Conservative Scientists & its Consequences

[Shared Humanity]

I come to this site frequently and find it enlightening. I rarely comment on many of these threads because my knowledge of the science is limited. This is the type of thread on which I rarely contribute. The discussion here is fascinating. I am particularly intrigued by the concept of Earth System Sensitivity (ESS) that has been raised and feel that I now have a contribution to make.

All systems have some very basic components and ways of behaving. I will not go into system behavior in great detail here. If you want to dive into an easily understood book regarding systems, I would highly recommend "Thinking in Systems" by Donella H. Meadows.

Systems are composed of stocks, flows and feedback loops. Feedbacks, as discussed here, can be fast or slow. They can also be reinforcing or stabilizing. Reinforcing feedbacks result in exponential growth and runaway loops. I love systems modeling and analysis. I love it because it allows us  to get at the heart of a problem and strip away the noise.

Slow feedbacks are one of the most interesting components of any system. They always have a surprising impact on system behavior precisely because they are slow. This slowness makes it difficult to identify these loops until the impacts are felt. It also makes it difficult to quantify the  impact on system behavior.

I have attached a simple model of the Earth System. Models can be quite complex but simple models often are the most useful as they allow us to reach inescapable conclusions quickly and easily. All models are wrong. Some models are useful.

I assume everyone who is commenting on this thread agrees that the feedback loops in this system model are reinforcing. (I am not interested in talking to any who don't believe this.) Looking at this model scares the bejeebers out of me.

Questions for which I have no answer (I will give my inexpert opinion to the first and this opinion has been influenced by the discussions on this wonderful website.) These questions are being discussed here and, depending on the answers, are the source of my fear:

1. Do we know all of the slow feedback loops? My answer is no and it is no precisely because these feedbacks are slow.

2. Have we begun to see an impact on earth temperature stocks from any of these slow feedback loops? I have no idea but, if we are seeing them, we are already in a system that is exhibiting runaway behavior. Since the feedback loops are slow this runaway behavior will continue for a long time.

3. How quickly will these slow feedback loops impact the level of "earth temperature stocks? Put in a different manner, what is the doubling rate of temperature increases? Again, I have no idea.

Please keep in mind, this last question needs to be asked because systems with reinforcing loops ALWAYS result in exponential growth!

[Shared Humanity]

A quick comment...

I believe most comments about whether a contributor to this discussion is a troll or not are unnecessary and diminish the site. However, given that all of us believe the feedback loops are net reinforcing, it is relatively easy to categorize comments about rainfall in Australia or temperature increases in the U.S. as noise and irrelevant and should be ignored as they do not enlighten or contribute to the discussion.

I would like to point out that these kinds of contributions would be relevant on other threads on this site.

Perhaps this one....

http://forum.arctic-sea-ice.net/index.php/topic,317.0.html

[AbruptSLR]

S.H.,

I enjoyed your post Reply #550 very much.  Your three questions are all critical and your answers are as good as anyone's.  Note that I think that AR5 is just one stop on the Roadmap towards sufficiently understanding climate change in order to be able to reasonably answer such questions.  Additional quick thoughts that I have on this matter include the following:

(a) Before Earth Systems Models, ESM, were adequately developed many researchers (including James Hansen) leaned heavily on documenting and then trying to replicate the paleo-record; which was very appropriate at the time, but the paleo-record came from an Earth System that was never too far out of equilibrium at any one time.  Therefore, paleo definitions of "slow" and "fast" feedback mechanisms become less and less appropriate to use for our modern condition the further our condition departs from equilibrium.

(b) Science is inherently reductionist, and uses both Frequentist, and Bayesianist, approaches to both break-down the non-stationary Earth Systems/data and then to re-construct it into models (with various simulation runs), but the "Devil is in the detail" and thus science must use an iterative approach to self-correct errors in its earlier models & data.

As I have stated before, my best hope of achieving anything like reasonably reliable answers to your questions (and other similar questions) is to use an approach like that currently being implemented by the DOE's ACME program (& ESM) described by the free access pdf at the following link and the following associated images and extract.

In summary, I agree with your concerns on this topic and I do not think that the DOE would be spending hundreds of millions of dollars on the ACME project unless your concerns had merit.

Best,
ASLR

http://climatemodeling.science.energy.gov/sites/default/files/publications/acme-project-strategy-plan.pdf

Extract: "ACME will achieve this goal through four intersecting project elements:
1. a series of prediction and simulation experiments addressing scientific questions and mission needs;
2. a well-documented and tested, continuously advancing, evolving, and improving system of model codes that comprise the ACME Earth system model;
3. the ability to use effectively leading (and “bleeding”) edge computational facilities soon after their deployment at DOE national laboratories; and
4. an infrastructure to support code development, hypothesis testing, simulation execution, and analysis of results.

Figure 1 depicts the ACME Project Roadmap, showing the relationships among the first three major project elements: the simulations, the modeling system to perform those simulations, and the machines on which they will be executed. Unlike the other three elements that have distinct but overlapping phases, the fourth element, the infrastructure, will evolve continuously based on the requirements imposed by project needs.

…

Could a dynamical instability in the Antarctic Ice Sheet be triggered within the next 40 years? "

[AbruptSLR]

Interestingly, the abstract from Steven's referenced article says the following.

http://www.nature.com/nature/journal/v518/n7537/full/nature14145.html

it seems that they attribute a significant ECS value to the gradual loss of surface ice in transition from partial and inter stadial to equitable climate regimes.

We find that Earth’s climate sensitivity to CO2-based radiative forcing (Earth system sensitivity) was half as strong during the warm Pliocene as during the cold late Pleistocene epoch (0.8 to 0.01 million years ago).

and

predictions of equilibrium climate sensitivity (excluding long-term ice-albedo feedbacks) for our Pliocene-like future (with CO2 levels up to maximum Pliocene levels of 450 parts per million) are well described by the currently accepted range of an increase of 1.5 K to 4.5 K per doubling of CO2.

jai,

While I know that you are very familiar with Hansen's work, others tend to forget figures like the attached from Hansen & Sato 2012; which combines the currently relatively constant "fast feedbacks" together with "Surface Albedo" to give an approximate idea of the types of risks that society is currently facing if we push the Earth Systems too far out of equilibrium with aggressive anthropogenic radiative forcing.

Best,
ASLR

[Shared Humanity]

Thanks AbruptSLR. I read all of your posts and understand only portions.

[AbruptSLR]

Thanks AbruptSLR. I read all of your posts and understand only portions.

S.H.
While this thread is focused on whether scientific guidance on climate change, such as that given in IPCC's Assessment Report 5, is too conservative (ie erring on the side of least drama while exposing society to excessive risk); there is no need to everyone to understand all of the scientific nuances.  What really counts is that people recognize that climate change is threatening the things that we value and that fighting climate change is worth the effort.  While climate change threatens many different things (the economy, the environment, food, water, health, etc.), the thing that disturbs me the most is that we are putting our current, & future, generations of youth into an untenable position, and that this is already occurring as indicated by the linked article (and extract):

http://in.reuters.com/article/2015/02/05/india-children-climatechange-idINKBN0L92AE20150205

Extract: "Disasters resulting from climate change are pushing poor Indian families into poverty so deep that they are lured by traffickers into selling their children into bonded labour or prostitution, Nobel Peace Laureate Kailash Satyarthi said on Thursday.
"I have witnessed many incidents where the children became the worst victims of environmental disasters caused by climate change and these kind of things," Satyarthi told Reuters TV on the sidelines of a conference on climate change.
"It has resulted in displacement of the parents, and eventually the children are compelled to become child labourers or even child prostitutes or child slaves because they lose their traditional livelihood.""

I have heard some people say that even without climate change impacts, people, and children, will suffer anyway.  Nevertheless, we can each choose to make things better, or to make things worse; and in my book meaningful climate change will make everything worse (including child slavery), and the sooner that we demand that public representatives take effective action (including: a progressive carbon fee & dividend plan, family planning, etc.); then we can count ourselves as part of the problem.
Best,
ASLR

[AbruptSLR]

 Additional discussion of problems with the IPCC – AR5 carbon budget:
- The negative feedback associated with the high anthropogenic aerosols most significantly over China, India and Nigeria induce a meaningful reduction in the current global mean temperature increase; however, this negative aerosol feedback does almost nothing to reduce the risk of the non-linear activation of the tropical atmospheric deep convective mixing positive feedback that is probably the greatest risk that ECS could grow to 4 to 4.5 C in the coming couple of decades as tropical warming continues to accelerate.  Thus while the IPCC – AR5 carbon budget assumes that the effective equivalent CO₂ forcing in 2011 was close to 425 ppm, as far as activation of the critical deep convective mixing positive feedback is concerned it may as well be 480 ppm.
- The preliminary CO₂ emissions for 2014 were about 2.6ppm which indicates that anthropogenic GHG emissions are presently accelerating, and are not decelerating as RCP 2.6 assumes.
- As the PDO has apparently entered its positive phase we can expect the oceans to absorb less than its normal amount of heat uptake; which means that for the next 17 to 25 years mean global temperature increase will likely increase at a faster rate than normal, and per Michael Mann (per his 2014 Scientific American article) we should pass the 2 C mean global temperature increase before 2035.
- I also the attached Scientific American graphic about a carbon budget bathtub concept to help those who would like to better visualize the different carbon sources and sinks (w.r.t. carbon budget limits).

[AbruptSLR]

The attached image shows probabilities for three families of scenarios for global-mean temperature change where "Reference" is similar to RCP 8.5, or SRES A1FI, "Developing Country Delay" is similar to SRES A1B but more forceful than RCP 6, and "Full Participation" (2009 Kyoto Protocol participation by all countries) is similar to SRES B1 but more forceful than RCP 2.6.  I present this image because it emphasizes the importance of the developing world in controlling GHG emissions, and with China now exporting more capital to other developing countries than it is receiving, we can expect countries like Nigeria, Indonesia, and India to increase rather than decrease GHG emissions in the next 20 to 50 year timeframe.

[AbruptSLR]

To support the idea that GHG emissions are not likely to drop anytime soon, the linked article (& associated plot) shows that global GDP should grow at a rate of 3.6% (up from 3.3% in 2014), boosted by lower oil prices and strong growth in developing countries (see dark green on map for Nigeria, Indonesia, India, China, and note that a great many African countries shown in grey would also be dark green if their data were reported).  This indicates that we will continue consuming any remaining part of a carbon budget faster than the IPCC – AR5 anticipated:
http://www.businessinsider.com/deutsche-bank-gdp-growth-map-2015-1

Extract: "Deutsche Bank is predicting global GDP growth of 3.6% in 2015, up from 3.3% in 2014. A big part of that jump comes from the bank's projection that US growth will accelerate to 3.7% this year, powered by ongoing accommodation by the Fed, stronger consumer and business spending, a housing market finally returning to normal, and the presumed boost to consumers from lower oil prices."

[dorlomin]

Let me show people how Steve McIntyres climate auditing works.
He picks a group he does not like.

by the IPCC process)

He then takes the statistical approach they used.

Frequentists

He then produces a bioler plate critque of the potential flaws in that technique (all techniques have them.)

can (and do) construct investigations anyway that they want and then do a frequency count of the out-coming and then declare that their frequency count represents the true probability;

Then add some scolding hand waving....

which is the truth behind the common saying: "There are lies, damn lies and statistics".  In other words if the investigation is not well-constructed its frequency count will not represent the true probability (ie "Garbage in, Garbage out").

And et viola you now have debunked a paper or report with actually having looked at it in anything but the flimsiest details.

And off course this all happens to rapturous applause by an audience that generally does not understand what he is saying.

This thread is simply chock full of lazy conspiracy theories and handwaving. Backed up by flabby cut and pastes that seem to meander along without actually saying anything relevant.

[viddaloo]

And et viola you now have debunked a paper or report with actually having looked at it in anything but the flimsiest details.

... says the guy who didn't even look twice at his own summary sentence to see if it compiled semantically. Laziness. Mental obesity. So sad to see in a good thread.

[Neven]

This thread is simply chock full of lazy conspiracy theories and handwaving. Backed up by flabby cut and pastes that seem to meander along without actually saying anything relevant.

And you try to increase the quality how? 

Insulting people by comparing them to Iago McIntyre is definitely not the way to go. Next you'll be comparing me to Anthony Watts. But you know, AbruptSLR nor I are paid to do this, and speaking for myself, I don't have very strong ideological motives (or at least, am not aware of them). I just don't like risks, and I don't like the idea that what I'm doing might hurt other people.

And the argument can be made, and is made by AbruptSLR and others, that the IPCC is erring on the side of least drama when it comes to several issues. That doesn't necessarily mean the argument is right, but it can be made. So it's definitely not some conspiracy whacko theory. I wish it were. 

No need to involve Iago McIntyre. AbruptSLR isn't trying to poison anyone.

[crandles]

3. How quickly will these slow feedback loops impact the level of "earth temperature stocks? Put in a different manner, what is the doubling rate of temperature increases? Again, I have no idea.

Please keep in mind, this last question needs to be asked because systems with reinforcing loops ALWAYS result in exponential growth!

But do you accept that Earth hasn't so far gone into a Venus like run away?

If you do accept this, do you agree that this is strong evidence that ultimately outward radiation rising at 4th power of temperature is likely a stronger effect than the positive feedback loops and this tends to keep temperatures in a relatively stable range?

This doesn't mean we cannot get to a warmer climate than Eocene so CC is a problem. i.e. The 'relatively stable range' is still much larger than we would want to experience.

However, I think the above does put a different complexion on the situation than a 'we should be terrified of the slow feedbacks' that seems to be what your post is arguing.

I assume everyone who is commenting on this thread agrees that the feedback loops in this system model are reinforcing. (I am not interested in talking to any who don't believe this.)

Am I allowed a 'depends on the timeframe' answer?

Over hundreds of millions of years, I think we know the rock weathering feedback is stabilising. Ie warmer temperatures -> more rock weathering -> more carbon sequestration in sedimentary rocks -> greenhouse gas cooling effect = stabilising feedback.

(Is it just a co-incidence that this effect seems to help life survive and flourish? Or is there a lifeforms that don't act in biodiversity's favour tend to get eliminated also involved here?)

Just because the feedback is slow does not mean we do not know about this feedback. I agree there is likely to be other feedbacks we are not aware of. I would however suggest that if we don't know about them the effects are more likely to be weak and slow. Therefore error from ignoring them is likely to be small. Far enough in the future, the effect could be large but that isn't a reason to ignore short term predictions of what will happen.


Certainly, over years, decades, centuries, millennia, and ignoring the outgoing radiation increasing with fourth power of temperature, I think the feedbacks are positive.

These are the feedbacks that are most relevant to human timescales and we cannot hope for rock weathering feedback to save the current situation.

Regarding your question 2, I think what we are seeing so far is almost all a result of the forcing we are applying. Vast majority of the remainder is from fast feedback. This leaves very little if any effects from slow feedbacks. (Pedantic point: stocks are of heat energy, temperature is a measure of heat density.)

[dorlomin]

Insulting people by comparing them to Iago McIntyre is definitely not the way to go.

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

I don't have very strong ideological motives (or at least, am not aware of them)

Being right when mainstream science is itself wrong is a motivation.

the IPCC is erring on the side of least drama when it comes to several issues.

This is what they have been set up to do. 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.

[Michael Hauber]

1. Do we know all of the slow feedback loops? My answer is no and it is no precisely because these feedbacks are slow.

We have evidence of feedbacks that occur up to century time frames, and up to half a doubling of Co2, which is what we have had so far.  We also have incomplete evidence of all the slow feedback loops that have occurred in the paleo-climate record.  We can also attempt to get some measure on slow feedback loops by isolation of a specific process.  As an example while ice sheet albedo is slow enough that it has done nothing measurable to the amount of warming, we can measure how many cubic kilometres of ice have fallen off the sides of Antarctica and Greenland, and attempt to extrapolate.

An interesting aspect of an exponential growth path for emissions, is that the proportion of emissions that have occurred within the last X years will stay the same as long as we maintain exponential growth.  So if there was some way we could actually maintain RCP8.5 for 100 years without negative impacts of climate change slowing down growth, or without humanity deciding to slow down then in 2100 we would be in the same position as today waiting for slow feedback effects to kick in.  It is only when we start to slow emissions from an exponential growth trajectory that the fraction of emissions from say greater than 50 years ago can increase and we will see first hand the impacts of slow feedback.

Please keep in mind, this last question needs to be asked because systems with reinforcing loops ALWAYS result in exponential growth!

A reinforcing loop can either diverge (1 + 2 + 4 + , which results in explosive exponential growth (limited by a source for the loop - e.g. if water vapour was in this class it would be limited by the amount of water in the oceans and would stop when the oceans boil dry).  A typical example is a fire or explosion which uses up all the fuel.

Or the loop converges (1 + 0.5 + 0.25 + 0.125), in which case the process starts faster, and slows down rapidly to approach a limit.  (e.g. the above series will never get past 2).  A good example is water vapour feedback, which is  a reinforcing loop, but has so far failed to go runaway and boil away all our oceans.

[GeoffBeacon]

Dolomin

We are asking people to take a huge change in their lives, a huge change in the economic foundation of their society.

The "current economic foundation" is making "our society" more unequal and the people less happy. There is a good TED talk by Richard Wilkinson, http://www.ted.com/talks/richard_wilkinson.

A huge change could make us happier.

I believe we are taking huge risks with climate, which would be helped by a high carbon tax (or carbon pollution fine). But climate change aside, this would make life so much more peaceful. We would breathe less car filth, have economies that were more local and stop beef and lamb production taking agricultural land to price the poor out of the world market for food. No climate science necessary to see that.

Collecting the carbon pollution fines could enable us to cut labour taxes to create jobs and pay for necessary nation expenditure. Climate change is the worst threat we are facing but there are plenty of others, like war and disease that will need great expenditure.

Are the people you are worried about the affluent polluters that have been exploiting the poor of the world and leaving oil-fueled wars in their wake.  The greed for oil has paid for the strife that the world is facing.

[Michael Hauber]

RCP 8.5 and RCP 2.6 would constructed to represent the 90th and the 10th percentile of the post-SRES literature

Is that your evidence that the RCPs were created using a 'frequentist' approach? 

While obtaining a 'probability distribution function' from a literature review might be considered 'frequentist', I don't think that is what the typical distinction of frequentist vs Bayesian usually is about (how would a Bayesian approach possibly do anything different?).  It certainly seems a valid way of obtaining a reasonable spread.  Is there any way you can propose a better process, and in what way does taking the 10th and 90th percentile of currently available literature bias the outcome? 

[Michael Hauber]

While some deny that the AR5 officially discusses a carbon budget to stay below 2 C, the following link leads to an official IPCC cite discussing the carbon budget:

http://www.ipcc.ch/pdf/presentations/WMO_EC/2%20plattner14wmo_exec_council_prelim.pdf

See also:
http://www.ipcc.ch/news_and_events/outreach.shtml

More specifically, Reto Knutti is one of the lead authors for the AR5 WG1 report and the ClimateChange2013 website is an official IPCC website, there can be no doubt that the linked R. Knutti PowerPoint represents official IPCC guidance regarding a carbon budget:

http://www.climatechange2013.org/images/uploads/7_knutti13sed2_v1.pdf

See also:
http://www.climatechange2013.org/

Authors of WGI report:
 Lisa V. Alexander (Australia), Simon K. Allen (Switzerland/New Zealand), Nathaniel L. Bindoff (Australia), François-Marie Bréon (France), John A. Church (Australia), Ulrich Cubasch (Germany), Seita Emori (Japan), Piers Forster (UK), Pierre Friedlingstein (UK/Belgium), Nathan Gillett (Canada), Jonathan M. Gregory (UK), Dennis L. Hartmann (USA), Eystein Jansen (Norway), Ben Kirtman (USA), Reto Knutti (Switzerland), Krishna Kumar Kanikicharla (India), Peter Lemke (Germany), Jochem Marotzke (Germany), Valérie Masson-Delmotte (France), Gerald A. Meehl (USA), Igor I. Mokhov (Russian Federation), Shilong Piao (China), Gian-Kasper Plattner (Switzerland), Qin Dahe (China), Venkatachalam Ramaswamy (USA), David Randall (USA), Monika Rhein (Germany), Maisa Rojas (Chile), Christopher Sabine (USA), Drew Shindell (USA), Thomas F. Stocker (Switzerland), Lynne D. Talley (USA), David G. Vaughan (UK), Shang- Ping Xie (USA)

The carbon budget is not contained in the official IPCC reports.  It is included in one presentation with an IPCC association, and with no reference of where the budget came from or how it was calculated.  Doesn't look like what I'd call an official IPCC position, and I can't see how it would have gone through the same process as the official IPCC reports of being endorsed line by line by an argumentative and nit-picky panel.

[AbruptSLR]

While we are certainly not headed for Venus-type climate conditions for the next billion years, nevertheless, that does not mean that because the CMIP5 projections used in AR5 did not identify abrupt climate change in the next century or two, that such abrupt climate change cannot happen by 2100. 

Indeed, as pointed out in the linked reference the generation of model projections available before the AR5 submittal cut-off date could not even simulate the documented abrupt climate changes in the paleo-record.  While the somewhat advanced "EC Earth" ESM used in the Drijfhout et al (2013) study demonstrated that such abrupt climate changes can occur spontaneously (without any external forcing) due to natural variability.  This indicates that there are very good reasons to build even more advanced ESMs like ACME, in order to better define the risks associated with potential abrupt climate change this century (particularly for BAU cases).


Sybren Drijfhout, Emily Gleeson, Henk A. Dijkstra & Valerie Livina, (2013), "Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation, PNAS, vol. 110 no. 49, pp. 19713–19718, doi: 10.1073/pnas.1304912110

http://www.pnas.org/content/110/49/19713.abstract


Abstract: "Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change."

See also:
http://phys.org/news/2013-11-climate-capable-simulating-abrupt.html

Extract: "Clues from the geological record have allowed scientists to detect abrupt transitions between different climate states, but until now they have not been able to recreate them in computer models of past climates."

[Michael Hauber]

I believe most comments about whether a contributor to this discussion is a troll or not are unnecessary and diminish the site. However, given that all of us believe the feedback loops are net reinforcing, it is relatively easy to categorize comments about rainfall in Australia or temperature increases in the U.S. as noise and irrelevant and should be ignored as they do not enlighten or contribute to the discussion.

http://forum.arctic-sea-ice.net/index.php/topic,317.0.html

The point is that the claim is made that the IPCC are systematically underestimating climate impacts.  These support my argument that the IPCC are competent but imperfect so will overestimate some things and underestimate others.  While these impacts may be minor in the global scheme of things, they prove that the IPCC are not systematically overestimating climate impacts.  Unless you want to propose a conspiracy theory where the IPCC overestimate a few minor impacts to appear legitimate while underestimating all the major impacts that matter....

[AbruptSLR]

The first attached image is from the United Nations' WCRP (World Climate Research Programme) Task Group on Sea Level Variability and Change (2009), shows the TAR (See the second attached image with the caption below) and AR4 SLR projection ranges vs the historical record.  This shows that the historical record was consistently following the upper edge of the 95% CL range of the model projections, and consequently in AR5 the IPCC increased the model projections by about 50% so that the historical record would be closer to the median of the projections.  Clearly IPCC projections are subject to major changes in order to better match observations (per the scientific method).

http://www.ipcc.ch/ipccreports/tar/vol4/index.php?idp=104

Caption: "Global average sea level rise 1990 to 2100 for the SRES scenarios. Thermal expansion and land ice changes were calculated using a simple climate model calibrated separately for each of seven AOGCMs, and contributions from changes in permafrost, the effect of sediment deposition and the long-term adjustment of the ice sheets to past climate change were added. Each of the six lines appearing in the key is the average of AOGCMs for one of the six illustrative scenarios. The region in dark shading shows the range of the average of AOGCMs for all thirty five SRES scenarios. The region in light shading shows the range of all AOGCMs for all thirty five scenarios. The region delimited by the outermost lines shows the range of all AOGCMs and scenarios including uncertainty in land-ice changes, permafrost changes and sediment deposition. Note that this range does not allow for uncertainty relating to ice-dynamic changes in the West Antarctic ice sheet."

[jai mitchell]

But do you accept that Earth hasn't so far gone into a Venus like run away?

If you do accept this, do you agree that this is strong evidence that ultimately outward radiation rising at 4th power of temperature is likely a stronger effect than the positive feedback loops and this tends to keep temperatures in a relatively stable range?

This is an interesting tack.  I wonder though, do you realize that the measurement of the Earth's energy imbalance, most clearly evidenced by the NOAA plot of Ocean Heat Content is growing at an ever increasing rate?

This means that, as the earth has been warming, the amount of heat energy that is being radiated away to space has not kept pace with the increase of radiative forcing from greenhouse gasses and associated fast feedback mechanisms.

While our emissions continue to increase, the 'equilibrium warming date" is grown at about 1/2 pace.  In other words, our equivalent warming today of (around) .8C is the near term equilibrium warming (absent slow feedbacks) from about 1975.  And next year it will be 2016 but our warming regime will be operative of 1975.5  and so on.

So as our radiative forcing from GHG emissions continues to outpace the rate of surface temperature warming (it is called, "thermal inertia") this will produce an increased potential for catastrophic warming.  Like a coiled spring. 

In addition, it should be noted that current solar cycle activity is as low as it has been in over 100 years and significant south-east Asian aerosol forcing is working to reduce the current radiative forcing profile, in a potentially significant way.  This aerosol forcing activity is short-lived and as these emissions are reduced, either by the installation of scurbbers or by the reduction in coal consumption, the compound effect will be paramount.

This is why the long-term warming trend looks like this:  (when the radiative forcing function from greenhouse gas accumulation is actually logarithmic in nature)

[wili]

Nicely summarized, jai.

[Neven]

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

No one here is claiming that it is a giant conspiracy, because a conspiracy involves a group of people consciously and untransparently working towards a certain goal. The claim here is that the IPCC underestimates certain aspects of AGW because of the fear of type I errors and the natural conservatism of scientists. Again, this argument can be made IMO.

Being right when mainstream science is itself wrong is a motivation.

Perhaps, but it's not an ideological motivation, and so you can't go and compare people with Iago McIntyre. I mean, based on your two last posts I could go and claim you're a Wattsbot trying to derail the conversation with strawmen and fake concern. Would you think that's fair?

This is what they have been set up to do. 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.

You will never get certainty, that's not what this is about. It's about risk management, and so we need the IPCC to not underestimate things like Arctic sea ice loss, permafrost melting and sea level rise.

And AGW is just one of many reasons to make a huge change in the way the economic system is currently set up, the sooner, the better.

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.

Nothing would make me more happy to see the neoclassical economic theory of infinite growth correct, to gorge in consumer culture and thus improving the lives of billions of people. I'm already living like a king, and if I were sure that there are no risks posed by AGW or any other possible limit to growth, or at least that they have a decent chance of being solved because of changes underway, I would not have much of a personal desire on the societal level.

Are you sure you are the dorlomin I've known from the Guardian and various climate blogs?

[Lennart van der Linde]

The carbon budget is not contained in the official IPCC reports.

Are you sure?

IPCC AR5 Synthesis Report says, with references to WG1 and WG3:
"limiting total human-induced warming (accounting for both CO2 and other human influences on climate) to less than 2°C relative to the period 1861-1880 with a probability of >66% would require total CO2 emissions from all anthropogenic sources since 1870 to be limited to about 2900 GtCO2 when accounting for non-CO2 forcing as in the RCP2.6 scenario, with a range of 2550–3150 GtCO2 arising from variations in non-CO2 climate drivers across the scenarios considered by WGIII (Table 2.2). About 1900 [1650 to 2150] GtCO2 were emitted by 2011, leaving about 1000 GtCO2 to be consistent with this temperature goal. Estimated total fossil carbon reserves exceed this remaining amount by a factor of 4 to 7, with resources much larger still. {WGI SPM E.8, WGI 12.5.4, Figure 12.45; WGI TS TFE.8, Figure 1, TS.SM.10, WG III Tables SPM.1, 6.3 and 7.2}"

Looks like a carbon budget to me.

[Lennart van der Linde]

IPCC AR5 WG1 SPM says:

Limiting the warming caused by anthropogenic CO2 emissions alone with a probability of >33%, >50%, and >66% to less than 2°C since the period 1861–188022, will require cumulative CO2 emissions from all anthropogenic sources to stay between 0 and about 1570 GtC (5760 GtCO2), 0 and about 1210 GtC (4440 GtCO2), and 0 and about 1000 GtC (3670 GtCO2) since that period, respectively. These upper amounts are reduced to about 900 GtC (3300 GtCO2), 820 GtC (3010 GtCO2), and 790 GtC (2900 GtCO2), respectively, when accounting for non-CO2 forcings as in RCP2.6. An amount of 515 [445 to 585] GtC (1890 [1630 to 2150] GtCO2), was already emitted by 2011. {12.5}

A lower warming target, or a higher likelihood of remaining below a specific warming target, will require lower cumulative CO2  emissions. Accounting for warming effects of increases in non-CO2 greenhouse gases, reductions in aerosols, or the release of greenhouse gases from permafrost will also lower the cumulative CO2 emissions for a specific warming target (see Figure SPM.10). {12.5}

WG1 12.5.4 adds:

Combining the average back-calculated fossil fuel carbon emissions for RCP2.6 between 2012 and 2100 (270 PgC) with the average historical estimate of 515 PgC gives a total of 785 PgC, i.e., 790 PgC when rounded to 10 PgC. As the 785 PgC estimate excludes an explicit assessment of future land-use change emissions, the 790 PgC value also remains a conservative estimate consistent with the overall likelihood assessment… The concept of a fixed cumulative CO2 budget holds not just for 2°C, but for any temperature level explored with models so far (up to about 5°C; see Figures 12.44 to 12.46), with higher temperature levels implying larger budgets.

[Lennart van der Linde]

WG1 6.4.3.4 adds:

none of the models participating in C4MIP or CMIP5 included explicit representation of permafrost soil carbon decomposition in response to future warming. Including permafrost carbon processes into an ESM may change the sign of the high northern latitude carbon cycle response to warming from a sink to a source (Koven et al., 2011). Overall, there is high confidence that reductions in permafrost extent due to warming will cause thawing of some currently frozen carbon. However, there is low confidence on the magnitude of carbon losses through CO2 and CH4 emissions to the atmosphere. The magnitude of CO2 and CH4 emissions to the atmosphere is assessed to range from 50 to 250 PgC between 2000 and 2100 for RCP8.5. The magnitude of the source of CO2 to the atmosphere from decomposition of permafrost carbon in response to warming varies widely according to different techniques and scenarios. Process models provide different estimates of the cumulative loss of permafrost carbon: 7 to 17 PgC (Zhuang et al., 2006) (not considered in the range given above because it corresponds only to contemporary tundra soil carbon), 55 to 69 Pg (Koven et al., 2011), 126 to 254 PgC (Schaefer et al., 2011) and 68 to 508 PgC (MacDougall et al., 2012) (not considered in the range given above because this estimate is not obtained from a concentration driven, but for emission driven RCP scenario and it is the only study of that type so far). Combining observed vertical soil carbon profiles with modeled thaw rates provides an estimate that the total quantity of newly thawed soil carbon by 2100 will be 246 PgC for RCP4.5 and 436 PgC for RCP8.5 (Harden et al., 2012), although not all of this amount will be released to the atmosphere on that time scale. Uncertainty estimates suggest the cumulative amount of thawed permafrost carbon could range from 33 to 114 PgC (68% range) under RCP8.5 warming (Schneider von Deimling et al., 2012), or 50 to 270 PgC (5th to 95th percentile range) (Burke et al., 2013).

[crandles]

But do you accept that Earth hasn't so far gone into a Venus like run away?

If you do accept this, do you agree that this is strong evidence that ultimately outward radiation rising at 4th power of temperature is likely a stronger effect than the positive feedback loops and this tends to keep temperatures in a relatively stable range?

This is an interesting tack.  I wonder though, do you realize that the measurement of the Earth's energy imbalance, most clearly evidenced by the NOAA plot of Ocean Heat Content is growing at an ever increasing rate?

Yes I certainly do realise our forcing has been growing more than exponentially. If that continues then yes of course it leads to continually rising temperatures. We are forcing the climate at an incredibly fast rate. This needs to slow down markedly.

However, I believe I was commenting on feedbacks rather than forcings.

(I see that Michael Hauber also found reason to disagree with Shared Humanity post #550 so I don't appear to be alone.)

[Shared Humanity]

3. How quickly will these slow feedback loops impact the level of "earth temperature stocks? Put in a different manner, what is the doubling rate of temperature increases? Again, I have no idea.

Please keep in mind, this last question needs to be asked because systems with reinforcing loops ALWAYS result in exponential growth!

Regarding your question 2, I think what we are seeing so far is almost all a result of the forcing we are applying. Vast majority of the remainder is from fast feedback. This leaves very little if any effects from slow feedbacks. (Pedantic point: stocks are of heat energy, temperature is a measure of heat density.)

Thank you....yes..this is what I do not understand and why I posted my very unscientific comment. If the current growth behaviors are due exclusively or primarily to current human forcings then I feel much more comfortable.

[Shared Humanity]

Also...and....I did not mean to suggest, with my simple model that I believe we are heading to a Venus type problem. I am sure some significant negative feedbacks will kick in well before this.

For example: Collapse of human civilization and human induced forcings.   

[Shared Humanity]

Judging by responses, I think I've done enough damage to this discussion with my very unscientific questions and musings. I will now go back to lurking. Carry on.   

I do enjoy reading this thread, am learning a lot and will only come back to liven things up a bit.   

[wili]

Thanks for that quote, LvdL. In case some missed it, here's the takeaway:

Process models provide different estimates of the cumulative loss of permafrost carbon: ... 68 to 508 PgC (MacDougall et al., 2012) (not considered in the range given above because this estimate is not obtained from a concentration driven, but for emission driven RCP scenario and it is the only study of that type so far).

So a model that included a high value of emissions from permafrost carbon of 508 gigatons was excluded partly because it was the only one to bother to try to even makes such an estimate.

And please note that this estimate is conservative in the extreme:

[1] Alert readers may have already noticed that this article has not yet used the word “methane”. When organic matter in the permafrost is thawed and decomposes it produces mostly CO2 but also small amounts of methane, particularly so in the wetlands that are prevalent in areas of thawing permafrost.

Schuur and Abbott (2011) polled 41 experts on permafrost decay who estimated that about 3% of the carbon released from the permafrost will be in the form of methane. Methane has a restricted lifetime in the atmosphere, measured in decades, but while present in the air it has a greenhouse effect some 25 times that of CO2 over a 100-year period and higher values over shorter periods. According to Schuur and Abbott, the small amount of methane is responsible for approximately half of the warming effect from the permafrost emissions.

The UVic model does not simulate methanogenesis. That is to say that it does not model the generation of methane—all of the permafrost carbon that goes into the atmosphere in the model is in the form of CO2.

This is a significantly conservative simplification over the time period studied.

[2] Also, their model assumes only purely thermal degradation of the permafrost. Physical erosion, for example at coastlines, is not considered.

[3] Their model accounts only for permafrost down to a depth of 3.5 metres and there is plenty of carbon stored below those depths that was excluded from their modelling. [In some areas, the permafrost is about a mile deep.]

[4] Finally, this study does not consider any contribution of methane from methane hydrates, either from under permafrost or under ice sheets, nor from fossil methane currently trapped under an impermeable seal of continuous permafrost.

(My numbering)

http://www.skepticalscience.com/Macdougall.html

So that study is conservative in lots of ways, so the actual high end of the calculation should be at least twice the stated one of about 500 gigatons, just from the first consideration.

One reason feedbacks can lead to runaways (though not necessarily in this case to Venus) is because of the size of the 'stocks,' in this case, stocks of carbon releasable to the atmosphere. When you add the real stocks of carbon in permafrost to those in seabeds to those in global forests to those in terrestrial soils...you do indeed have a very large 'stock' ready to be released.

All that's needed is a mechanism...or two or three...

Those mechanisms are already underway wrt to terrestrial permafrost--direct thermal melt, as studied here; but also erosion along coasts and from runoff.

Many of the scientists that have been most directly associated with studying the relevant areas for the longest have suggested that the mechanisms for subsea permafrost melt with some dissociation of methane hydrates are already underway.

And as we have seen in various places forests (and the soils and peat under them) are burning and under threat at an enormous pace in many places around the world.

So, even if right now they are not up to the level of significant contributors, we cannot dismiss the idea that in the relatively near future, these stocks will drive a (for a time) runaway feedback mechanism that will take us relatively rapidly to a very different planetary climate, even with vast reductions in human emissions.

To me, this is all the more reason to do everything we can will all haste to diminish and then eliminate any further contribution to this cataclysm.

At this point we also have to go on to look for the most effective ways to try to re-sequester at least some of the carbon that we have so foolishly and profligately spewed into our only atmosphere (and, indirectly, into our precious oceans). But never, never can we see such sequestration schemes as excuses to UNsequester yet more carbon.

(This is all to say, partly at least, that I join crandles in pleading SH to not make himself/herself a stranger/lurker on these threads. I always find SH's contributions worthwhile.)

[Lennart van der Linde]

wili, here I'm trying hard to keep erring on the side of least drama, and you just ring the alarm bell loud and clear, you alarmist

[wili]

You nailed me!

[AbruptSLR]

The linked reference (and associated images, see captions below) was ignored by AR5 but predicts a 2-7 fold increase in the frequency of Katrina magnitude events for a 1°C rise in global temperature.  Thus even under RCP 2.6 the Atlantic seaboard will be subject to abrupt increases in inundation from the sea (again: which AR5 ignored).

Aslak Grinsted, John C. Moore, and Svetlana Jevrejeva (2013), Projected Atlantic hurricane surge threat from rising temperatures, PNAS, doi:10.1073/pnas.1209980110


http://www.pnas.org/content/110/14/5369

Abstract: "Detection and attribution of past changes in cyclone activity is hampered by biased cyclone records due to changes in observational capabilities. Here we relate a new homogeneous record of Atlantic tropical cyclone activity based on storm surge statistics from tide gauges to changes in global temperature patterns. We examine 10 competing hypotheses using non-stationary generalized extreme value analysis with different predictors (North Atlantic Oscillation, Southern Oscillation, Pacific Decadal Oscillation, Sahel rainfall, Quasi-Biennial Oscillation, Radiative Forcing, Main Development Region temperatures and its anomaly, global temperatures, and gridded temperatures). We find that gridded temperatures, Main Development Region, and global average temperature explain the observations best. The most extreme events are especially sensitive to temperature changes, and we estimate a doubling of Katrina magnitude events associated with the warming over the 20th century. The increased risk depends on the spatial distribution of the temperature rise with highest sensitivity from tropical Atlantic, Central America and the Indian Ocean. Statistically downscaling 21st century warming patterns from 6 climate models results in a 2-7 fold increase in the frequency of Katrina magnitude events for a 1°C rise in global temperature (using BNU-ESM; BCC-CSM-1-1; CanESM2; HadGEM2-ES; INM-CM4; NorESM1-M)."

First figure caption: "The frequency of Katrina magnitude surges increase greatly in a globally warming climate"

Second figure caption: "This figure shows how warming of main development region temperatures are associated with much more frequent Katrina magnitude surges."

[AbruptSLR]

The linked Jevrejeva et al 2014 reference relates PDFs for the AR5 SLR projections to an upper bound developed by expert, which shows that: (a) the AR5 SLR projections are too conservative and if there ever is an AR6 almost certainly these projections will be increased; (b) the 2014 expert opinions on an upper bound for SLR did not include consideration of Rignot et al 2014, nor Pollard 2015, findings that indicate a still higher upper bound for SLR by 2100 (see the first caption for the first attached image below), and (c) the 2014 expert opinion of the upper bound is also lower than the NOAA 2013 upper bound of 2m by 2100.

This shows that: (a) Both SLR experts and NOAA believe the AR5 SLR projections err on the side of least drama; and (b) the understanding of climate change is developing so quickly that many experts believe that instead of waiting for AR6, that the AR5 projections should be up-dated annually:

Jevrejeva, Grinsted, Moore (2014), Upper limit for sea level projections by 2100, Environ. Res. Lett. 9 104008 doi:10.1088/1748-9326/9/10/104008

http://iopscience.iop.org/1748-9326/9/10/104008/

Abstract: "We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century."

See also:

http://www.glaciology.net/Home/PDFs/Announcements/upperlimitforsealevelprojectionsby2100

First Figure caption: "Graphical representation of the full uncertainty in the sea level projections over the 21st century. It is found that there is 95% certainty that sea level rise will not exceed 1.8m this century (red). Darker purple shows the likely range of sea level rise as projected in the IPCC fifth assessment report under a scenario with rising emissions throughout the 21st century (RCP8.5)."

Extract: "The IPCC did not provide an upper limit or worst case scenario for sea level rise this century, but only a likely range of future sea level rise. In IPCC jargon "likely range" means that there is 33% chance that sea level rise will fall outside this range, and thus the IPCC high-end estimate is not a worst case scenario. I have criticized how this was communicated by the IPCC, because I thought that it was pretty clear that it would be misunderstood thus. The main uncertainty is the future rate of ice sheet mass loss and in particular the risk of a collapse of parts of the Antarctic ice sheet. This is particular challenging to model, and IPCC write that a collapse may cause sea level to rise faster than the 'likely range', but also that this risk is essentially impossible to model (paraphrased). In order to quantify the risk we therefore had to look to other lines of evidence, and here we looked at an expert elicitation which quantified the subjective uncertainty within the community of ice-sheet experts. We combined this with the IPCC numbers for the other contributions to sea level rise. The strength of this approach is that this is not just our view of the uncertainty but a snapshot of the community uncertainty. We also note that the peak in our estimate of the uncertainty distribution is very consistent with the likely range from the IPCC. The result is similar to the worst case estimate obtained by cherry-picking the worst case published result for each contributor to sea level rise (ocean expansion, glacier melt, ice-sheet melt, ground water pumping), and adding them up. This cherry picked scenario does not have a probability attached to it. Nevertheless it is useful because it strengthens our assertion that other lines of evidence are needed to justify a larger sea level rise this century.

It may seem like an alarmist paper, but really it is the opposite because we are arguing that even faster rates of sea level rise are improbable. We note that sea level rise does not stop in 2100."

See also:

http://www.glaciology.net/Home/Miscellaneous-Debris/howvulnerablearemarinebasedsectorsofantarctica

Extract: "For adaptation planning we really need the full unconditional uncertainty distribution. The above studies shows that the AR5 conditionality on no marine instability may be excluding a important part of the pdf. It appears to me to be much more than just a very remote possibility. This is also reflected in a recent expert elicitation from Bamber & Aspinall (2013). I question how useful the AR5 projections can be when used as-is for local adaptation planning."

[AbruptSLR]

The AR5 carbon budget (see Lennart's posts) focus on periods before 2050 under the assumption that RCP 2.6 will have solved the climate change problem by then, therefore, it is correct to use TCR rather than ECS values to project temperature increases; however, the linked article questions the validity of only looking up to 2050 (see extract below), when due to many considerations including: (a) thermal inertia of the oceans, (b) the initiation period required to activate many positive feedbacks such as permafrost degradation, and (c) the risk that policy makers may not be able to limit anthropogenic radiative forcing to the RCP 2.6 scenario:

http://climatechangenationalforum.org/the-answer-lies-after-2050-probably-not-before/

Extract: "The global energy system works on timescales of decades rather years. When considering the changes required in managing the climate issue, the short to medium term takes us to 2050 and the long term is 2100! As such, drawing long term conclusions based on a 2050 outlook raises validity issues."

[AbruptSLR]

wili, here I'm trying hard to keep erring on the side of least drama, and you just ring the alarm bell loud and clear, you alarmist

Not that wili is not alarming enough but he forgot to mention that: (a) The GWP for methane over a 100-year period is closer to 35 than to 25, so the ignored 3% methane emission from permafrost degradation is 70% not 50%; (b) as the amount of OH ions in the atmosphere are depleted (say due to increasing concentrations of methane in the atmosphere) that the GWP of methane increases beyond 35 times; and (c) wetting and drying (flooding & drought) cycles in the tropical rainforests due to the projected increasing frequency of strong La Nina and strong El Nino events will increase methane emissions from the rainforests of the world (as when plants that die in the droughts (El Nino) are immersed underwater due the flood periods (La Nino) emit methane (instead of CO2).  Just saying

[AbruptSLR]

The following two figures were taken from the following USACE (US Army Corps of Engineers) website for a North Atlantic District study on the coastal effects of climate change.  The first figure for relative SLR at Sandy Hook, New York shows that the USACE ignores IPCC - AR5 SLR guidance as it is too conservative.  The second figure assumes the USACE high SLR scenario by 2100 (see the first figure) and then superimposes expected increases in storm surge on the North Atlantic seaboard due to climate change (note that a design storm for infrastructure normally uses a 100-yr return period storm and a 90% CL, which the second figure indicates gives about a 3.5m design inundation event by 2100).  This indicate an abrupt increase in inundation risk for this one part of the world unless we take climate change more seriously than the IPCC AR5 does.

http://www.nad.usace.army.mil/CompStudy.aspx

[AbruptSLR]

Nicely summarized, jai.

I concur with wili that jai has made some very good points that as our Earth Systems are both out of equilibrium and to some extent masked by factors like aerosols and that the IPCC models do not account for all input and are not refined enough to provide policy makers with a clear picture of the risks that society faces from climate change.  jai has pointed out that the mean-global temperature increases that policy makers are watching today are based on radiative forcing input from 40 to 50 years ago, thus if factors included in the IPCC model projections are too conservative (non-conservative with regard to public safety) then the associated greater warming will continue for decades after policy maker finally take action (for China this will not be until 2030 and not until later for the rest of the developing world).  Many decision makers say that our highly interconnected global economy/society is too fragile to sustain the stress of a little bit of effort now to fight climate change; which, implies that if they are a little bit wrong in their estimates of the amount of damage caused by future climate change then we can all expect this fragile global economy/society to have a big negative reaction sometime after 2050.

[AbruptSLR]

Thanks AbruptSLR. I read all of your posts and understand only portions.

As I suspect that many other people also don't understand what I am implying when I provide links to the ACME project websites, I thought that I would list a first quick points off of the top of my head as to why it is important to develop such a state-of-the-art Earth Systems Model:

(a) Current models may well be underestimating the impact of climate change of regional chaotic phenomena such as large typhoons/hurricanes and strong La Nina/El Nino events that can be amplified by variables that cause such systems to resonate.
(b) The grids of the current models are not sufficiently refined to fully capture the physics of atmospheric deep convective mixing, that may be key to possibly higher than expected positive feedback from the world's tropical oceanic regions.
(c) Correctly modeling grounding line retreat of ice sheets require a dynamic model grid that captures the physics of abrupt ice retreat.
(d) The "Big Data" module can not only identify previously unidentified Earth Systems feedback mechanisms (much in the same way that derivative programs allow financial institutions to identify patterns in the market place so that the institutions can squeeze out more profit); but it can also act like a dynamic data pool for the scientists to sample from to get a better understanding of the true risks associated with Earth Systems subjected to radiative forcing.

[Michael Hauber]

Looks like a carbon budget to me.

ok, that looks like a carbon budget contained in the official IPCC reports.

[Michael Hauber]

Also...and....I did not mean to suggest, with my simple model that I believe we are heading to a Venus type problem. I am sure some significant negative feedbacks will kick in well before this.

For example: Collapse of human civilization and human induced forcings.   

Feedbacks do not in general kick in at some point.  In general the strongest effect of a feedback will be immediate, however in some cases the total impact can take a long time.  That is the fastest effect might be at time 0, but because that may only be say 1% of the total effect per year it will take a long time before the effect accumulates enough to be a significant fraction of the total effect.  Permafrost has been melting for decades, ice sheets have been melting for decades, cloudiness has been changing in whatever way its changing for decades etc etc.

However the rate of a particular effect may vary dramatically due to accidents of geography or other reasons, for instance dynamic effects on ice sheets.  Currently dynamic breakdown of ice sheets is currently in play in very limited locations - eg the end of glaicers such as Jakobshavn Glacier Greenland which world wide may be only a total of a few 100km (guesstimate) of ice sheet edge that is currently collapsing.  Potentially as glaciers continue to retreat the length of ice sheet edge that is currently collapsing could go up to many thousands of kilometres, so the effect may not be noticeable now, but could become noticeable in the future, giving the appearance of 'kicking in'. 

[Michael Hauber]

Thanks for that quote, LvdL. In case some missed it, here's the takeaway:

Process models provide different estimates of the cumulative loss of permafrost carbon: ... 68 to 508 PgC (MacDougall et al., 2012) (not considered in the range given above because this estimate is not obtained from a concentration driven, but for emission driven RCP scenario and it is the only study of that type so far).

So a model that included a high value of emissions from permafrost carbon of 508 gigatons was excluded partly because it was the only one to bother to try to even makes such an estimate.

And please note that this estimate is conservative in the extreme:

[1] Alert readers may have already noticed that this article has not yet used the word “methane”. When organic matter in the permafrost is thawed and decomposes it produces mostly CO2 but also small amounts of methane, particularly so in the wetlands that are prevalent in areas of thawing permafrost.

Schuur and Abbott (2011) polled 41 experts on permafrost decay who estimated that about 3% of the carbon released from the permafrost will be in the form of methane. Methane has a restricted lifetime in the atmosphere, measured in decades, but while present in the air it has a greenhouse effect some 25 times that of CO2 over a 100-year period and higher values over shorter periods. According to Schuur and Abbott, the small amount of methane is responsible for approximately half of the warming effect from the permafrost emissions.

The UVic model does not simulate methanogenesis. That is to say that it does not model the generation of methane—all of the permafrost carbon that goes into the atmosphere in the model is in the form of CO2.

This is a significantly conservative simplification over the time period studied.

[2] Also, their model assumes only purely thermal degradation of the permafrost. Physical erosion, for example at coastlines, is not considered.

[3] Their model accounts only for permafrost down to a depth of 3.5 metres and there is plenty of carbon stored below those depths that was excluded from their modelling. [In some areas, the permafrost is about a mile deep.]

[4] Finally, this study does not consider any contribution of methane from methane hydrates, either from under permafrost or under ice sheets, nor from fossil methane currently trapped under an impermeable seal of continuous permafrost.

(My numbering)

http://www.skepticalscience.com/Macdougall.html

So that study is conservative in lots of ways, so the actual high end of the calculation should be at least twice the stated one of about 500 gigatons, just from the first consideration.

One reason feedbacks can lead to runaways (though not necessarily in this case to Venus) is because of the size of the 'stocks,' in this case, stocks of carbon releasable to the atmosphere. When you add the real stocks of carbon in permafrost to those in seabeds to those in global forests to those in terrestrial soils...you do indeed have a very large 'stock' ready to be released.

All that's needed is a mechanism...or two or three...

Those mechanisms are already underway wrt to terrestrial permafrost--direct thermal melt, as studied here; but also erosion along coasts and from runoff.

Many of the scientists that have been most directly associated with studying the relevant areas for the longest have suggested that the mechanisms for subsea permafrost melt with some dissociation of methane hydrates are already underway.

And as we have seen in various places forests (and the soils and peat under them) are burning and under threat at an enormous pace in many places around the world.

So, even if right now they are not up to the level of significant contributors, we cannot dismiss the idea that in the relatively near future, these stocks will drive a (for a time) runaway feedback mechanism that will take us relatively rapidly to a very different planetary climate, even with vast reductions in human emissions.

To me, this is all the more reason to do everything we can will all haste to diminish and then eliminate any further contribution to this cataclysm.

At this point we also have to go on to look for the most effective ways to try to re-sequester at least some of the carbon that we have so foolishly and profligately spewed into our only atmosphere (and, indirectly, into our precious oceans). But never, never can we see such sequestration schemes as excuses to UNsequester yet more carbon.

(This is all to say, partly at least, that I join crandles in pleading SH to not make himself/herself a stranger/lurker on these threads. I always find SH's contributions worthwhile.)

Not only is permafrost melting now, but has been melting for decades.  Or is there some way that the permafrost managed to not melt during the first century or so of global warming?  Feedbacks due to melting permafrost has so far not managed to raise warming rates which over the last 35 years have been slightly lower than what the models calculate.

I would also remind you that the only peer reviewed attempt to quantify the impact of missing Carbon cycle feedbacks on IPCC projections finds that CMIP 5 models with these feedbacks predict a warming of 3.9 degrees for the next century with the missing feedbacks included compared to a warming of 3.7 degrees with them missing.  The paper also finds that current Co2 levels are overestimated by these models, so that the actual figure may well be lower than the 3.9 degrees calculated by the models.

[wili]

" the only peer reviewed attempt to ..."

I hope we can agree at least that more research is needed in this (and many other) area(s).

[wili]

"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.

...

Another phenomenon related to (or identical with?) feedback is when carbon 'sinks' stop acting as carbon sink (or stop acting as efficiently as they once did). 

This seems to be happening with non-permafrost terrestrial soils as this news study shows:

https://www.skepticalscience.com/23-year-experiment-finds-surprising-global-warming-impacts-underway.html

[Lennart van der Linde]

the only peer reviewed attempt to quantify the impact of missing Carbon cycle feedbacks on IPCC projections finds that CMIP 5 models with these feedbacks predict a warming of 3.9 degrees for the next century with the missing feedbacks included compared to a warming of 3.7 degrees with them missing.  The paper also finds that current Co2 levels are overestimated by these models, so that the actual figure may well be lower than the 3.9 degrees calculated by the models.

The abstract of Friedlingstein et al 2014 ends with:
"Global surface temperature change by 2100 (relative to present day) increased by 3.9° ± 0.9°C for the emission-driven simulations compared to 3.7° ± 0.7°C in the concentration-driven simulations. Although the lower ends are comparable in both sets of simulations, the highest climate projections are significantly warmer in the emission-driven simulations because of stronger carbon cycle feedbacks."

From a risk analysis perspective the higher ends of the projections are the most relevant. And is their range the 68% of 90% confidence interval?

The question also is what this means for lower scenarios, since MacDougall et al 2012 suggest that the permafrost feedback is relatively stronger in those lower scenarios. And what does this extra carbon mean after 2100?

And how big is this carbon feedback in Friedlingstein et al in GtC, compared to that in MacDougall et al 2012? What is their assumed ratio of released CO2  and CH4? What about the other caveats Skeptical Science mentions for MacDougall et al? Do they apply to Friedlingstein et al too? And what warming potential for CH4 should we assume, as ASLR point out?

It maybe tempting to comfort ourselves by erring, more or less, on the side of least drama, but it's risky, not conservative.

[Lennart van der Linde]

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.

[wili]

That is a good read!

Tail risk is a concept that everyone is familiar with at some level.

To take a rather obvious example, suppose an 8-year-old girl comes to a busy street which she must cross to catch her school bus. Unsure what to do, she asks an adult bystander for advice.  The adult [named Michael H?? '-)]replies that, most probably, she will make it across the street unharmed.

Any other reasonable adult listening to such advice [LvdL, ASLR...??] would regard it as radically incomplete.

[AbruptSLR]

Talking about Fat Tail (Long Tail) risks:

(a) The first attached image (from the IPCC AR4, see link below) compares model hind-casts of mean global surface temp. anoms. for combined anthropogenic and natural forcing, vs only natural forcing.  This indicates that with only natural forcing (including volcanoes) we could expect gradual cooling.  This confirms that some of the recent anthropogenic radiative forcing has been masked by natural cooling; thus as global warming gathers momentum we can expect to see a fatter (longer) PDF tail than those pointing at short-term estimates of TCR (such as the IPCC used in developing their carbon budget guidance to stay below a 2 C increase).

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/tssts-4-1.html

(b) The fourth attached image from van Vuuren et al 2011 (including many lead authors that actually developed the RCP scenaros) provides a quick over-view of the four different RCP scenarios and the first panel indicates more fat-tail (long-tail) risk above RCP 8.5 than below RCP 2.6 (note in Reply #585 I provide evidence that it is possible to use frequency counts to produce a PDF for AR5 SLR projections from different RCP scenarios and the same can be done for any AR5 projection while precipitation, mean global surface temp increase, or other values)

van Vuuren, D.P., Edmonds, J., Kainuma, M., Riahi, K., Thomson, A., Hibbard, K., Hurtt, G.C., Kram, T., Krey, V., Lamarque, J-F., Masui, T., Meinshausen, M., Nakicenovic, N., Smith, S.J., and Rose, S.K.; "The representative concentration pathways: an overview"; Cli-matic Change (2011) 109:5-31, doi: 10.1007/s10584-011-0148-z.

Furthermore, I would like to note that the RCP scenarios were calibrated base on literature that both assumed peak oil was plausible and that the Kyoto Protocol could plausibly succeed in limiting GHG emissions for RCP 2.6, but as neither of these two assumptions have been realized policy makers now point-out that emissions do not control atmospheric GHG concentrations (as in Recommended Concentration Pathways, RCP) as they can imagine ways to suck CO2 out of the sky (see the next point).

(c) The second and third attached images show that the only plausible way for policy makers to imply that they can actual limit mean global surface temp increase to 2 C is by implementing bioenergy with carbon capture and storage (BECCS) on a massive scale (note even with current international agreements we are a little above RCP 6 and with a massive global effort it might be possible to limit emissions to a RCP 4.5 level); however, climate change stress on the assumed bio-fuel and the need to feed 10 Billion people by 2050 make a massive deployment of BECCS un-reasonable.

All three of these consideration increase the fat-tail (long-tail) risks of climate change.