of carbon left in the budget, and current carbon dioxide emissions contributing around 10 billion tonnes per year, the budget is set to be exhausted in about 25 years.
If there are other sources of warming that aren't accounted for in climate models, the budget could be smaller still. For example, models don't currently include permafrost methane emissions - as there's too much uncertainty about them. Including these in the budget could shrink it further.

Adjusting the budget
If we want a better chance of staying below two degrees, a smaller carbon budget improves the odds.
On the other hand, Governments also asked the IPCC to calculate what running a bigger risk of surpassing two degrees would do to the budget. The Summary for Policymakers says expanding the budget to 840 billion tonnes of carbon would give a 50:50 chance. Upping it to 880 billion tonnes reduces the chance to a third.
Rather startlingly, that means that with current emission rates of 10 billion tonnes per year, the difference between a carbon budget of 800 and 880 billion tonnes is just eight years worth of current emissions. That bigger budget halves the chance of staying below two degrees, the IPCC says, from 66 per cent to 33 per cent.
Last month's calls for greater clarity over the IPCC's new budget calculations could be taken as a sign that governments are looking for clearer signs on how far emissions cuts need to go and how quickly. But it remains to be seen the level of risk they're willing to accept, or how a worldwide cap on emissions might be divvied up between nations.
Something to consider, as the 2015 deadline for reaching an international climate agreement approaches.

A note on units: Because carbon dioxide is the main contributor to warming, the budget is sometimes expressed in terms of tonnes of carbon dioxide rather than carbon. Carbon dioxide has a higher mass than carbon, so the budget for carbon dioxide emissions can be expressed either as 800 billion tonnes of carbon, or 2936 billion tonnes of carbon dioxide - but it's essentially the same thing."

[Lennart van der Linde]

Claiming climate science is a giant conspiracy covering up the true horror is as lame as claiming it is exaggerating it...

We are asking people to take a huge change in their lives, a huge change in the economic foundation of their society. We have to do that on the most sound science we have, not on the most interesting or exciting.

This is not a game. When we go to people and say their energy bills have to rise or we have to use less energy we cannot do so just because a bunch of partisan members of the climate debate are on board we have to be convinced the uncommitted that all of science is convinced.

This is a sober and sombre undertaking done with reluctance acknowledgement of the risks. We are telling people to make huge changes to their lives. We do so with heavy hearts and with full knowledge what we say is built on strong science that has withstood the critiques of dissent not just the most exciting that fulfils your personal desires.

Where has it been claimed here that climate science is a giant conspiracy covering up the true horror?

And yes, based on the most sound science we have, fully recognizing the uncertainties, many here are asking for a huge change in the economic foundation of our society, namely to actually base this foundation on sound science and not on an ideology of unlimited growth on a limited planet. You may call this asking people to make huge changes in their lives, but the alternative is potentially forcing future generations to hardly have a life at all. What seems the moral and responsible thing to do?

Consider what Jim Hansen wrote in 2007 on scientific reticence and sea level rise:
http://iopscience.iop.org/1748-9326/2/2/024002/fulltext/

Abstract:
"I suggest that a `scientific reticence' is inhibiting the communication of a threat of a potentially large sea level rise. Delay is dangerous because of system inertias that could create a situation with future sea level changes out of our control. I argue for calling together a panel of scientific leaders to hear evidence and issue a prompt plain-written report on current understanding of the sea level change issue."

Has this report been written yet? Or was Hansen being alarmist, as some claim?

Science since 2007 seems to slowly move into agreement with this view of Hansen, as this and other threads, mainly in the Antarctic folder show. But still it is at risk of erring on the side of least drama. Is that risk less dramatic than asking people now to make (relatively small) changes to their lives that may help future generations to also have a good life instead of potentially hardly a life at all?

[Michael Hauber]

"In general the strongest effect of a feedback will be immediate..."

I don't know about generally, though a linky would be nice if that is an overall tendency.

The point is, though, that we are not talking about 'generally.'

We are talking about specific carbon feedbacks.

Archer and others don't think, for example, that subsea methane and other carbon feedbacks will behave in the way you describe.

We can only pray that they are the ones who are right, and not the ones doing most of the on-the-ground research in the area.

It doesn't seem likely that terrestrial permafrost will act that way, either.

...

The permafrost at the surface is the easiest to melt.  After that is melted there is then an increasing depth of insulation from soil above to slow down the melt.  Therefore permafrost melt should be the fastest right at the start. 

This is very simple for an instantaneous forcing (e.g. model experiments where Co2 is instantly doubled and then the model run to see what happens). 

A complicating issue is when temperatures change over time.  The feedback response to any specific level of forcing will still follow the above behaviour.  However over time you could get an effect where both the amount of area being melted goes up so that the feedback level increases over time, until the amount of area that totally melts out can balance out the new areas melting as the melt zone moves further north.

[sidd]

"The permafrost at the surface is the easiest to melt.  After that is melted there is then an increasing depth of insulation from soil above to slow down the melt.  Therefore permafrost melt should be the fastest right at the start. "

Unless. of course, heat is advected by percolating water, just as in the icesheets, where the timescale estimate went from glacially diffusive to the heart-stoppingly brisk rates seen in cryo-hdrologic warming ...

sidd

[Michael Hauber]

In another thread ASLR posted this very good popular article by Kerry Emanuel on fat tail risks and alarmism:
http://climatechangenationalforum.org/tail-risk-vs-alarmism/

Very much to the point here as well.

Fat tail risk is very important and a point I agree with.  It is a different point to claiming that scientists or the IPCC are being conservative and underestimating the middle range.  Warming is as likely to be at the low end as the high end.  However as I've stated before the risks of the high end outweigh the benefits of the low end and so our response to the climate change should not be focused on the middle range, but on the upper range, similar to when we buy insurance.  We don't pay insurance because of the expected most likely case, but because of the low risk of an extreme result. 

In the same way I don't want to act on climate change because of the most likely case, but because of the low risk of an extreme case.  My preferred target for Carbon is 0, as every extra tonne of carbon increases this low risk of an extreme case and I don't believe there is any such thing as a safe carbon budget.  Rather any carbon budget is a political compromise which should consider the human nature reality that setting a target can often result in a stronger effort to meet that target then setting a general target of 'as low as possible'.  Our carbon target should not be based on climate science, but a political assessment of what is tough but possible.  Research into performance management shows this is the best approach to getting the best possible outcome.

[Michael Hauber]

This is why Mike's assertions are misplaced.

The uncertainty in CO2 projections is mainly attributable to uncertainties in the response of the land carbon cycle. As a result of simulated higher CO2 concentrations than in the concentration-driven simulations

Indeed, when one looks at the C4MIP carbon cycle feedback runs, there is actually as much variance in global emissions scenarios as there is variance between RCP 2.6 and RCP 8.5 prescribed scenarios.

The simple fact is this:  in the model runs used to generate the ESM response, only 7 out of 11 runs produced an INCREASE in emissions.

I have no idea what this is supposed to mean.

I would also bet good money that their models did not include the effects of a significantly more rapid arctic amplification as a result of summer sea ice loss. (indeed, they are looking only at carbon cycle feedbacks, not frozen soils!)  In this they are probably modeling only the steric gradual changes in arctic warming that come vis-à-vis GHG radiative forcing values and are not including the recent analyses of Atmospheric Impacts to Sea Ice Decline.  I also extremely doubt that they are including albedo feedback responses accurately, since Caldeira and Cvijanovic only recent showed that the ice free state is equal to a CO2 doubling  effect of radiative forcing.  As well as the atmospheric impacts as noted above:  (paper here) http://link.springer.com/article/10.1007%2Fs00382-015-2489-1

As I previously noted current Arctic sea ice loss is very reasonably close to what is predicted in CMIP5 models.  It was the previous models which seriously underestimated Arctic sea ice loss.  There is also the Antarctic sea ice which is gaining more ice, and I'm reasonably confident that overall CMIP5 models are overestimating global sea ice loss.  However they are also significantly underestimating NH snow cover loss in summer and I'd expect this is by enough to outweigh the slower than modelled loss of global sea ice.

Finally, this paper is deficient because it only looks at the carbon cycle feedback effects (not frozen soils!) under the RCP 8.5 scenario.  They back-load the carbon cycle feedback emissions toward the latter half of the century through faulty models (arctic amplification AMOC slowdown), they including excessive carbon capture values of both land and sea (consider the modeled reduction of the AMOC on overturning ocean CO2 capture = a 15% reduction in total global CO2 natural sequestration) AND by looking only under the RCP 8.5 scenario, the human sourced emissions have already worked well toward saturation so the incremental increase in concentration, though severely understated, has a lower incremental effect. 

CMIP5 ESM models include frozen soil effects.  As I linked to earlier NIPCC have a big critique on how the frozen soil effects are not accurate.
--

P.S. a globally averaged warming of 3.7 or 3.9 is completely incompatible with the continuity of human civilization.  You are acting like these results of the paper are somehow comforting, I find that extremely distasteful.

Yes 4 degrees is alarming.  So why invent reasons to expect more warming?

[Michael Hauber]

"The permafrost at the surface is the easiest to melt.  After that is melted there is then an increasing depth of insulation from soil above to slow down the melt.  Therefore permafrost melt should be the fastest right at the start. "

Unless. of course, heat is advected by percolating water, just as in the icesheets, where the timescale estimate went from glacially diffusive to the heart-stoppingly brisk rates seen in cryo-hdrologic warming ...

sidd

The heat for the percolating water still has to come from the surface? (I assume you are talking surface meltwater and/or rain and not a subterranean source).  So percolating water may dramatically reduce the insulating effect of soil above, but it won't eliminate 100% of this effect, and it can't add new heat to the system, so melt will still slow down as it progresses deeper.

[AbruptSLR]

We should all remember that as pointed-out in the linked reference, AR5 lowered its estimate of the TCRE value from its AR4 value; however, work by at least Drew Shindell (2014) showed that this reduction was inappropriate.  Furthermore, emissions are currently rising by 1.8 to 1.9 per cent per year (see the attached image and associated caption about the implications of delaying the reduction in emissions).

Furthermore, we should all remember that the AR5 carbon budget recommendations were based on TCRE values that are likely to be too low (which is non-conservative from a public safety point of view):

Myles R. Allen & Thomas F. Stocker, (2014), "Impact of delay in reducing carbon dioxide emissions", Nature Climate Change, Volume: 4, Pages: 23–26, doi:10.1038/nclimate2077

http://www.nature.com/nclimate/journal/v4/n1/full/nclimate2077.html

Abstract: "Recent downward revisions in the climate response to rising CO2 levels, and opportunities for reducing non-CO2 climate warming, have both been cited as evidence that the case for reducing CO2 emissions is less urgent than previously thought. Evaluating the impact of delay is complicated by the fact that CO2 emissions accumulate over time, so what happens after they peak is as relevant for long-term warming as the size and timing of the peak itself. Previous discussions have focused on how the rate of reduction required to meet any given temperature target rises asymptotically the later the emissions peak. Here we focus on a complementary question: how fast is peak CO2-induced warming increasing while mitigation is delayed, assuming no increase in rates of reduction after the emissions peak? We show that this peak-committed warming is increasing at the same rate as cumulative CO2 emissions, about 2% per year, much faster than observed warming, independent of the climate response."

Also see:

http://www.carbonbrief.org/blog/2013/11/no-time-for-delay-in-cutting-greenhouse-gas-emissions,-say-ipcc-scientists/

Extract: "In its latest report, the IPCC lowered its estimate of TCRE by about 25 per cent compared to the previous report released in 2007."


Caption: "Limiting peak warming to two degrees above pre-industrial means reducing carbon dioxide emissions by 2.4 per cent per year from 2015 (green). Delaying cutting emissions until 2025 means the same rate of cuts results in 2.5 degrees warming (yellow). Staying below two degrees would require much faster emissions cuts. Source: Stocker & Allen ( 2013)."

[wili]

Everyone should read ASLR's links above on plans to geoengineer the atmosphere.

This is really scary sh!t.

Here's the coverage of the story at phs.org:

http://phys.org/news/2015-02-purposely-cooling-planet-idea.html

Panel chairwoman Marcia McNutt, editor of the journal Science and former director of the U.S. Geological Survey, said in an interview that the public should read this report "and say,

 'This is downright scary.'

And they should say,

'If this is our Hail Mary, what a scary, scary place we are in.'"

(I won't pester MH further on feedbacks, but just to point out, does anyone really think that, just because it is near the surface, the top layer of permafrost will all melt rather rapidly??!! Right now the area of net melting is mostly in the southern border of the permafrost area, and is going to spread more or less slowly northward from there. The primary trajectory of melt right now is south to north, which will take some time. And it's not as if after the top layer has thawed that it will the next layer down won't be ready for even more rapid thaw. )

[sidd]

"The heat for the percolating water still has to come from the surface?"

That surface can be very far away, where the rain evaporated in the first place.

[AbruptSLR]

(I won't pester MH further on feedbacks, but just to point out, does anyone really think that, just because it is near the surface, the top layer of permafrost will all melt rather rapidly??!! Right now the area of net melting is mostly in the southern border of the permafrost area, and is going to spread more or less slowly northward from there. The primary trajectory of melt right now is south to north, which will take some time. And it's not as if after the top layer has thawed that it will the next layer down won't be ready for even more rapid thaw. )

wili,
The most direct answer to your question is provided by the long extract from the following linked article, indicating that the Arctic permafrost is more subject to degradation that many scientists previously thought, because the permafrost is not continuous.  Obviously, the cited "unfrozen saline zones" within the permafrost has big implications for example with regard to: (a) the penetration of warm surface water that sidd discusses; (b) accelerated activation of microbes in the soil; (c) accelerated growth of shrubs; and (d) accelerated invasion by insects and burrowing animals like ground squirrels:

http://innovations.coe.berkeley.edu/vol7-issue8-feb2014/studying-the-arctic-tundra.html

Extract:
"The Arctic is critical to understanding the global climate. About half the carbon stored in the Earth’s soil is in the Arctic, where organic matter is locked in place by permanently frozen subsoil. As those regions thaw, the worry is that tiny microbes will start feeding on the long-stored organic material and start releasing large quantities of greenhouse gases.
“Our goal is to understand the structure beneath the subsurface,” says Hubbard. “How thick is the active layer? How thick is the permafrost? What are the variations in moisture content and geochemistry, and how do those variations influence greenhouse gas generation?”
Hubbard’s team is using geophysical tools—seismic, radar and electrical—to determine what’s beneath the ground. They also collect core samples that are analyzed back in Berkeley.
In seismic tests, researchers hit the tundra with a sledgehammer to send an acoustic pulse into the ground. The velocity of the pulse is sensitive to physical structure and reveals whether or not the deeper permafrost layers are frozen.
Last year, these seismic tests led to surprising results. Scientists thought the permafrost started about a half-meter below the ground surface and continued for hundreds of meters. But Hubbard’s team discovered unfrozen saline zones, starting about two meters below the top of the permafrost and running many meters deep.
“We chose the Barrow site because it is cold and had continuously frozen permafrost,” says Hubbard, laughing. “And we find out that the northernmost city in North America, with supposedly the most continuous permafrost area, is not really continuous. It could have big implications. There could be microbes right now that are active in this buried, unfrozen zone, with wintertime or even yearlong greenhouse respiration. We will be returning to the site this May to drill deep holes, collect gas samples and test this hypothesis.”
Hubbard’s team is also measuring the subsurface with ground penetrating radar, which sends electromagnetic waves into the ground that bounce off the interface between sublayers. The measurements are taken by pulling radar-equipped sleds across the Arctic tundra, either on foot or behind a snowmobile.
“We’ve found radar to be extremely helpful for mapping the active layer,” says Hubbard. “We’ve been going up there every freeze, winter, thaw and growing season for a few years and measuring the active layer dynamics—basically, the thaw depth.”
They also measure the moisture content, based on the subsurface’s ability to conduct electrical current. This electrical data is taken either by planting electrodes in the ground or pulling an electromagnetic sensor across the tundra.
All of these subsurface measurements of the Barrow Peninsula are critical to understanding how the Arctic is changing. But NGEE-Arctic also seeks to understand the relationship between the changes below ground to the land above.
“We’ve been taking kites mounted with sensors to image the land surface at the same time that we’re imaging the subsurface,” says Hubbard. In the past, they’ve also used landscape data mapped from a twin engine Cessna plane.
The goal is to transfer the knowledge of their detailed subsurface measurements to the scale used in standard climate models. Hubbard’s team measures subsurface features in centimeters, but the smallest element in a climate model is 30x30 kilometers—a million times larger.
“There is a tight coupling of the land surface and the below-ground expression,” says Hubbard. “We would like to be able to infer a lot about the subsurface from measuring the micro-topography. That would really help us to parameterize this big climate model, because it is easy to acquire topographic measurements.”
NGEE-Arctic is an ambitious, 10-year study that’s funded by the Department of Energy. Despite the harsh conditions of the fieldwork, scientists are very excited about the project."

While this is the most direct answer to your question I will try to provide a couple more posts indicating the large number of factors that need to be considered to more fully address your question; which in-truth would require a state-of-the-art ESM like ACME to answer appropriately.

Best,
ASLR

[wili]

Thanks, again, ASLR. From the extract: "Hubbard’s team discovered unfrozen saline zones, starting about two meters below the top of the permafrost and running many meters deep"

I hadn't heard of that before. So after the top meters thaw, we may be hitting many meters of 'pre-thawed' carbon ready to come out rather quickly. And then there are deeper pockets of free methane.

We can't know what the exact nature of the feedback will be, but it seems least likely to be what mh is suggesting.

[AbruptSLR]

wili,
As you say we may not be able to say the exact way that the permafrost will degrade, but it will be more complicated that m.h. implies as indicated by the following list of repeats posts that I have made about the mechanisms and implications of accelerated permafrost degradation beyond that considered in AR5:

(a) The linked referenced research is potentially very bad news as this indicates that the permafrost may produce large amounts of methane as it decomposes (potentially acting as a very strong positive feedback):

Rhiannon Mondav, Ben J. Woodcroft, Eun-Hae Kim, Carmody K. McCalley, Suzanne B. Hodgkins, Patrick M. Crill, Jeffrey Chanton, Gregory B. Hurst, Nathan C. VerBerkmoes, Scott R. Saleska, Philip Hugenholtz, Virginia I. Rich & Gene W. Tyson, (2014), "Discovery of a novel methanogen prevalent in thawing permafrost", Nature Communications, 5,3212doi:10.1038/ncomms4212
http://www.nature.com/ncomms/2014/140214/ncomms4212/full/ncomms4212.html

Abstract: "Thawing permafrost promotes microbial degradation of cryo-sequestered and new carbon leading to the biogenic production of methane, creating a positive feedback to climate change. Here we determine microbial community composition along a permafrost thaw gradient in northern Sweden. Partially thawed sites were frequently dominated by a single archaeal phylotype, Candidatus ‘Methanoflorens stordalenmirensis’ gen. nov. sp. nov., belonging to the uncultivated lineage ‘Rice Cluster II’ (Candidatus ‘Methanoflorentaceae’ fam. nov.). Metagenomic sequencing led to the recovery of its near-complete genome, revealing the genes necessary for hydrogenotrophic methanogenesis. These genes are highly expressed and methane carbon isotope data are consistent with hydrogenotrophic production of methane in the partially thawed site. In addition to permafrost wetlands, ‘Methanoflorentaceae’ are widespread in high methane-flux habitats suggesting that this lineage is both prevalent and a major contributor to global methane production. In thawing permafrost, Candidatus ‘M. stordalenmirensis’ appears to be a key mediator of methane-based positive feedback to climate warming."


See also:


http://www.abc.net.au/science/articles/2014/02/20/3948946.htm


(b) The linked reference indicates that newly studies factors indicate that greenhouse gas emissions from thawing permafrost will likely be more significant than previously expected:

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production by Suzanne B. Hodgkinsa,Malak M. Tfailya, Carmody K. McCalleyb, Tyler A. Loganc, Patrick M. Crilld, Scott R. Saleskab, Virginia I. Riche, and Jeffrey P. Chantona, published in PNAS on 7 April 2014. DOI: 10.1073/pnas.1314641111

http://www.pnas.org/content/early/2014/04/02/1314641111

Abstract: "Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH4) vs. carbon dioxide (CO2) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely unstudied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a ∼40-y permafrost thaw progression from recently- to fully thawed sites in Stordalen Mire (68.35°N, 19.05°E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH4 and CO2 production potentials, higher relative CH4/CO2 ratios, and a shift in CH4 production pathway from CO2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH4. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes."


(c) The linked reference provides evidence that CO₂ emissions from permafrost degradation will likely be higher than previously expected

Rose M. Cory, Collin P. Ward, Byron C. Crump, George W. Kling, (2014), "Sunlight controls water column processing of carbon in arctic fresh waters", Science, Vol. 345, no. 6199 pp. 925-928, DOI: 10.1126/science.1253119


http://www.sciencemag.org/content/345/6199/925


Abstract: "Carbon in thawing permafrost soils may have global impacts on climate change; however, the factors that control its processing and fate are poorly understood. The dominant fate of dissolved organic carbon (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Although both processes are most often attributed to bacterial respiration, we found that photochemical oxidation exceeds rates of respiration and accounts for 70 to 95% of total DOC processed in the water column of arctic lakes and rivers. At the basin scale, photochemical processing of DOC is about one-third of the total CO2 released from surface waters and is thus an important component of the arctic carbon budget."


See also:
http://www.laboratoryequipment.com/news/2014/08/sunlight-controls-fate-permafrosts-released-carbon

Extract: "… researchers show for the first time that sunlight, not microbial activity, dominates the production of carbon dioxide in Arctic inland waters.
"Our results suggest that sunlight, rather than biological processes, controls the fate of carbon released from thawing permafrost soils into Arctic surface waters," said aquatic geochemist Rose Cory, first author of the Science paper and an assistant professor in the U-M Department of Earth and Environmental Sciences.
Last year, the same team reported in PNAS that recently exposed carbon from thawed Alaskan permafrost is extremely sensitive to sunlight and can quickly be converted to carbon dioxide. Taken together, the two studies suggest that "we're likely to see more carbon dioxide released from thawing permafrost than people had previously believed," Cory said."

(d) The linked reference has a free access pdf, and indicates that the permafrost carbon feedback (PCF), is too low in all of the AR5 RCP scenarios; and that the PCF can increase the RCP 8.5 mean global temperature increase by also 8% by 2100:

Kevin Schaefer, Hugues Lantuit, Vladimir E Romanovsky, Edward A G Schuur and Ronald Witt, (2014), "The impact of the permafrost carbon feedback on global climate", Environ. Res. Lett. 9 085003, doi:10.1088/1748-9326/9/8/085003

http://iopscience.iop.org/1748-9326/9/8/085003

Abstract: "Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon dioxide (CO2) and methane (CH4) to influence global climate. The permafrost carbon feedback (PCF) is the amplification of surface warming due to CO2 and CH4 emissions from thawing permafrost. An analysis of available estimates PCF strength and timing indicate 120 ± 85 Gt of carbon emissions from thawing permafrost by 2100. This is equivalent to 5.7 ± 4.0% of total anthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 8.5 scenario and would increase global temperatures by 0.29 ± 0.21 °C or 7.8 ± 5.7%. For RCP4.5, the scenario closest to the 2 °C warming target for the climate change treaty, the range of cumulative emissions in 2100 from thawing permafrost decreases to between 27 and 100 Gt C with temperature increases between 0.05 and 0.15 °C, but the relative fraction of permafrost to total emissions increases to between 3% and 11%. Any substantial warming results in a committed, long-term carbon release from thawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting for permafrost emissions risks overshooting the 2 °C warming target. Climate projections in the IPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do not adequately account for emissions from thawing permafrost and the effects of the PCF on global climate. We recommend the IPCC commission a special assessment focusing on the PCF and its impact on global climate to supplement the AR5 in support of treaty negotiation."


(e) The linked reference finds that degrading permafrost will produce more methane and less carbon dioxide that current Earth System Models assume; which when corrected will significantly increase projections of Arctic amplification:

Zhaosheng Fan, Jason C. Neff, Mark P. Waldrop, Ashley P. Ballantyne, Merritt R. Turetsky, (2014), "Transport of oxygen in soil pore-water systems: implications for modeling emissions of carbon dioxide and methane from peatlands", Biogeochemistry, doi:10.1007/s1053-014-0012-0.

http://link.springer.com/article/10.1007%2Fs10533-014-0012-0#page-1

Abstract: "Peatlands store vast amounts of soil carbon and are significant sources of greenhouse gases, including carbon dioxide (CO2) and methane (CH4) emissions. The traditional approach in biogeochemical model simulations of peatland emissions is to simply divide the soil domain into an aerobic zone above and an anaerobic zone below the water table (WT) and then calculate CO2 and CH4 emissions based on the assumed properties of these two discrete zones. However, there are major potential drawbacks associated with the traditional WT-based approach, because aerobic or anaerobic environments are ultimately determined by oxygen (O2) concentration rather than water content directly. Variations in O2 content above and below the WT can be large and thus may play an important role in partitioning of carbon fluxes between CO2 and CH4. In this paper, we propose an oxygen-based approach, which simulates the vertical and radial components of O2 movement and consumption through the soil aerobic and anaerobic environments. We then use both our oxygen-based and the traditional WT-based approaches to simulate CO2 and CH4 emissions from an Alaskan fen peatland. The results of model calibration and validation suggest that our physically realistic approach (i.e., oxygen-based approach) cause less biases on the simulated flux of CO2 and CH4. The results of model simulations also suggest that the traditional WT-based approach might substantially under-estimate CH4 emissions and over-estimate CO2 emissions from the fen due to the presence of anaerobic zones in unsaturated soil. Our oxygen-based approach can be easily incorporated into existing ecosystem or earth system models but will require additional validation with more extensive field observations to be implemented within biogeochemical models to improve simulations of soil C fluxes at regional or global scale."

(f) The linked reference suggests that permafrost thawing is a possible source of the both the abrupt carbon release and the associated abrupt increase in mean global temperature at the onset of the Bolling/Allerod, and that a similar occurrence could happen with continued global warming:

Peter Köhler, Gregor Knorr and Edouard Bard, (2014), "Permafrost thawing as a possible source of abrupt carbon release at the onset of the Bølling/Allerød", Nature Communications 5:5520; DOI: 10.1038/ncomms6520

http://www.nature.com/ncomms/2014/141120/ncomms6520/full/ncomms6520.html

Abstract: "One of the most abrupt and yet unexplained past rises in atmospheric CO2 (>10 p.p.m.v. in two centuries) occurred in quasi-synchrony with abrupt northern hemispheric warming into the Bølling/Allerød, ~14,600 years ago. Here we use a U/Th-dated record of atmospheric Δ14C from Tahiti corals to provide an independent and precise age control for this CO2 rise. We also use model simulations to show that the release of old (nearly 14C-free) carbon can explain these changes in CO2 and Δ14C. The Δ14C record provides an independent constraint on the amount of carbon released (~125 Pg C). We suggest, in line with observations of atmospheric CH4 and terrigenous biomarkers, that thawing permafrost in high northern latitudes could have been the source of carbon, possibly with contribution from flooding of the Siberian continental shelf during meltwater pulse 1A. Our findings highlight the potential of the permafrost carbon reservoir to modulate abrupt climate changes via greenhouse-gas feedbacks."

See also:
http://www.reportingclimatescience.com/news-stories/article/did-permafrost-melt-cause-abrupt-ice-age-co2-rise.html

(g) The following linked article indicate the importance of ecosystem changes as positive feedback mechanisms.  The link discusses the role of the artic ground squirrels in accelerating permafrost loss:

Nigel Golden, Susan Natali and Nikita Zimov, (2014), "Consequences of artic ground squirrels on soil carbon loss from Siberian tundra", Fall AGU Conference

https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/20090

Abstract: "A large pool of organic carbon (C) has been accumulating in the Arctic for thousands of years. Much of this C has been frozen in permafrost and unavailable for microbial decomposition. As the climate warms and permafrost thaws, the fate of this large C pool will be driven not only by climatic conditions, but also by ecosystem changes brought about by arctic animal populations. In this project we studied arctic ground squirrels (Spermophilus parryii), which are widely-distributed throughout the Arctic. These social mammals create subterranean burrows that mix soil layers, increase aeration, alter soil moisture and temperature, and redistribute soil nutrients, all of which may impact microbial decomposition. We examined the effects of arctic ground squirrel activity on soil C mineralization in dry heath tundra underlain by continuous permafrost in the Kolyma River watershed in northeast Siberia, Russia. Vegetation cover was greatly reduced on the ground squirrel burrows (80% of ground un-vegetated), compared to undisturbed sites (35% of ground un-vegetated). Soils from ground squirrel burrows were also significantly dryer and warmer. To examine effects of ground squirrel activity on microbial respiration, we conducted an 8-day incubation of soil fromburrows and from adjacent undisturbed tundra. In addition, we assessed the impact of nutrient addition by including treatments with low and high levels of nitrogen addition. Microbial respiration (per gram soil) was three-fold higher in incubated soils from the undisturbed sites compared to soils collected from the burrows. The lower rates of respiration from the disturbed soils may have been a result of lower carbon quality or low soil moisture. High nitrogen addition significantly increased respiration in the undisturbed soils, but not in the disturbed burrow soils, which suggests that microbial respiration in the burrow soils was not primarily limited by nitrogen. These results demonstrate the importance of wildlife activity on soil C vulnerability in the Arctic. As C is moved from protected permafrost pools to thawed soils, burrowing animals, such as the arctic ground squirrel, may play an increasingly important role in regulating the transfer of C from soils to the atmosphere."


Best,
ASLR

[AbruptSLR]

The following is a continuation of my last post due to the 2,000 word post limit:
(h) The linked reference indicates that the longer growing season in the Arctic (largely due to polar amplification) is resulting in a greater abundance of deciduous shrubs in the tundra (as observed by satellites); which according to their models is increasing net carbon dioxide uptake.  However, while it may well be true that this deciduous shrub growth is serving as a temporary carbon dioxide sink, it is most likely only absorbing the extra carbon dioxide being emitted by the degradation of the permafrost, leaving the associated methane emissions in the atmosphere.  Furthermore, the change in albedo associated with the shrub growth is accelerating the permafrost degradation faster than the shrubs are serving as a carbon sink; which in a few decades will result in a net positive feedback mechanism.

Shannan K. Sweet, Kevin L. Griffin, Heidi Steltzer, Laura Gough and Natalie T. Boelman, (2014), "Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake", Global Change Biology, DOI: 10.1111/gcb.12852

http://onlinelibrary.wiley.com/doi/10.1111/gcb.12852/abstract

Abstract: "Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community specific leaf area index (LAI) model to estimate LAI throughout the green season, and a tundra specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake."

(i) The second to last sentence of the linked abstract is of some concern to increasing methane concentration in the atmosphere, i.e.:  "Sustained submergence into the future should increase gas venting rate roughly exponentially as sediments continue to warm."

J. M. Frederick, and B. A. Buffett, (2014), "Taliks in relict submarine permafrost and methane hydrate deposits: Pathways for gas escape under present and future conditions", Journal of Geophysical Research: Earth Surface, DOI: 10.1002/2013JF002987

http://onlinelibrary.wiley.com/doi/10.1002/2013JF002987/abstract

Abstract: "We investigate the response of relict Arctic submarine permafrost and gas hydrate deposits to warming and make predictions of methane gas flux to the water column using a 2-D multiphase fluid flow model. Exposure of the Arctic shelf during the last glacial cycle formed a thick layer of permafrost, protecting hydrate deposits below. However, talik formation below paleo-river channels creates permeable pathways for gas migration from depth. An estimate of the maximum gas flux at the present time for conditions at the East Siberian Arctic Seas is 0.2047 kg yr−1 m−2, which produces a methane concentration of 142 nM in the overlying water column, consistent with several field observations. For conditions at the North American Beaufort Sea, the maximum gas flux at the present time is 0.1885 kg yr−1 m−2, which produces a methane concentration of 78 nM in the overlying water column. Shallow sediments are charged with residual methane gas after venting events. Sustained submergence into the future should increase gas venting rate roughly exponentially as sediments continue to warm. Studying permafrost-associated gas hydrate reservoirs will allow us to better understand the Arctic's contribution to the global methane budget and global warming."
(j) The following link (with a free access pdf)/citation/abstract indicate that the current climate change models greatly underestimate the amount of methane being released by thawing permafrost in the Canadian Arctic, according to Canada's National Institute of Scientific Research (INRS), as indicated by the following quote from Karita Negandhi, a student at INRS:

"We discovered that although the small shallow ponds we studied represent only 44 percent of the water-covered surface in a Bylot Island valley, they generate 83 percent of its methane emissions,"

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0078204

Small Thaw Ponds: An Unaccounted Source of Methane in the Canadian High Arctic Karita Negandhi, Isabelle Laurion, Michael J. Whiticar, Pierre E. Galand, and Connie Lovejoy; Journal PLOS; Nov 13, 2013; DOI: 10.1371/journal.pone.0078204

Abstract
"Thawing permafrost in the Canadian Arctic tundra leads to peat erosion and slumping in narrow and shallow runnel ponds that surround more commonly studied polygonal ponds. Here we compared the methane production between runnel and polygonal ponds using stable isotope ratios, 14C signatures, and investigated potential methanogenic communities through high-throughput sequencing archaeal 16S rRNA genes. We found that runnel ponds had significantly higher methane and carbon dioxide emissions, produced from a slightly larger fraction of old carbon, compared to polygonal ponds. The methane stable isotopic signature indicated production through acetoclastic methanogenesis, but gene signatures from acetoclastic and hydrogenotrophic methanogenic Archaea were detected in both polygonal and runnel ponds. We conclude that runnel ponds represent a source of methane from potentially older C, and that they contain methanogenic communities able to use diverse sources of carbon, increasing the risk of augmented methane release under a warmer climate."

(k) Many commentators have noted that the retreat of Arctic Sea Ice may draw more shipping and more oil/gas development into the fragile Arctic Ocean; however, the linked article discusses the strong possibility that as the NH permafrost thaws farmers will move into this organic rich farmlands:

http://modernfarmer.com/2014/01/permafrost-farming-possible/

Note that these permafrost farms will accelerate the thawing of the permafrost, which could accelerate carbon emission from the organic currently frozen in the permafrost.

Best,
ASLR

[AbruptSLR]

wili,
Here are some other partial posts that I have made on the topic of permafrost degradation mechanisms that AR5 did not adequately consider:
1. The linked reference (with a free access pdf) indicates that the albedo of both melting snow and ice are affected at least two times more adversely than non-melting snow and ice by black carbon.  Therefore, as the polar areas continue warm-up the positive feedback from black carbon will likely increase:

Marks, A. A. and King, M. D.: The effect of snow/sea ice type on the response of albedo and light penetration depth (e-folding depth) to increasing black carbon, The Cryosphere Discuss., 8, 1023-1056, doi:10.5194/tcd-8-1023-2014, 2014.

http://www.the-cryosphere-discuss.net/8/1023/2014/tcd-8-1023-2014.html
Abstract: "The absence of boreal forests from global policy agendas on sustainable development and climate change mitigation represents a massive missed opportunity for environmental protection. The boreal zone contains some of the world's largest pools of terrestrial carbon that, if not safeguarded from a conversion to a net source of greenhouse gases, could seriously exacerbate global climate change. At the same time, boreal countries have a strong tradition of forest management—expertise that could be effectively leveraged toward global and national carbon mitigation targets and sustainable development. Current obstacles against such contributions include weak incentives for carbon sequestration and a reluctance to embrace change by forest managers and policy makers. We discuss possible solutions to overcome these obstacles, including the improvement of ineffective incentives, the development of alternative forest management strategies, and the need to maintain ecosystem resilience through the pursuit of policy and management options."


See also the extract from the following link:

http://news.mongabay.com/2014/0604-sutherland-taiga.html

Extract: "According to Jon Moen, an author of the report, a failure of global climate change policies to properly support boreal forests could prompt forests to emit more carbon than they consume, potentially contributing significantly to increased global temperatures.

“The scary part is if the thawing permafrost, increased fires, drought and insect attacks release the carbon that is stored in the boreal zone, we might see temperatures increase even more,” Moen said."
2. The linked reference makes it clear that the boreal forests (in the taiga, see the attached image for the extent) are at greater risk of destruction than previously realized, most significantly due to the thawing of the permafrost, which promotes fires, droughts and insect attack.  Not only would this destruction turn a large CO₂ sink into a CO₂ source, but would also eliminate a major source of aerosols emitted by the boreal forests which facilitate cloud formation (which reflects sunlight and reduces global warming):

Moen, J., Rist, L., Bishop, K., Chapin, F. S., Ellison, D., Kuuluvainen, T., Bradshaw, C. J. (2014), "Eye on the taiga: removing global policy impediments to safeguard the boreal forest", Conservation Letters, DOI: 10.1111/conl.12098
3. The linked article about current Canadian wildfires indicate that the current weather pattern contributing to the wildfires were not predicted by the GCMs to occur for another 40-yrs:

http://www.adn.com/article/20140717/worst-wildfire-season-decades-canada-s-northwest-territories
4. The linked reference indicates that the Earth System Sensitivity, ESS, may be bigger than previously thought; however, it does not indicate how quickly the positive feedback from the synchronization of the North Pacific and North Atlantic climates:

Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

http://www.sciencemag.org/content/345/6195/444
5. The linked reference (with a free access pdf) provides evidence that the main source of uncertainty for Arctic climate variability, and its predictability, is the North Pacific.  As we know that the North Pacific is projected to warm-up over the next 25 years in order to synchronize with the North Atlantic, it seems likely that we can expect the Arctic to warm rapidly as the North Pacific warms:

Dmitry V. Sein, Nikolay V. Koldunov, Joaquim G. Pinto, William Cabos, (2014), "Sensitivity of simulated regional Arctic climate to the choice of coupled model domain", Tellus A, 66, 23966, http://dx.doi.org/10.3402/tellusa.v66.23966

http://www.tellusa.net/index.php/tellusa/article/view/23966

6. The linked 2013 article focuses on changes in the Arctic Ocean, and indicates that changes in the plankton there could result in a positive feedback (that will likely become more important with time) associated both with lower dimethyl sulphide production and lower CO2 absorption: 

http://www.egu.eu/news/76/tiny-plankton-could-have-big-impact-on-climate/

7. The reference cited below indicates that atmospheric hydroxyl-radical concentrations are about the same in the Northern and Southern Hemispheres.  This is bad news as it implies that methane emissions in the Northern Hemisphere are likely higher than researchers have previously assumed (as it was expected that the Northern Hemisphere would have more hydroxyl-radicals than the Southern Hemisphere, and it appears likely that greenhouse gases such as methane are consuming part of store of atmospheric hydroxyl-radicals in the Northern Hemisphere).

P. K. Patra, M.C. Krol, S. A. Montzka, T. Arnold, E. L. Atlas, B.R. Lintner, B.B. Stephens, B. Xiang, J. W. Elkins, P. J. Fraser, A. Ghosh, E. J. Hintsa, D. F. Hurst, K. Ishijima, P. B. Krummel, B.R. Miller, K. Miyazaki, F.L. Moore, J. Mühle, S. O’Doherty, R.G. Prinn, L.P. Steele, M. Takigawa, . J. Wang, R.F. Weiss, S.C. Wofsy, and D. Young, (2014), "Observational evidence for interhemispheric hydroxyl-radical parity", Nature, doi:10.1038/nature13721


http://www2.ucar.edu/atmosnews/just-published/12346/wheres-atmospheres-self-cleaning-power

Best,
ASLR

[AbruptSLR]

As my three prior posts on the subject of permafrost degradation mechanisms may well be too much information (making it hard to see the forest from the trees), I provide this last post as a rough approximation that errs on the side of least drama just to be understandable:
The first attached image is from NOAA and the National Snow and Ice Data Center (NSIDC), 2011, showing an old estimate (prior to AR5) of the cumulative carbon emissions with time estimated to come from global permafrost degradation (see the caption below).  I that one short ton of carbon is equivalent to 3.66 short tons of carbon dioxide or 3.32 metric tonnes of carbon dioxide; thus if all of the carbon release from the permafrost were carbon dioxide then in 2009 this amount of carbon dioxide released by the permafrost was approximately 660 million metric tonnes/year as compared to the 30,400 million metric tonnes of man-made emissions in 2009, or 2% of manmade emissions for that year. However, by 2045 the permafrost emissions are projected to be approximately 4,500 million metric tonnes of carbon dioxide/year; which, if manmade carbon emissions were to remain at the 2009 levels, would represent approximately 15% of manmade emissions (however, as discussed previously some of this carbon would be released as methane rather than as carbon dioxide, and as methane is 105-times as active a greenhouse gas as carbon dioxide, or a 20-year period, the percentage of equivalent carbon dioxide produced by the permafrost in 2045 would be closer to 20%) .

Caption: "Projected Permafrost Carbon Flux (atmospheric emission in billions of short tons per year) from the Permafrost with Time."

Furthermore, the second attached image shows an old ESM projection of the influence on Arctic Amplification of rapid Arctic Sea Ice loss vs traditional (AR4) estimates of Arctic Sea Ice loss.  The extra Arctic Amplification will clearly accelerate permafrost degradation.

Best,
ASLR

[AbruptSLR]

"The heat for the percolating water still has to come from the surface?"

That surface can be very far away, where the rain evaporated in the first place.

To add to your point that rainfall in the polar regions will increase with more global warming, which will convey sub-polar energy into the polar regions (more significantly into the Arctic as indicated by the teleconnections shown in the first attached image); but also as indicated by the linked reference, CMIP5 (used by AR5) underestimates extreme hydrological events (as indicated by global hydrological models) that can telecommunicate large amounts of both rain and energy into the polar regions

Giuntoli, I., Vidal, J.-P., Prudhomme, C., and Hannah, D. M.: Future hydrological extremes: the uncertainty from multiple global climate and global hydrological models, Earth Syst. Dynam. Discuss., 6, 1-30, doi:10.5194/esdd-6-1-2015, 2015.

http://www.earth-syst-dynam-discuss.net/6/1/2015/esdd-6-1-2015.html

Abstract. Projections of changes in the hydrological cycle from Global Hydrological Models (GHMs) driven by Global Climate Models (GCMs) are critical for understanding future occurrence of hydrological extremes. However, uncertainties remain large and need to be better assessed. In particular, recent studies have pointed to a considerable contribution of GHMs that can equal or outweigh the contribution of GCMs to uncertainty in hydrological projections. Using 6 GHMs and 5 GCMs from the ISI-MIP multi-model ensemble, this study aims: (i) to assess future changes in the frequency of both high and low flows at the global scale using control and future (RCP8.5) simulations by the 2080s, and (ii) to quantify, for both ends of the runoff spectrum, GCMs and GHMs contributions to uncertainty using a 2-way ANOVA. Increases are found in high flows for northern latitudes and in low flows for several hotspots. Globally, the largest source of uncertainty is associated with GCMs, but GHMs are the greatest source in snow dominated regions. More specifically, results vary depending on the runoff metric, the temporal (annual and seasonal) and regional scale of analysis. For instance, uncertainty contribution from GHMs is higher for low flows than it is for high flows, partly owing to the different processes driving the onset of the two phenomena (e.g. the more direct effect of the GCMs precipitation variability on high flows). This study provides a comprehensive synthesis of where future hydrological extremes are projected to increase and where the ensemble spread is owed to either GCMs or GHMs. Finally, our results underline the importance of using multiple GCMs and GHMs to envelope the overall uncertainty range and the need for improvements in modeling snowmelt and runoff processes to project future hydrological extremes."

[AbruptSLR]

Also, I thought that I would note that abrupt SLR due to the likely collapse of the WAIS by 2100 following RCP 8.5, will likely result in positive feedbacks not considered by AR5 including ASLR will:
(a) inundate significant areas of low-lying Arctic coastal permafrost areas; which, could cause a short-term spike in CO₂ emissions associated with local permafrost;
(b) push warm Pacific waters into the Arctic Ocean thus increasing Arctic Amplification and methane hydrate decomposition; and
(c) as indicated by the following abstract from Potential methane reservoirs beneath Antarctica by Wadham et al 2012, in Nature, could result in methane hydrate decomposition from Antarctica (see attached image):

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 carbon. 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 thick 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 model 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."

Extract from an associated web article: "British co-author Prof Jemma Wadham, from the University of Bristol, said: "This is an immense amount of organic carbon, more than 10 times the size of carbon stocks in northern permafrost regions.
"Our laboratory experiments tell us that these sub-ice environments are also biologically active, meaning that this organic carbon is probably being metabolised into carbon dioxide and methane gas by microbes."  The amount of frozen and free methane gas beneath the ice sheets could amount to 4bn tonnes, the researchers estimate.  Wadham also said: “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”.   This implies that some of these methane from destabilized hydrates below the WAIS and the EAIS could be released via the methane saturated basal meltwater just by pressure reduction associated with the thinning of the ice sheets, without the subglacial sediments being exposed by either subglacial cavities due to the advection of warm CDW, or other grounding line retreat."

[AbruptSLR]

The linked reference shows that anthropogenic aerosols have been masking/damping Arctic Amplification even more than it has been masking/damping the increase in mean global surface temperature.  Thus as aerosols are cleaned-up the Arctic will warm faster than previously estimated (which will also degrade the permafrost faster than previously estimated):

Najafi, M.R., et al. (2015) Attribution of Arctic temperature change to greenhouse-gas and aerosol influences, Nature Climate Change, doi:10.1038/nclimate2524

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2524.html

Abstract: "The Arctic has warmed significantly more than global mean surface air temperature over recent decades, as expected from amplification mechanisms. Previous studies have attributed the observed Arctic warming to the combined effect of greenhouse gases and other anthropogenic influences. However, given the sensitivity of the Arctic to external forcing and the intense interest in the effects of aerosols on its climate, it is important to examine and quantify the effects of individual groups of anthropogenic forcing agents. Here we quantify the separate contributions to observed Arctic land temperature change from greenhouse gases, other anthropogenic forcing agents (which are dominated by aerosols) and natural forcing agents. We show that although increases in greenhouse-gas concentrations have driven the observed warming over the past century, approximately 60% of the greenhouse-gas-induced warming has been offset by the combined response to other anthropogenic forcings, which is substantially greater than the fraction of global greenhouse-gas-induced warming that has been offset by these forcings. The climate models considered on average simulate the amplitude of response to anthropogenic forcings well, increasing confidence in their projections of profound future Arctic climate change."

See also (both extract and image):

http://www.carbonbrief.org/blog/2015/02/aerosols-dampen-pace-of-arctic-warming-for-now-say-scientists/

Extract: "And the results suggest the cooling effect from aerosols is much larger in the Arctic than elsewhere in the world, Najafi adds. A separate study finds aerosols were responsible for offsetting around five per cent of global greenhouse gas warming between 1901 and 2010, and around 27 per cent for the shorter period of 1951 to 2010.
In the coming decades, human-caused emissions of aerosols are projected to decrease, but greenhouse gases are expected to continue to rise. This could mean the rate of Arctic warming increases, says Najafi:
"Projections based on climate model simulations using a high emission scenario suggest that Arctic temperatures might rise by 8.3 degrees by the end of the century."
The new research shows that while aerosols are offsetting some warming in the remote North, it's unlikely to stay that way. We're seeing changes in the Arctic already and picking up the pace of warming is likely to have serious implications for wildlife and even Northern Hemisphere weather."

Edit, the following is the caption for the second attached image: "Observed 5-yr mean Arctic mean temperature anomalies (black) are compared with the mean simulated response to all anthropogenic and natural forcings (red), greenhouse-gas changes (green), other anthropogenic forcings (orange) and natural forcings (blue). Red shading and blue dashed lines represent the 5–95% uncertainty ranges corresponding to ALL and NAT responses respectively."

[AbruptSLR]

The linked reference uses paleo-evidence (see attached image) to link tectonic activity with the acceleration of Arctic seafloor methane seeps associated with methane hydrate decomposition.  Obviously, abrupt SLR possibly of over 3m this century would put a lot of stress on tectonic plates world-wide; which should not only increase earthquakes but should also accelerate the decomposition of subsea marine methane hydrates (also due to local ocean water temperature increases due to changes in seafloor currents):

Plaza-Faverola, A., S. Bünz, J. E. Johnson, S. Chand, J. Knies, J. Mienert, and P. Franek (2015), Role of tectonic stress in seepage evolution along the gas hydrate-charged Vestnesa Ridge, Fram Strait, Geophys. Res. Lett., 42, doi:10.1002/2014GL062474.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL062474/abstract;jsessionid=EF4FFE46D2AFCA7B7A659D07503105BF.f04t03

Abstract: "Methane expulsion from the world ocean floor is a broadly observed phenomenon known to be episodic. Yet the processes that modulate seepage remain elusive. In the Arctic offshore west Svalbard, for instance, seepage at 200–400 m water depth may be explained by ocean temperature-controlled gas hydrate instabilities at the shelf break, but additional processes are required to explain seepage in permanently cold waters at depths >1000 m. We discuss the influence of tectonic stress on seepage evolution along the ~100 km long hydrate-bearing Vestnesa Ridge in Fram Strait. High-resolution P-Cable 3-D seismic data revealed fine-scale (>10 m width) near-vertical faults and fractures controlling seepage distribution. Gas chimneys record multiple seepage events coinciding with glacial intensification and active faulting. The faults document the influence of nearby tectonic stress fields in seepage evolution along this deepwater gas hydrate system for at least the last ~2.7 Ma."

See also:

http://www.sciencedaily.com/releases/2015/02/150205101921.htm


http://www.ibtimes.co.uk/deep-sea-methane-emissions-occurring-millions-years-says-study-1487279


Edit: Also see:
http://forum.arctic-sea-ice.net/index.php/topic,283.0.html#lastPost

[Lennart van der Linde]

Our carbon target should not be based on climate science, but a political assessment of what is tough but possible.

Hansen et al 2013 made their assessment (both scientific and political) and think 130 GtC should be the remaining budget: tough, but possible, they think, and I agree. Of course politically this is not close to being feasible yet. But if more people support such a target, and organize to put pressure on the relevant politicians, then there may still be a small chance to make it feasible.

What would your political assessment be? What carbon budget shoud we choose, politically, if it should be more specific than 'as low as possible' (I agree): 100, 200, 300 GtC, or even more?

[wili]

ASLR wrote: "SLR possibly of over 3m this century would put a lot of stress on tectonic plates world-wide; which should not only increase earthquakes but should also accelerate the decomposition of subsea marine methane hydrates (also due to local ocean water temperature increases due to changes in seafloor currents)"

And here I had always thought that perhaps the only marginally positive thing about aslr is that it would put increased pressure on seabed clathrates and so make them less likely to dissociate. I hadn't thought about the tectonic pressures involved, or rather I had but now about how that might lead to more subsea seismic activity that would likely destabilize and free up methane, both frozen in hydrates and in deeper deposits. 

[AbruptSLR]

I do not have access to the full article (as it is behind a pay-wall); however, the linked abstract indicates that the "Nonlinear Ensemble Parameter Perturbation" method can provide insight into the climate sensitivities projected by climate models.  Perhaps anyone with a subscription could verify the nature of the projected changes to the calculated climatology.

Xudong Yin, Juanjuan Liu, and Bin Wang, 2015: Nonlinear Ensemble Parameter Perturbation for Climate Models. J. Climate, 28, 1112–1125., doi: http://dx.doi.org/10.1175/JCLI-D-14-00244.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00244.1

Abstract: "Model parameters can introduce significant uncertainties in climate simulations. Sensitivity analysis provides a way to quantify such uncertainties. Existing sensitivity analysis methods, however, cannot estimate the maximum sensitivity of the simulated climate to perturbations in multiple parameters. This study proposes the concept of nonlinear ensemble parameter perturbation (NEPP), which is independent of model initial conditions, to estimate the maximum effect of parameter perturbations on simulating Earth’s climate. The NEPP is obtained by solving a maximization problem, whose cost function is defined by the maximum deviation of a unique ensemble of short-term predictions with large enough members caused by parameter perturbations and whose optimal solution is obtained by an ensemble-based gradient approach. This method is used to investigate the effects of NEPP on the climate of the Lorenz-63 model and a complex climate model, the Grid-Point Atmospheric Model of IAP LASG, version 2 (GAMIL2). It is found that the NEPP is capable of estimating the maximum change in climate simulation caused by perturbations in multiple parameters when the Lorenz-63 model is used. With a low computational cost, the NEPP can cause remarkable changes in the climatology of GAMIL2. The results also illustrate that the effects of parameter perturbations on short-term weather predictions and those on long-term climate simulations are correlated."

[AbruptSLR]

As the two linked RTCC (Responding to Climate Change) article indicate there will likely never be an AR6, but instead the IPCC will likely developed slimmed down annual climate science and review reports in order to provide policy makers with more timely and focused guidance:

http://www.rtcc.org/2015/02/11/slim-down-climate-science-reports-to-boost-impact-ipcc-told/

http://www.rtcc.org/2015/02/10/ipcc-could-conduct-annual-climate-review-says-pachauri/

Hopefully, such annual reports (which will be discuss in Kenya later this month) will work to address many of the short-comings associated with AR5.

[AbruptSLR]

The first attached figure (see caption below) shows the IPCC AR5 Northern Hemisphere snow cover extent projections, showing declining trends with increasing global warming

https://www.ccin.ca/home/ccw/snow/future/modelling

Caption for First Image: "Northern Hemisphere snow cover extent (Spring) historical and modelled future trends. Historical trends represented by black line; future projections (coloured lines) depict average from multiple models using RCP (Representative Concentration Pathways) scenarios (IPCC, 2013)."

While the linked pdf (provided by M.H.) indicates that the rate of the reduction in June Northern Hemisphere snow extent (-17.6% per decade) is exceeding the AR5 projected rate of change for the annual snow coverage extent (while this is not a surprise the summer months affect albedo more than the winter months (see the third attached plot of expected seasonal snow extent and deviations).

https://www.wmo.int/pages/prog/www/OSY/Meetings/GCW-PS1/Doc6.3_ArcticSnowCover_Monitoring.pdf

[AbruptSLR]

The following extracts from AR5 2013, cite caveats w.r.t. to the possible collapse of Antarctic marine glaciers and their impact on the AR5 SLR projections.  Note that their medium confidence caveat that a collapse of such marine glaciers would only contribute several tenths of a meter by 2100; however, if we continue on an RCP 8.5 pathway, I believe that the Pollard et al 2015 and the DeConto & Pollard 2014 work indicates that this abrupt contribution to SLR could be well over 1m by 2100:
 
- “Only the collapse of the marine-based sectors of the Antarctic ice sheet, if initiated, could cause GMSL to rise substantially above the likely range during the 21st century. This potential additional contribution cannot be precisely quantified but there is medium confidence that it would not exceed several tenths of a meter of sea level rise”.
- “In summary, ice-dynamics theory, numerical simulations, and paleo records indicate that the existence of a marine-ice sheet instability asso­ciated with abrupt and irreversible ice loss from the Antarctic ice sheet is possible in response to climate forcing. However, theoretical consid­erations, current observations, numerical models, and paleo records cur­rently do not allow a quantification of the timing of the onset of such an instability or of the magnitude of its multi-century contribution.”

[AbruptSLR]

While this is not an extremely well viewed thread (possibly because most people have already made-up their minds one-way or another); nevertheless, I think that it is valuable to realize that only one pathway for radiative forcing through 2100 will be followed, and relying on an outdated and incomplete PDF for global warming will not protect the youth of today and tomorrow from the true probability of climate hazards in the coming decades.  As we continue following a BAU pathway the shape of the PDF both shifts to the right and becomes more right skewed every day, so any carbon budget that James Hansen provided last year likely needs to be reduced today.

For example, heavy anthropogenic radiative forcing began in the 1970's, but due to the thermal inertia of the ocean, for the past 40 to 45 years the trend line for increasing ocean heat content in the upper 0 to 2000m of the ocean has essentially been linear (see the first attached plot). However, now that the impact of current radiative forcing to the oceans is super-imposed on the radiative forcing from the past decades, the rate of ocean heat uptake is accelerating (note in the first attached NOAA plot, the vertical scale had to be increased to accommodate the recent acceleration, and the scale will have to be increased every year now for some time to come).

For another example, decision makers are very proud that they enacted the Montreal Protocol that eventually limited CFC emissions, and they believe that someday they will do the same for the new threat of HFC emissions (see the second attached plot).  While the USA and China have agreed to restrict HFC emissions, the fastest growth is currently in South/Southeast Asia and Africa, where regulation of HFC emissions are currently very weak.  Thus if the UN takes a couple of decades to enact new controls on HFC's and it takes a decade or two to get South/Southeast Asia and Africa to implement such emissions, we could see the equivalent of 10Gt CO2 equivalent per year of HFC emissions by 2040, which is almost equal to all of our CO2 emissions in 2010.

Therefore, I think it is good to keep one's eyes open and to regularly update our preconceived PDFs for climate risk, as I find the argument distasteful that following RCP 8.5 until 2100 is impossible because society will collapse long before 2100 so we should all just continue with Business as Usual because RCP 8.5 is impossible.  Who cares whether following RCP 8.5 to 2100 is possible, or not, if society collapses in the meantime?

[AbruptSLR]

For those who do not understand how PDF (Probability Distribution/Density Functions) can be updated I provide the first attached figure showing plots for the change-point analysis for the annual heat wave count series in Mont, France, from 1949 to 2009, from Chu and Zhao, 2011.  This figure shows how frequency counts of temperature records can easily be used to update PDFs in this case which shifts to the right and becomes more right skewed.

Furthermore, the second attached image from Hansen et al 2012, show that this rightward shifting and skewing of the PDFs has been occurring for decades now, and useless we do something now, this trend will accelerate.

"All tyranny needs to gain a foothold is for people of good conscience to remain silent." Thomas Jefferson

[wili]

ASLR, I just want to say how valuable your contributions are here. I don't always have the time or skill to fully understand everything you post, but I definitely don't have the time or patience you show to come through the literature for relevant articles and present to us the juiciest bits.

So thanks, and keep up the good work.

My humble contribution (though of marginal relevance here, perhaps) is this handy graph from a recent SkS post that I have also linked to elsewhere: https://www.skepticalscience.com/Why_the_Miocene_Matters.html#commenthead

Different parts of the climate system respond at different rates. Based on Schmidt, 2012 & Zeebe, 2012.

I notice that it is the fast feedbacks that have the kind of behavior that mh was talking about. The slower carbon, ocean and icesheet feedbacks build up over time until the methane or ice sheet is gone, that is. Note that the feedback that takes the longest to have a significant effect, rock weathering, is also the only one that is consistently a negative, damping feedback. So it won't be in any hurry to come to our rescue.

[AbruptSLR]

There are many different versions/generations of Earth Systems Models.  Thus saying that an earlier version of the Community Earth System Model, was included in CMIP5 does not mean that we have the final answer in hand from AR5.  Indeed, the ACME project lead by the DOE (and which will not be complete for another 10 years) is based on (started from) the Community Earth System Model, but will be further developed for the DOE mission and computers.

I am hoping that ACME will provide sufficient guidance to allow decision makers to make reasonably well informed decisions.  Until then (& even after then) we will need to make the best decisions that we can with the information that we have; understanding that decision makers with a high tolerance for risk will push the envelope perhaps further than what is good for the global community/environment.

But the models will not have changed very much from where they were for CMIP 5. 

And if a model did make a small change in this timeframe that mattered for climate sensitivity, or for transient climate response over the next 100 years then, either the scientists writing up the research are incompetent or party to a conspiracy of silence, or there is no interesting change and the scientist writes up about a detail such as a change in the Jetstream position as the most interesting result of the recent modelling study.

You are wrong, as the linked information confirms that ACME will make major changes to CESM:

http://newscenter.lbl.gov/2014/08/25/acme/
http://climatemodeling.science.energy.gov/
http://climatemodeling.science.energy.gov/sites/default/files/publications/acme-project-strategy-plan_0.pdf
http://climatemodeling.science.energy.gov/sites/default/files/publications/acme-project-strategy-plan.pdf
http://science.energy.gov/~/media/sc-1/pdf/2012/Dehmer_2016_Budget_Presentation.pdf
http://crf.sandia.gov/acme-climate-modeling-powered-by-doe-supercomputers-tamed-by-uncertainty-quantification/

The linked (open access) reference provides a comparison of the best Earth Systems Model run to date (CESM-H), and a standard ESM run (CESM-S) such as that used for AR5.  The article (a must read), the attached image (and caption) and extracts, make it very clear that while the CESM-H run is not perfect (i.e. there is still a reason to build and run ACME), it is a substantial improvement about the AR5 generation of climate models, and it projects higher increases in mean global temperature increases, and less sea ice (see the figure 1) than the AR5 generation of projections.

I encourage others to look at the full article as I cannot do justice it in this post:

R. Justin Small, Julio Bacmeister, David Bailey, Allison Baker, Stuart Bishop, Frank Bryan, Julie Caron, John Dennis, Peter Gent, Hsiao-ming Hsu, Markus Jochum, David Lawrence, Ernesto Muñoz, Pedro diNezio, Tim Scheitlin, Robert Tomas, Joseph Tribbia, Yu-heng Tseng, & Mariana Vertenstein, (December 2014), "A new synoptic scale resolving global climate simulation using the Community Earth System Model", JAMES, Volume 6, Issue 4, Pages 1065–1094, DOI: 10.1002/2014MS000363

http://onlinelibrary.wiley.com/enhanced/doi/10.1002/2014MS000363/

Abstract: "High-resolution global climate modeling holds the promise of capturing planetary-scale climate modes and small-scale (regional and sometimes extreme) features simultaneously, including their mutual interaction. This paper discusses a new state-of-the-art high-resolution Community Earth System Model (CESM) simulation that was performed with these goals in mind. The atmospheric component was at 0.25° grid spacing, and ocean component at 0.1°. One hundred years of “present-day” simulation were completed. Major results were that annual mean sea surface temperature (SST) in the equatorial Pacific and El-Niño Southern Oscillation variability were well simulated compared to standard resolution models. Tropical and southern Atlantic SST also had much reduced bias compared to previous versions of the model. In addition, the high resolution of the model enabled small-scale features of the climate system to be represented, such as air-sea interaction over ocean frontal zones, mesoscale systems generated by the Rockies, and Tropical Cyclones. Associated single component runs and standard resolution coupled runs are used to help attribute the strengths and weaknesses of the fully coupled run. The high-resolution run employed 23,404 cores, costing 250 thousand processor-hours per simulated year and made about two simulated years per day on the NCAR-Wyoming supercomputer “Yellowstone.”"


Extracts: "The high-resolution CESM was run under “present-day” (year 2000) greenhouse gas conditions (fixed CO2 concentration of 367 ppm). This was chosen so that direct comparisons could be made with recent-era observations of fine-scale and large-scale phenomena. The prognostic carbon-nitrogen cycle was not used in this simulation.

In the following, this simulation will be referred to as CESM-High Resolution (CESM-H).
…
The interpretation of the model data employed in this paper is that the CESM-H and CESM-S are the best simulations available at their respective resolutions, for the same model version, and for year 2000 conditions."


Caption for Figure 1: "Time series of globally averaged quantities for 100 years of CESM-H (thick black line) and 166 years of CESM-S (thin gray line). (a) Top of atmosphere net radiation, positive incoming to Earth. Data are 10 year running mean. (b) Surface (including ocean, land, ice) temperature, 10 year running average. Sea ice area in (c) Northern Hemisphere and (d) Southern Hemisphere. (e) Atlantic Meridional Overturning Circulation (AMOC), 12 month running averages, (f) transport through Drake Passage due to Antarctic Circumpolar Current (ACC), annual values."

The following link provides public access to various model run outputs:

http://www.earthsystemgrid.org/

[sidd]

thanks for the link to CESM-H, but i must say we have a loooong way to go ...

[AbruptSLR]

thanks for the link to CESM-H, but i must say we have a loooong way to go ...

sidd,

When modeling non-linear chaotic systems it is always hard to separate model signal from bias (& noise) and the CESM-H projections are no exception.  Nevertheless, I believe that the authors show that their high resolution model may have less bias than the AR5 generation of models, and likely errs less on the side of least drama than does the AR5 projections.  When you point-out that there is a long-ways to go before we get access to the type of model projections that policy makers (who make all their decisions on the margin) want; I fully agree that at the earliest we will not have that answer for ten years when the ACME project completes its mission.

Furthermore, the 367 ppm CO2 forcing used in the model occurred in the 2004 to 2005 timeframe so this supports the idea that ECS may well be in the 4 to 4.5 C range (as per Sherwood et al 2014).

Finally, with regards to the reduction in Antarctic sea ice extent projected by CESM-H, according to the linked article (from the Antarctic folder) a slow response mechanism from the Antarctic ozone hole formation (some three decades ago) should now be strong enough to startdecreasing the extent of the Antarctic sea ice extent (particularly in the austral summer). The reference (with an open access pdf) indicates that two coupled climate models show that in response to an ozone depletion the Southern Ocean responded with two processes for sea ice extent change.  The first process based on a northward Ekman drift occurred relatively quickly and served to expand Antarctic sea ice extent about three decades ago.  The second process acted relatively more slowly (years to decades), results in a warming trend for the Southern Ocean leading to a reduction in projected sea ice extent (see attached figure).  Based on these findings we can expect Antarctic amplification to begin accelerating in the next decade or so (as indicated by the CESM-H results).

David Ferreira, John Marshall, Cecilia M. Bitz, Susan Solomon, and Alan Plumb, 2015: "Antarctic Ocean and Sea Ice Response to Ozone Depletion: A Two-Time-Scale Problem". J. Climate, 28, 1206–1226, doi: http://dx.doi.org/10.1175/JCLI-D-14-00313.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00313.1

http://www.met.rdg.ac.uk/~gf905417/Publications_files/Twotimescale_final.pdf



Abstract: "The response of the Southern Ocean to a repeating seasonal cycle of ozone loss is studied in two coupled climate models and is found to comprise both fast and slow processes. The fast response is similar to the interannual signature of the southern annular mode (SAM) on sea surface temperature (SST), onto which the ozone hole forcing projects in the summer. It comprises enhanced northward Ekman drift, inducing negative summertime SST anomalies around Antarctica, earlier sea ice freeze-up the following winter, and northward expansion of the sea ice edge year-round. The enhanced northward Ekman drift, however, results in upwelling of warm waters from below the mixed layer in the region of seasonal sea ice. With sustained bursts of westerly winds induced by ozone hole depletion, this warming from below eventually dominates over the cooling from anomalous Ekman drift. The resulting slow time-scale response (years to decades) leads to warming of SSTs around Antarctica and ultimately a reduction in sea ice cover year-round. This two-time-scale behavior—rapid cooling followed by slow but persistent warming—is found in the two coupled models analyzed: one with an idealized geometry and the other with a complex global climate model with realistic geometry. Processes that control the time scale of the transition from cooling to warming and their uncertainties are described. Finally the implications of these results are discussed for rationalizing previous studies of the effect of the ozone hole on SST and sea ice extent."

Best,
ASLR

[AbruptSLR]

I am re-posting the following from Csnavywx's reply in the Mauna Loa CO2 thread:

"I took another look at 5-year moving averages, this time using CO2e. I think that the increase in CO2e from year to year going forward will be a better measure of the rate of increase in radiative forcing mostly due to the fact that aerosols should be on a flat to slowly declining trend at this time (especially since China seems to be implementing its plans for scrubbing SO2 from plant stacks).

The 5-year moving average for CO2e is currently ~2.83 ppm/yr."

As we are now over 400ppm CO2 and CO2e is increasing at a rate of about 2.83 ppm/yr, I can see why the NRC is so concerned that it wants more funding to study geoengineering; as on the face of it, without sucking GHG from the atmosphere (ala bioenergy) we may well be headed towards the 9 C mean global temperature rise discussed at the following link:

http://forum.arctic-sea-ice.net/index.php/topic,1020.200.html

[AbruptSLR]

ASLR, I just want to say how valuable your contributions are here. I don't always have the time or skill to fully understand everything you post, but I definitely don't have the time or patience you show to come through the literature for relevant articles and present to us the juiciest bits.

So thanks, and keep up the good work.

My humble contribution (though of marginal relevance here, perhaps) is this handy graph from a recent SkS post that I have also linked to elsewhere: https://www.skepticalscience.com/Why_the_Miocene_Matters.html#commenthead

Different parts of the climate system respond at different rates. Based on Schmidt, 2012 & Zeebe, 2012.

I notice that it is the fast feedbacks that have the kind of behavior that mh was talking about. The slower carbon, ocean and icesheet feedbacks build up over time until the methane or ice sheet is gone, that is. Note that the feedback that takes the longest to have a significant effect, rock weathering, is also the only one that is consistently a negative, damping feedback. So it won't be in any hurry to come to our rescue.

wili,

Thanks for the contribution to help classify, the different types, and response times for different feedbacks.  While such guidelines are useful as rules of thumb, I would like to warn all readers that such rules of thumb were developed primarily from paleo-investigations with the Earth Systems near equilibrium, and they are also subject to bias by the individual doing the classification.  For example, the first attached image shows a comparable graphic but it shows the Upper Ocean responding in years to decades (which is faster than your graphic), and it also shows that vegetation and carbon cycles can be activated in the timeframe of decades (which also is more aggressive than your graphic).  Other items that readers should bear in mind include:
(a) Such graphics assume that the GHG is emitted (typically doubled) instantaneously; however, as the Small et al 2014 paper shows our current case has not yet reached equilibrium from earlier GHG emissions (i.e. Small et al show that the CO2 concentration of 367 ppm can result in an additional 1.2 C temp increase), and the effect of the earlier emissions must be added to the new emissions.
(b) As we have all discussed many of the "slow response" feedbacks can be accelerated by rapid rates of forcing such as by the WAIS collapse, permafrost degradation, & the introduction of warm water near the Arctic, and Southern, Oceans seafloor that can release methane rapidly from hydrates (note that rapid release of methane results in higher GWP (global warming potential) for methane).

My second attached figure shows another example of a common rule of thumb used by scientist who prefer to err on the side of least drama, in order to explain the difference of Transient Climate Response, TCR (which are largely linear), from Equilibrium Climate Sensitivity, ECS (which have substantial non-linearity).  Such figures fail to show and confidence ranges, and if Drew Shindell's calculations about TCRs is correct these confidence ranges would be heavily skewed to the high value side.  Furthermore, as the formal definition of ECS does not include any positive feedback from deep ocean, ice sheet and most carbon cycle feedbacks, the non-linear feedback illustrated by the Small et al 2014 temperature increase (say due to unexpectedly rapid rates of sea ice area, and summer/fall snow cover, reductions.

As the IPCC made extensive use of such rules of thumb to develop their carbon budgets, and as James Hansen yielded to political reality when he developed his 130 Gt CO2 carbon budget, I would be very careful in considering what such heavily caveated guidance really means.  Remember that Hansen originally wanted the CO2 atmospheric concentration to be rolled back to 350ppm in order to be safe, and the Small et al 2014 results seem to support such wisdom.

[AbruptSLR]

As I have stated that I view the NRC's recommendation to spend more research funds on geoengineering (including BECCS and other "Negative Emissions Technologies", NET) as an indication of how desperate our situation is, I thought that I should at least provide a little bit of background on NET so that we can consider whether such options are realistic or not.  In order to be as current as reasonable, I provide the following abstract on this topic for Pete Smith's talk about NET tomorrow at the AAAS conference, and some other relevant links below:

Pete Smith , University of Aberdeen, Aberdeen, Scotland
 
https://aaas.confex.com/aaas/2015/webprogram/Paper14398.html

Abstract: "Efforts to date to curb greenhouse gas (GHG) emissions have failed to prevent continued increases in emissions, with the rate of emissions growth higher during the 2000s than in the 1990s, and with GHG emissions reaching an all-time high of ~50GtCO2-eq. in 2010. This failure to reduce emissions over the 20+ years since the United Framework Convention on Climate Change (UNFCCC) came into being, now makes limiting increases in global warming to <2◦C (the threshold beyond which climate change is regarded as dangerous) extremely challenging. Since global GHG emissions are now much higher than they were when the UNFCCC was agreed, we are now facing the prospect of requiring “negative emissions technologies” (NETs: i.e., those that result in net removal of GHGs from the atmosphere), to reach atmospheric GHG concentrations consistent with a <2◦C target. NETs include: BioEnergy with Carbon Capture and Storage (BECCS), Direct Air Capture of CO¬2 using Sodium (or Calcium) Hydroxide (NaOH DAC) or monoethanolamine (MEA DAC), and atmospheric CO2 removal by accelerated weathering of magnesium oxide-bearing rocks (AW-MgO)
The potential of NETs has so far been examined only theoretically through Integrated Assessment Models (IAMs) which have shown considerable cost-competitive potential for GHG mitigation by NETs, even allowing atmospheric CO2 concentrations to be reduced below current levels. But the technology is controversial since CCS technologies have not yet been demonstrated at scale in major energy conversion applications, and for some options (such as BECCS) the large quantity of biomass required would have significant implications for land use and competition with non-energy uses of land such as food production.
There are risks associated with relying heavily on any technology that has adverse impacts on other aspects of planetary sustainability to achieve our climate goals. Though deep and rapid decarbonisation may yet allow us to meet the challenge of meeting the <2◦C climate goal through emissions reduction alone, this window of opportunity is rapidly closing, so there is likely to be some need for NETs such as BECCS in the future. An over-reliance on BECCS and other NETs in the future, if used as a means to allow continued use of fossil fuels in the present, is extremely risky since our ability to stabilise the climate at <2◦C declines as cumulative emissions increase. A failure of BECCS or other NETs to deliver expected mitigation in the future leaves us with no “Plan B”. “Plan A” must be to reduce GHG emissions aggressively."


See also:

http://newscenter.berkeley.edu/2015/02/09/electricity-from-biomass-with-carbon-capture-could-make-western-u-s-carbon-negative/

http://www.abdn.ac.uk/environment-food-security/profiles/pete.smith/

While such NET plans carry appropriate caveats, they contribute to the issue of scientists erring on the side of least drama by defusing the urgency of our situation by giving policy makers yet another reason to delay cutting emissions (because we can always just suck GHG out of the atmosphere anytime that flex out anthropogenic willpower).  However, we need to remember risks with BECCS include: (a) droughts can limit water availability to grow the plants; (b) floods can kill such bio-fuel crops; (c) early Spring weather can disrupt the germination period required to initiate many such crops; (d) competition with food for land will stress economics; (e) increasing global temperature will induce heat stress on such crops as well as the workers asked to harvest such crops; (f) increasing surface level ozone concentrations in the atmosphere can also stress such bio-fuel crops; (g) societal, financial and governmental stress/collapse can limit capital and other resources required to grow such crops, and (h) the decrease in albedo for many land surfaces could result in another positive feedback.  Furthermore: (a) the stress of developing such a large BECCS effort could accelerate the collapse of our economic systems and would likely accelerate fossil fuel use to develop the BECCS infrastructure; (b) the administration of such systems can be inefficient and corrupt; and (c) in the worst case flooded bio-fuel crops could generate methane emissions.

[sidd]

I am pessimistic on BECSS. Far better to reforest, and forget about bioenergy and biochar sequestration.

The proposal for accelerated weathering might go further. There are large olivine near surface deposits which might be milled and spread using solar power. I have cost seen figures of less than 10US$/ton CO2, but i don't necessarily believe them. There is another proposal to pump CO2 laden seawater into deep rock formations to create carbonates at depth, but i see no recent work.

It is quite clear that the scale of effort for effective CO2 capture from the air, and burial will have to be of the scale of the present fossil fuel mining industry worldwide.

sidd

[AbruptSLR]

While I like a lot of the things that sidd conveyed about NET options, I would like to point out that there already is another thread dealing with geoengineering at the following link:

http://forum.arctic-sea-ice.net/index.php/topic,363.0.html

Additionally, it seems easier/better to focus on reducing emissions because it is clear that the entity causing the emissions is responsible for paying for the fix; while it is much less clear to me who would pay for NET (or other types of geoengineering), as the likely next big source for increased GHG emissions will be the non-China developing world who do not have enough money to pay for NET (which implies that the first world would need to pay for it, which implies delayed, or non-existent, implementation).

[Lennart van der Linde]

as James Hansen yielded to political reality when he developed his 130 Gt CO2 carbon budget, I would be very careful in considering what such heavily caveated guidance really means. Remember that Hansen originally wanted the CO2 atmospheric concentration to be rolled back to 350ppm in order to be safe...

Hansen et al 2013 still aims at 350 ppm and shows in fig.5 what emissions reduction is necessary to reach 350 ppm at different points in the future, but without including the potential effect of 'slow' feedbacks:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081648

They say:
"A 6%/year decrease of fossil fuel emissions beginning in 2013, with 100 GtC reforestation, achieves a CO2 decline to 350 ppm near the end of this century (Fig. 5A). Cumulative fossil fuel emissions in this scenario are ~129 GtC from 2013 to 2050, with an additional 14 GtC by 2100. If our assumed land use changes occur a decade earlier, CO2 returns to 350 ppm several years earlier; however that has negligible effect on the maximum global temperature calculated below.

Delaying fossil fuel emission cuts until 2020 (with 2%/year emissions growth in 2012–2020) causes CO2 to remain above 350 ppm (with associated impacts on climate) until 2300 (Fig. 5B). If reductions are delayed until 2030 or 2050, CO2 remains above 350 ppm or 400 ppm, respectively, until well after 2500.

We conclude that it is urgent that large, long-term emission reductions begin soon. Even if a 6%/year reduction rate and 500 GtC are not achieved, it makes a huge difference when reductions begin. There is no practical justification for why emissions necessarily must even approach 1000 GtC."

And:
"Our calculated global warming as a function of CO2 amount is based on equilibrium climate sensitivity 3°C for doubled CO2. That is the central climate sensitivity estimate from climate models [1], and it is consistent with climate sensitivity inferred from Earth’s climate history [51]–[52]. However, this climate sensitivity includes only the effects of fast feedbacks of the climate system, such as water vapor, clouds, aerosols, and sea ice. Slow feedbacks, such as change of ice sheet area and climate-driven changes of greenhouse gases, are not included...

Excluding slow feedbacks was appropriate for simulations of the past century, because we know the ice sheets were stable then and our climate simulations used observed greenhouse gas amounts that included any contribution from slow feedbacks. However, we must include slow feedbacks in projections of warming for the 21st century and beyond. Slow feedbacks are important because they affect climate sensitivity and because their instigation is related to the danger of passing “points of no return”, beyond which irreversible consequences become inevitable, out of humanity’s control."

The longer we stay above 350 ppm, the higher the risk of 'slow' feedbacks taking over and of warming getting out of control. And figure 5 doesn't include those feedbacks yet, even though they may start to become substantial even before 2100.

[AbruptSLR]

wili,

While the attached figure (from the linked 2011 Skeptical Science article) only shows the decrease in extent of near surface permafrost, it still shows a rapid rate of loss:

http://www.skepticalscience.com/Permafrost-Final.html

Caption: "Modeled and projected loss of permafrost.  By 2100 permafrost will have thawed to a depth of 3 meters producing slope instability in mountain areas.  Courtesy UNEP/GRID-Arendal  Updated 10/12/11"

[AbruptSLR]

While most people who read this thread are very familiar with the linked 2014 article, but I would like to remind everyone that ignoring slow response feedback Michael Mann projects: (a) we will cross the 2 C threshold by 2036 assuming an ECS of 3C; or by (b) about 2019 assuming an ECS of 4.5C (see two attached figures).  This conservative estimate (non-conservative wrt public safety) certainly does not give policy makers much time to get serious about controlling climate change:

Michael Mann, (2014), " Earth Will Cross the Climate Danger Threshold by 2036",  Scientific American Volume 310, Issue 4

http://www.scientificamerican.com/article/earth-will-cross-the-climate-danger-threshold-by-2036/

[sidd]

As advised, I took the discussion to the geoengineering thread, thanx for the heads up.

sidd

[AbruptSLR]

as James Hansen yielded to political reality when he developed his 130 Gt CO2 carbon budget, I would be very careful in considering what such heavily caveated guidance really means. Remember that Hansen originally wanted the CO2 atmospheric concentration to be rolled back to 350ppm in order to be safe...

Hansen et al 2013 still aims at 350 ppm and shows in fig.5 what emissions reduction is necessary to reach 350 ppm at different points in the future, but without including the potential effect of 'slow' feedbacks:

Lennart,

Thanks for reminding me of Hansen et al's thinking on this matter.

Best,
ASLR

[AbruptSLR]

as James Hansen yielded to political reality when he developed his 130 Gt CO2 carbon budget, I would be very careful in considering what such heavily caveated guidance really means. Remember that Hansen originally wanted the CO2 atmospheric concentration to be rolled back to 350ppm in order to be safe...

Hansen et al 2013 still aims at 350 ppm and shows in fig.5 what emissions reduction is necessary to reach 350 ppm at different points in the future, but without including the potential effect of 'slow' feedbacks:

Lennart,

Thanks for reminding me of Hansen et al's thinking on this matter.

Best,
ASLR

The following extract (and associated first attached figure) from the IPCC WG3 AR5 SPM (2014) defines "Baseline" as GHG emission pathways that only consider the committed GHG reductions (i.e. the Cancun commitments) extant at the time of AR5 which gives a range of global mean surface temperature increases by 2100 of 25 to 7.8 C when considering both emission uncertainties and climate uncertainties.

http://www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_summary-for-policymakers.pdf

Extract: "Without additional efforts to reduce GHG emissions beyond those in place today, emissions growth is expected to persist driven by growth in global population and economic activities. Baseline scenarios, those without additional mitigation, result in global mean surface temperature increases in 2100 from 3.7 °C to 4.8 °C compared to pre-industrial levels (median values; the range is 2.5 °C to 7.8 °C when including climate uncertainty, see Table SPM.1) (high confidence)."

Unless COP21 (in Paris of 2015) can do better than Cancun commitments, we could well see a global mean surface temperature rise of 7.8 C.

The discussion in the linked carbon brief article reviews the different optional pathways forward (framed in the language of net-zero emissions, see the second, third and fourth attached images) that came out the February 2015 IPCC meetings in Geneva to be narrowed down for possible agreement at COP21 in Paris in Dec 2100.  Many of the Geneva options seem to follow the thinking of Hansen et al 2013 cited by Lennart (in Reply #640); and in an ideal world COP21 would develop a plan that would limit the peak temperature increase to 2 C and then use NET to reduce the 2100 temperature increase to 1.5 C.  However, currently the USA, China and India do not support any such "Net-Zero" emissions pathway, so until I see proof of progress by the policy makers it would seem that the best (assuming IPCC process determined values) anyone should expect is the IPCC WG3 AR5 Baseline pathway with a range of 2.5 to 7.8 C by 2100.

http://www.carbonbrief.org/blog/2015/02/briefing-the-15-options-for-net-zero-emissions-in-the-paris-climate-text/

See also
http://www.climateanalytics.org/publications/timetables-zero-emissions-and-2015-emissions-reductions-state-science-adp-agreement

[AbruptSLR]

As stated in my last post (Reply #645), the WG3 AR5 assessment of the range of the global mean surface temperature increase (relative to 1850 – 1900) for the baseline radiative forcing scenario in 2014 (essentially for the Cancun commitments) is 2.5 °C to 7.8 °C when including climate uncertainty, for what the IPCC calls a high confidence.  Furthermore, until I see some proof that economic growth of the non-China developing world (i.e. I do not care what the USA, the EU or China do) will not keep us on this anthropogenic radiative forcing pathway then I am not interested in talking about less aggressive pathways (given that LBJ warned 50-years ago of our current plight).  Also, I summarize the following selected reasons to believe that this assessment is likely "conservative" (i.e. errs on the side of least drama with regard to public safety):

(a) Drew Shindell (and others) demonstrated that the TCR values used in AR5 are too low (so the low end of the range is too low).
(b) AR5 did not include all of the "slow response" positive feedback mechanisms (such as: (1) permafrost degradation; (2) reductions [primarily due to deforestation] in Secondary Organic Aerosols (SOA); (3) WAIS partial collapse; etc.) that are likely to be activated before 2100 (so the high end of the range should be higher).
(c) The CESM – H model projections (the best publicly available climate simulation run to date) imply that the ECS may likely be in the 4.0 to 4.5 C range (as supported by Sherwood et al 2014) (so the low end of the range is too low).
(d) The full impact of the unrelenting build-up of GHG (480 ppm CO2e) has been masked recently by such temporary factors (that are all likely to be eliminated/diminished shortly) as: aerosols, cooling phases of the PDO & AMO, recent hiatus of strong El Nino events, recent spurt of plant growth, unusually high volcanic activity, etc.  One example of the significance of the coming unmasking is that as aerosols are cleaned-up polar amplification will likely increase from twice, to four-times, the global mean surface temperature increase.
(e) Cowtan & Way have demonstrated that the reported observed increases in global mean surface temperature increase are likely too low.
(f) Calibration of the feedback mechanisms used in all state-of-the-art ESM's (including CESM – H) are based on extrapolations of responses of Earth systems near equilibrium into non-stationary conditions that have never been observed before.   Thus if the scientists who have developed such state-of-the-art ESM projections have erred on the side of least drama then there could be some up-side surprises.
(g) There is always the risk that the aggregate of the Cancun commitments will not be achieved, and that anthropogenic radiative forcing could slip back up to the RCP 8.5 pathway (note that when the Kyoto Protocol limits pinched Japan & Canada they simply left the protocol, and it is very unlikely that COP21 in Paris will be legally enforceable).
(h) Focusing on global mean surface temperature increases could distract attention from fat/long tail risks; particularly if the actual right-tails are fatter, or longer, than for the PDFs cited by the IPCC AR5.

[AbruptSLR]

I would briefly like to point-out that my last two posts (Replies #645 & 646) focused on what I would consider to be "Black Swan" considerations that were left out of the IPCC AR5 projections.  As such considerations are not included in the guidance by the IPCC to policy makers, they are by definition "Black Swan" considerations because the decision makers are not considering them (much like the factors contributing to the 2008 financial melt-down).  Such Black Swan considerations can result in (a) right shifts in the hazard PDF; (b) increased variability in the hazard PDF and (c) right skewing of the hazard PDF, all as indicated by the first attached image from the IPCC.

Unfortunately, chaotic systems whether the stock market or the climate related Earth's Systems; are also at risk of reaching systemic resonance which can result in "Dragon King" events with a spike in the right-side of the tail of the PDF (see the second attached image, showing a PDF with a log-scale).  As the Earth Systems are full of examples of limited chaotic resonance such as strong El Nino (or La Nina) events in the ENSO cycle, or strong periods in the PDO and/or IPO cycles; it is reasonable to discuss the risks that continued strong anthropogenic radiative forcing (such as following either the Cancun commitments, or RCP 8.5) through 2050 could trigger one or more dragon king events that would then occur even if subsequent to 2050 policy makers (or the collapse of our economic engine) drastically reduce anthropogenic forcing.  This is a particular worry to me as both jai, and the CESM - H results, emphasize that due to thermal inertia (primarily from the ocean) the impacts of radiative forcing to 2050 can continue through 2100.  While I do not have time just now to add details, either later today, or tomorrow, I hope to post some replies addressing risks of such possible Dragon King events as: Albedo Flips; Marine Glacier collapse (both WAIS & GIS); and a possible flip to an Equable atmospheric pattern by (or near to) 2100.

[AbruptSLR]

Shock & Thaw: When the Sheet Hits the Fan, Part I

In the first two posts (Replies # 648 & 649) on plausible climate change related Dragon King events that could be triggered by 2050 (note that many Net-Zero emission proposals consider high rates of GHG emissions until 2050 followed by a rapid reduction in such emissions) following at least the AR5 WG3 Baseline anthropogenic forcing scenario, I focus only on the risk that by 2050 marine glaciers (and outlet glaciers in Greenland) could experience the Pliocene like conditions modelled by Pollard et al 2015 for Antarctica, that would then lead to rapid collapse of key marine glaciers (particularly those in the Amundsen Sea Embayment) associated with cliff failures and hydrofracturing (see earlier posts in this thread or numerous posts in the Antarctic folder).

First, I would like to note that currently no expert on this matter, that I am aware of, has publically stated that initiating such an Abrupt Sea Level Rise, ASLR, Dragon King event, by 2050, is likely.  Nevertheless, the paleo-record includes numerous examples of not only how rapidly the marine glaciers extant in the world today have collapsed in the past; but also how such rapid marine glacier collapse events have temporarily increased the effective climate sensitivity (see the following Climate Crocks link and the Antarctic folder):

http://climatecrocks.com/2014/05/05/new-research-east-antarctic-at-risk-of-unstoppable-melt/

http://www.nasa.gov/jpl/earth/antarctica-telecon20140512/

With these formalities out of the way, initiating such an ASLR Dragon King event by 2050 would require that the gateways (or ice calving fluxgates) of key marine (& outlet) glaciers such as PIG, Thwaites, Jakobshavn or possibly the Wilkes Basin (see the first attached image from Mengel & Levermann 2014); would become un-plugged (see the second and third images from Mengel & Levermann 2014, thus allowing the critical cliff failures and hydrofracturing (see the fourth attached image), which requires relatively deep water depths to occur (see Bassis et al 2013). However, the current ice models (see following references) are not sophisticated enough to project that these ice plugs will adequately degrade before roughly 2100 (thus raising the possibility that a good Net-Zero emissions plan could prevent this ASLR Dragon King event).  Therefore, I will discuss in my next post (Reply #649) why it is plausible that our current generation of glacier models are in adequate to identify this risk (that the ice plugs will be degraded by 2050); and that the ACME model may be adequate to quantify this risk when its mission is complete in 2025.

Mengel, M. & Levermann, A., (2014), "Ice plug prevents irreversible discharge from East Antarctica", Nature Climate Change, Volume: 4, Pages: 451–455, doi:10.1038/nclimate2226
http://www.nature.com/nclimate/journal/v4/n6/full/nclimate2226.html

Sun, S., Cornford, S. L., Liu, Y., & Moore, J. C. (2014). Dynamic response of Antarctic ice shelves to bedrock uncertainty. The Cryosphere Discuss., 8, 479-508, 2014

Bassis, J.N., and Jacobs,S., (2013), "Diverse calving patterns linked to glacier geometry", Nature Geoscience, 6, 833–836, doi:10.1038/ngeo1887.

Mouginot, J., Rignot, E., & Scheuchl, B. (2014). Sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013. Geophysical Research Letters, 41(5), 1576-1584.

Rignot, E., J. Mouginot, M. Morligem, H. Serossi, and B. Scheuchl, (2014), "Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011", Geophys. Res. Lett., doi: 10.1002/2014GL060140

Favier, L., Durand, G., Cornford, S. L., Gudmundsson, G. H., Gagliardini, O., Gillet-Chaulet, F., T. Zwinger, A. J. Payne, and A.M. Le Brocq. (2014). Retreat of Pine Island Glacier controlled by marine ice-sheet instability, Nature Climate Change, 4, 117–121 doi:10.1038/nclimate2094

Laurence C. Smith Vena W. Chu, Kang Yang, Colin J. Gleason, Lincoln H. Pitcher, Asa K. Rennermalm,Carl J. Legleiter, Alberto E. Behar, Brandon T. Overstreet, Samiah E. Moustafa, Marco Tedesco, Richard R. Forster, Adam L. LeWinter, David C. Finnegan, Yongwei Sheng, and James Balog, (2015), "Efficient meltwater drainage through supraglacial streams and rivers on the southwest Greenland ice sheet", PNAS, doi: 10.1073/pnas.1413024112

http://www.pnas.org/content/112/4/1001

[AbruptSLR]

Shock & Thaw: When the Sheet Hits the Fan, Part II
First, I point-out that the following thread on "Potential Collapse Scenarios for the WAIS" has additional support information:

http://forum.arctic-sea-ice.net/index.php/topic,31.300.html#lastPost

Second, I point-out that during the Pliocence conditions evaluated by Pollard et al 2015: (a) CO₂ levels were around 400ppm, and we are now around 400ppm of atmospheric CO₂, and after accounting for thermal inertia the impact of current GHGs will occur around 2050; and (b) global mean surface temperatures were about 2 to 3 C above pre-industrial levels; which following an AR5 WG3 Baseline forcing scenario should occur by or before 2050.

Third, extrapolating the observed sub-ice-shelf melt rates for Antarctica shown in the first attached image from Rignot et al 2013, indicates that all key ice shelves in the key Amundsen Sea Embayment, ASE, should have collapsed by 2050; which, should leave the associated key marine glaciers subject to the hydro-thermodynamic feedback described by both Van der Veen et al (2011) for the Jakobshavn Glacier (see the second attached image, and note that the third attached image shows that the terminus for the Jakobshavn calving face is on-track to sustain a rapid retreat circa 2020) and more recently by Dunse et al (2015).

Fourth, extending the recent WAIS surface temperature increase trend-line shown in the fourth attached image from Orsi et al 2012; indicates that surface melting of the ice in the ASE marine glaciers should become increasingly more frequent (also due to the projected increasing frequency of strong El Nino events that teleconnect atmospheric energy from the Tropical Pacific to the WAIS); which should increase the frequency of the hydro-thermodynamic feedback mechanism cited in the third point, to the point that the gateway ice plugs may collapse by 2050.

Fifth, once the gateway ice plugs have collapsed the icebergs resulting from the subsequent cliff failure and hydrofracturing mechanisms can rapidly float out through the open gateways.


E. Rignot, S. Jacobs, J. Mouginot & B. Scheuchl, (June 2013), "Ice Shelf Melting Around Antarctica" Science DOI: 10.1126/science.1235798

C.J. Van der Veen, J.C. PLUMMER & L.A. STEARNS, (2011), "Controls on the recent speed-up of Jakobshavn Isbræ, West Greenland", Journal of Glaciology, Vol. 57, No. 204

http://www.igsoc.org:8080/journal/57/204/j10J070.pdf

ABSTRACT: "Jakobshavn Isbræ, West Greenland, underwent a large, rapid and not well understood change in flow dynamics in 1998, leading to a doubling of its ice discharge rates. We calculate the width-averaged forces controlling flow of Jakobshavn Isbræ in 1995, 2000 and 2005 to elucidate processes responsible for this change in flow speed. In contrast to earlier suggestions, we conclude that the observed acceleration was not caused by the loss of back-stress due to weakening and subsequent break-up of the floating ice tongue alone. Gradients in longitudinal stress are small at all times considered (~3% of the driving stress) and basal and lateral drag provide resistance to flow. Over the 10 year period considered, the average driving stress increased by 20 kPa, which was balanced by a comparable increase in lateral drag. We surmise that the velocity changes resulted from weakening of the ice in the lateral shear margins and perhaps a change in properties at the bed. Possible mechanisms for weakening of ice in the lateral shear margins include cryo-hydrologic warming of subsurface ice in the ablation zone and hydraulic weakening due to higher water content of ice in the shear margins."

See also:

http://www.the-cryosphere.net/8/209/2014/tc-8-209-2014.pdf


Dunse, T., Schellenberger, T., Hagen, J. O., Kääb, A., Schuler, T. V., and Reijmer, C. H.: Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt, The Cryosphere, 9, 197-215, doi:10.5194/tc-9-197-2015, 2015.

http://www.the-cryosphere.net/9/197/2015/tc-9-197-2015.html

Orsi, A.J., Cornuelle, B.D., and Severinghaus, J.P., (2012), "Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide", Geophysical Research Letters, vol. 39.

While this discussion is somewhat abbreviated (see the Antarctic fold more other details), it at least indicates the plausibility of the initiation of the collapse phase of key WAIS marine glaciers (and at least the Jakobshavn outlet glacier) by 2050.  Furthermore, as stated previously the initiation of such an ASLR Dragon King event by 2050 could: (a) accelerate the rate of Arctic Sea Ice loss by driving warm Pacific water through the Bering Strait into the Arctic Ocean; (b) by inducing accelerated frequencies of global earthquakes and volcanic activity, due to the rapid rate of sea level rise; and (c) contribute to an acceleration of Antarctic Amplification.