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An update on the Arctic sea-ice

Filed under: — rasmus @ 26 August 2012

We noted earlier that the Artic sea-ice is approaching a record minimum. The record is now broken, almost a month before the annual sea-ice minima usually is observed, and there is probably more melting in store before it reaches the minimum for 2012 – before the autumn sea-ice starts to form.

The figure shows annual variations in the area of sea-ice extent, and the x-axis marks the time of the year, starting on January 1st and ending on December 31st (for the individual years). The grey curves show the Arctic sea-ice extent in all previous years, and the red curve shows the sea-ice area for 2012.

(The figure is plotted with an R-script that takes the data directly from NSIDC; the R-environment is available from CRAN)

UPDATE on the update The National Snow and Ice Data Center announced today (August 27th, 2012) that the 2007 record has now been broken by their more conservative 5-day running average criterion. They also note that “The six lowest ice extents in the satellite record have occurred in the last six years (2007 to 2012).”


343 Responses to “An update on the Arctic sea-ice”

  1. 251
    wili says:

    Benson, my understanding is that there is quite a bit of methane at deeper levels, much of it in free pools of methane awaiting a pathway for escape. But it is true that we don’t have really accurate estimates of how much is down there, as far as I can tell. Although I haven’t heard anyone (reputable) say that if it’s all released it would not be a very significant contributor to overall GW.

    Wayne, I second your question. As I understand it, a central purpose of creating models is exactly to see where they break down so the next set of models can be perfected, and then we see where those break down, ideally in smaller and smaller areas so the models get more and more accurate over time.

    So what have we learned from these failures? What were the major factors that were left out that might have accounted for the rapid deterioration of the sea ice that we have actually seen?

    Hank, I agree, and would only add that, as Jurgen Rander recently put it, we all have to stop burning fossil fuels. I’ve come a long way, down to a small fraction of what my fellow Americans burn. But I still have a ways to go to get to zero. But for some reason, though I know that the response should be the same in any case, I still want to have as accurate picture of where we are as I can no matter how grim the truth turns out to be. I guess I kinda thought that this was one place where one could find out.

  2. 252
    François says:

    Sorry if this was covered elsewhere, but an interesting feature is the large hole in the Arctic pack, barely a few hundred kilometers away from the pole. It seems that it started out over a month ago, as a small speck on the images, roughly at the time of the Arctic cyclone. Intuitively, one would have thought that in a calmer weather, sea ice would have reformed soon afterward, closing that odd gap. Instead of that, the hole more or less regularly widened, covering tens of thousands of square km, near an -also unusual- dent on the edge of the ice cover. Persisting after so many days, and visible on just about every map (extent, concentration, temperature…), it lends credence to the expectation of an early melt of most of the ocean. Chances are, such an event could take place right at the pole, leaving plenty of room for all the submarines of the world to surface.

  3. 253
    Didactylos says:

    François, the hole in the ice isn’t difficult to explain. If you take a look at an ice age chart, you will see that the area is first year ice, and it is all disintegrating.

    It’s still unusual (the ice edge is closer to the pole than I think it has ever been) but the real unusual aspect is this year virtually every last scrap of first year ice will have melted or very nearly melted. If this happens again next year, it’s game over for the Arctic.

    I also expect that next year the transpolar drift will have pushed a big area of multiyear ice directly over the pole, which will decrease the chances that another hole will open up directly over the pole, but increase the chances that all the first year ice will be vulnerable again.

  4. 254

    Didactylos 253, well written, it is highly likely that the Pole will be ice free next year (yet again). It is a matter of an AO being negative during summer like it was in 2007 when the over all ice thickness was greater, a sure thing if so, or a slower gradual melt under cloudier conditions like what is happening now.

  5. 255
    Hank Roberts says:

    > my understanding is …
    > methane at deeper levels, much of it in free pools
    > … I guess I kinda thought …
    > this … place where one could find out.

    Want to find out what’s been published in science?
    You can get help with that here. People have tried.
    But nobody can help you “find out” what hasn’t been found yet.

  6. 256
  7. 257
    Hank Roberts says:

    ps wili, for the ‘pools’ stuff — probably that’s from Huffington Post wackywoo ‘methane tsunami’ stuff. It’s a crap site. Separate the wackywoo stuff from the published science, don’t assume one relates to the other.

  8. 258
    Hank Roberts says:

    > nice graphic
    That’s from http://www.skepticalscience.com/news.php?n=1608

    I see they’re using a curved line through the points. Is that supported?

  9. 259
    Ric Merritt says:

    Superman1, #243, says that if we suddenly ceased all FF use, we would still face temps rising to pre-industrial plus 3C.

    No one has yet bothered to comment, but my best understanding is that he (pronoun chosen based on handle!) is confusing a sudden stop in FF use with holding CO2 steady at current levels, something interesting to model though unlikely to be seen exactly in real life. Furthermore, I believe this is a common confusion.

    I would appreciate a comment confirming my take, or straightening me out if needed, from someone above my pay grade on this site, of whom there are plenty among the regulars.

  10. 260
    L Hamilton says:

    >I see they’re using a curved line through the points. Is that supported?

    In terms of the observed data a curved line is definitely supported. Gompertz, exponential or quadratic all fit minimum area, extent or volume significantly better than a straight line does. Putting it the other way round, from a statistical standpoint a straight line is *not* supported: it leaves a pattern of residuals that are systematically negative in the early years, positive in middle years, and increasingly negative again at the end. Like a textbook illustration of when the linear model is wrong.

  11. 261

    #259–“I see they’re using a curved line through the points. Is that supported?”

    IIRC, it’s a better statistical fit than linear. But I don’t have details, and am just ‘driving by’ at the moment, so can’t check right now.

  12. 262
    wili says:

    Hi hank. I do remember reading that Huff Post article.

    But I think it was this Shakhova quote that first put it in my mind. It’s not a published, peer-reviewed statement, but it is from an expert in the field (unless you care to just label anything you don’t agree with as “wackywoo”).

    “subsea permafrost acts as a lid – the seal to prevent this methane escape. And being prevented for a period of time, being sealed for a period of time, means that this gas accumulates, and it accumulates under higher pressure – this is what we have to give an example, this is what we have, for example, this bottle of champagne. So, you have a lot of gas inside, but it’s sealed for a period of time, and when you uncork this bottle, what you can see – it’s different from a bottle of mineral water left open for period of time, it’s just little bit of different. And I think that release of methane from this kind of seabed deposits disturbed by destabilization of subsea permafrost, provides a pathway for this methane – ready to go methane – because its release does not depend on production. It’s not time-dependent, it’s not temperature-dependent, it only needs the pathway to be released.”

    It’s from a _Science_ podcast. IIRC, that is a fairly reputable journal. But perhaps I’m mistaken.

    http://www.sciencemag.org/content/327/5970/1265.2.full

  13. 263
    t_p_hamilton says:

    Ric,

    Your understanding is correct. If mankind was to disappear tomorrow, CO2 levels would immediately drop and cooling would commence. The built-in warming is for constant emissions. Here is a cool java applet:

    http://carboncycle.aos.wisc.edu/index.php?page=carbon-budget-tool

  14. 264
    MARodger says:

    Ric Merritt @259
    Would this RealClimate post of 2010 suit your purpose as an explanation of the the difference between fixing today’s radiative imbalance and a complete cut-off of CO2 & other GHGs?

    Superman1 @243 did however add more agents of extra warming to his account that just today’s radiative imbalance as he points to the warming that would come from negative forcings falling to zero. The uncertainties surrounding such forcings are large but they could very well equal (& could even exceed) the present net forcings, as Superman1 implies from his calculations.

  15. 265
    Chris Dudley says:

    Hi Ric,

    Ending fossil fuel emissions leads to a reduced concentration of carbon dioxide in the atmosphere. A parametrization of what happens can be found in Kharecha, P.A., and J.E. Hansen, 2008; Global Biogeochem. Cycles, 22, GB3012

    Warming would cease fairly quickly as the concentration rapidly drops. Eventually, we’d end up at about 9% above pre-industrial if we ended emissions today. For a sensitivity of 3 C per doubling of carbon dioxide, we’d end up with about 0.3 C of warming above pre-industrial, less than the 0.8 experienced so far. Thus, cooling would be the result of ending emissions, though not completely back to the pre-industrial climate.

    Stabilizing the concentration of carbon dioxide at the present level does imply additional warming. Stabilization also required additional emissions if the final stabilization level is greater than 300 ppm or so. For stabilization at 450 ppm, we’d need about half of year 2000 emissions from about 2030 to the end of this century and then reducing down to about a quarter of that over the following two centuries. Here’s a bit of IDL code to look at that situation:

    ; To run this script in the absence of an IDL license, the Fawlty Language can
    ; be used for free. In either case, save this as a file and type '@filename'
    ; at the prompt. You could also cut and past this to the prompt in IDL.
    ;
    ; Reference: Kharecha, P.A., and J.E. Hansen, 2008
    ; Global Biogeochem. Cycles, 22, GB3012
    ;
    a=findgen(1000) ;year since 1850
    b=fltarr(1000) ;BAU concentration profile
    b(0)=1
    for i=1,999 do b(i)=b(i-1)*1.02 ;2 percent growth
    ;plot,b(0:150)*4.36+285.,/ynoz ; 370 ppm year 2000
    c=(18.+14.*exp(-a/420.)+18.*exp(-a/70.)+24.*exp(-a/21.)+26.*exp(-a/3.4))/100. ;Kharecha and Hansen eqn 1
    e=fltarr(1000) ;annual emissions
    for i=1,999 do e(i)=b(i)-b(i-1)
    d=fltarr(1000) ; calculated concentration
    t=450.-285. ;target concentration
    f=0 ;flag to end BAU growth
    for i=1,499 do begin & d(i:999)=d(i:999)+e(i)*c(0:999-i)*4.36*2. & if d(i) gt t then begin & e(i+1:999)=e(i)/1.5 & f=1 & endif else if f eq 1 then e(i+1:999)=(t-d(i+1))/4.36/2. & endfor ;factor of two reproduces BAU growth
    !p.multi=[0,2,2]
    plot,a+1850.,d+285.,/ynoz,xtit='Year',ytit='carbon dioxide concentration (ppm)',charsize=1.5 ; atmospheric carbon dioxide concentration in ppm showing target achieved
    plot,a(0:499)+1850,e(0:499),xtit='year',ytit='carbon dioxide emissions (AU)',charsize=1.5 ;emission profile to reach target in arbitrary units
    oplot,a(0:499)+1850,fltarr(500)+e(150)/2.,linesty=2 ;half of year 2000 emission level

  16. 266
    cumfy says:

    I notice at http://arctic.atmos.uiuc.edu/CT/animate.arctic.color.0.html that there is an area of sea ice just to the north of Fordovoye Island about the size of Iceland (100,000km2) which is becoming seperated and could melt within 4-5 days at current rate.

    I do think it will go and will be a significant contribution at the time it would normally be flattening out.

    Anyone else seen this ?

  17. 267
    Ric Merritt says:

    Re my #259, thanks for the answers and links. Modeling scenarios has its uses, but we shouldn’t exaggerate the real-world applicability of ones like immediate cessation of FF use, something that will happen only if most or all of us drop dead. It tends to draw attention away from the very real, indeed crucial differences between BAU and bending the curve downward with increasing urgency.

  18. 268
    Andy Lee Robinson says:

    Here’s my updated PIOMAS Arctic Sea Ice Volume animated graph from 1979 to 2012-09-02.
    A chilling illustration.

  19. 269
    Chris Dudley says:

    Ric (#267),

    James Hansen has pointed out that the atmospheric carbon dioxide concentration is going to be a climate control tool from now on. We’ll be holding it within a certain range to suit our climate preferences.

    He has proposed 350 ppm as a suitable target. It is worth knowing then that holding at 350 ppm will require some further emissions. The popular 450 ppm target actually requires substantial emissions to attain and maintain for some time to come. Making cuts now is definitely needed because, as you say, the instantaneous substantial cut won’t work, but it is worth considering this effort as our most convenient form of geo-engineering.

    This is why the Kyoto style methods will ultimately be successful. Just as everyone has an interest in currency stability, so all will have an interest in climate stability and will undertake concerted efforts to achieve it.

  20. 270
    Jim Larsen says:

    269 Chris said, ” so all will have an interest in climate stability and will undertake concerted efforts to achieve it.”

    Not even close to real. Folks with fossil fuel resources have a $5-10 cost product and consumers have perhaps a $150/barrel equivalent price to pay for alternatives. Are you saying that a .000000001% increase in CO2 concentrations will deter someone facing a 1500% profit?

    Naw, the truth is that “we” want to increase our production of CO2-generating fossil fuels while limiting “others'” production. It is pure-t-insanity to reduce fossil fuel production for any single producer, and since the lowest price where that ceases to be true is perhaps $25 a barrel, can you name ANY fossil fuel producer who will benefit from their individual choice to not drill, baby, drill?

    It ain’t consumption that matters, it’s production. Coal is the best example. The USA is reducing coal consumption. How much has that affected coal production? Not much, as the surplus is just exported. There’s always a market somewhere for expensive energy when nearly all the costs are externalized.

  21. 271
    Jim Larsen says:

    And, the more you threaten fossil fuels, the more imperative it becomes to produce them as fast as possible to get those sales in under the wire. All this AGW stuff just increases producers’ desire to sell as much as possible as soon as possible. Fossil fuels is a ~80% profit business. As if carbon taxes or anything else will change facts. Fossil fuels are useless to their owners when left in the ground, and wildly profitable at any price or tax rate when drilled. Ergo, they WILL be drilled.

    Durn, making a billion dollars will increase temps 0.01 degrees, resulting in a $10 a month increased utility bill for me. Oh well, I SUPPOSE I can live with that, assuming I can complain about Soc-ialist Government interference in the Perfect Marketplace….

    Now, those OTHER folks who don’t resemble me, well, they should stop producing fossil fuels immediately!

  22. 272
    Chris Dudley says:

    After a three day hiatus in record setting, a new record low arctic sea ice extent has been set, the sixteenth this year. http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

  23. 273
    Chris Dudley says:

    Jim (#271),

    I wonder how strong your “under the wire” argument is. Suppose, for example, that CAFE standards have limited consumption to the point that people would have to drive 48 hours a day to be able to match the oil production capacity available. At that point, where is the profit in producing more oil? It will just drive the price down below the cost of production. Oil is as profitable as it is because a cartel limits production. And, they have certainly reduced their market share in the electricity supply market by acting as a cartel. They are even losing market share in transportation.

    As there is a coal export cartel developing as well, we may see similar practices with regard to coal too.

  24. 274
    flxible says:

    For Jim and Chris, FF producers will always find a way to squeeze more profit out of dumping the costs on the commons. Shale oil is the latest “cartel”. The arctic is the next ‘commons’ [to get back on topic].

  25. 275
    Ric Merritt says:

    I am partially responsible for the OT discussion, sorry. I wanted to clarify Superman1’s OT remarks, but should have referred to them from the Unforced Variations thread.

    I think we’re into diminishing returns, so I’ll stop here, barring anything really new and important.

  26. 276
    Perk Earl says:

    I like that chart Dudley (post 272). By showing averages for the decades, 80’s, 90’s & 2000’s it’s easy to see the gap between each period is increasing. Now, if we take 2011 & 2012 as part of a new decades average, it’s easy to see this decade will again show a much bigger gap from previous decades. The gap increases will at some point cease, but only because the summertime ice extent minimums hit zero.

    On a different note, someone had a bar chart comparing melt for Greenland, with a much bigger bar shown for 2012. I lost the link – anyone have that?

  27. 277
    wili says:

    Two points on consequences of the melt:

    http://www.nature.com/news/ice-loss-shifts-arctic-cycles-1.11387

    “The cold surface layer — called the halocline — isolates the sea ice from the warmer water below.

    But the halocline is vulnerable to warming from above, says Henning Bauch, a marine geologist at the GEOMAR research centre in Kiel, Germany. A thinning halocline — something that has not yet been observed — would not only jeopardize the sea ice but could also melt the carbon-rich permafrost beneath shallow coastal waters, releasing greenhouse gases into the atmosphere.”

    And for a great (sad) video on the local and immediate consequences to Arctic life:

    http://www.youtube.com/watch?v=cE7TCvgLqo4&feature=plcp

    (Thanks to dorlomin at neven’s blog for this link.)

  28. 278
    Chris Dudley says:

    Perk (#276),

    I like those plots too. And the group that produces them is quite responsive as well. Yesterday looks like the 17th record low sea ice extent this year.

  29. 279
    wili says:

    Another perspective on the failure of the IPCC modelers to anticipate the pace of sea ice loss in the Arctic:

    http://www.aglmedia.co.uk/index.php/wasdell-ipcc

  30. 280
    Hank Roberts says:

    > failure of the IPCC modelers

    The IPCC does not have any modelers.

    The IPCC didn’t “fail” — they explained the lack of information.

    Last time, very little had been published on the subject.
    So little was available that they could not say anything!

    Don’t feed the deniers, who like to make absence of evidence into evidence of conspiracy or failure.

    I think your heart is in the right place, but accusations of failure need to be guided by the head — simply demanding that something should exist isn’t enough to make it happen, especially retroactively.

  31. 281
    Chris Dudley says:

    An 18th record low see ice extent set in 2012 yesterday.

  32. 282
    Superman1 says:

    Ric Merritt #259,

    You make the following comment:
    “Superman1, #243, says that if we suddenly ceased all FF use, we would still face temps rising to pre-industrial plus 3C.
    No one has yet bothered to comment, but my best understanding is that he (pronoun chosen based on handle!) is confusing a sudden stop in FF use with holding CO2 steady at current levels, something interesting to model though unlikely to be seen exactly in real life. Furthermore, I believe this is a common confusion.
    I would appreciate a comment confirming my take, or straightening me out if needed, from someone above my pay grade on this site, of whom there are plenty among the regulars.”

    MRodger #264 responded to your comment as follows:
    “Superman1 @243 did however add more agents of extra warming to his account that just today’s radiative imbalance as he points to the warming that would come from negative forcings falling to zero. The uncertainties surrounding such forcings are large but they could very well equal (& could even exceed) the present net forcings, as Superman1 implies from his calculations.”

    You then commented (#267):
    “Re my #259, thanks for the answers and links. Modeling scenarios has its uses, but we shouldn’t exaggerate the real-world applicability of ones like immediate cessation of FF use, something that will happen only if most or all of us drop dead. It tends to draw attention away from the very real, indeed crucial differences between BAU and bending the curve downward with increasing urgency.”

    I will address the comments above. I chose the extreme case of ending fossil fuel combustion immediately to identify the consequences of what we have done already. If we have done the analog of giving ourselves Stage 4 cancer, then we know that ANY continuation of fossil fuel combustion will accelerate a terminal situation.

    Now, in the last few days, I’ve been reading some papers on ‘climate commitment’, ‘aerosol forcing’, and ‘climate sensitivity’. There is not consensus overall among the experts, but here’s what I’ve gathered. We have generated a temperature increase of about 0.8 C above pre-industrial from the fossil fuels we have burned so far. On that issue, there is pretty much consensus. The CO2 we have placed in the atmosphere will remain there a long time even if we were to terminate fossil fuel combustion today, decreasing slowly. We can expect an additional temperature increase from this resident CO2 over the next few decades of about 0.7 C, due to the ‘climate commitment’. Some experts place the additional temperature increase at 0.6 C, but 0.6-0.7 C is the ballpark.

    But, the large uncertainty is the cooling effect if we were to terminate fossil fuel use today. Burning fossil fuels is accompanied by sulphate aerosols that go into the atmosphere, and result in increased albedo. They essentially mask much of the CO2 heat-trapping effect through this increased albedo cooling. The aerosols, unlike CO2, have a relatively short residence time in the atmosphere, on the order of days to weeks. As they leave, there is an extra heating effect. A while back, Hansen estimated this effect to be about the same as the two CO2 temperature increases listed above. These three effects would total about 3 C. Some of the more recent papers show smaller numbers for the aerosol heating , ranging from 0.5 C to 1.0 C, with the possibility that the number could be larger. The problem is the difficulty of separating climate sensitivity from aerosol forcing. My present estimate based on these more recent papers would be about 2.5-3.0 C if we were to terminate fossil fuel combustion today. A temperature increase of 2.5 C does not change my argument or conclusions based on 3 C. I see no evidence that temperature increases of this magnitude can be stabilized, given all the positive feedbacks we are seeing today with an increase of only 0.8 C.

    Obviously, we won’t stop using fossil fuels today, and my guess of the most probable scenario is that we will continue to increase fossil fuel use and CO2 emissions ad infinitum. I see no evidence of any decrease in fossil fuel use or production; all evidence I see is for unlimited production.

    I hope this clarifies my position.

  33. 283
    wili says:

    Hank @280–yes, I should have put “failure” in scare quotes. If you viewed the very short video, he makes pretty much your points.

  34. 284
    wili says:

    CT SIA keeps dropping: now 2.234 million square kilometers.

    Have these ice thickness images (right hand column) been linked here before? I find them fascinating/sickening:

    https://sites.google.com/site/apocalypse4realseaice2012/home/sea-ice-concentration-and-thickness-comparison

  35. 285
    wili says:

    A longish post of mine just got flagged as spam. It just said that, looking at the images on the right hand side of that site, plus what we know about the quality and thickness of the of sea ice, makes me realize that, really, the polar ice cap is already gone. Saying it’s still an ice sheet is like cutting down a forest, but then saying it’s still a forest since you left a couple trees and some bushes and vines still cover parts of the old forest floor.

  36. 286
    Chris Dudley says:

    I saw that I wrote see instead of sea yesterday. What a teeter-totter. A nineteenth record has occurred.

  37. 287

    While searching for a quantification of ice-albedo, I found this on the NASA site: http://conservationatwork.wordpress.com/2010/07/20/wed-2007-melting-ice-a-hot-topic/
    CERES found an albedo decrease of 0.0027, which equals 0.9 watt of energy per square meter retained in the Earth system over a 4 year period 2000-2004. If this trend is typical it would be equivalent to a doubling of CO2 over 15 years. Clearly there is more research needed, but I could not find any follow up on the NASA site. Maybe this is old hat, or was some kind of artefact, but can anyone here cast any light on this please?

  38. 288
    Perk Earl says:

    From post 263: “Your understanding is correct. If mankind was to disappear tomorrow, CO2 levels would immediately drop and cooling would commence.”

    Hmm, what about thermal inertia? I thought there was a 30-40 year gap between added CO2 and it’s impact on the oceans, which drive the weather.

    But even beyond that consideration, under what circumstances do you forsee an immediate disappearance of humankind? Aside from a catastrophe that would probably wipe out all other life as well, people will continue to burn FF. Economically there isn’t any choice. In fact, even if we knew unequivacially tomorrow that we are toast if we burn FF for one more year, we would still burn it for years thereafter because the alternative is starvation.

  39. 289
    Superman1 says:

    Perk Earl #287,

    “Hmm, what about thermal inertia? I thought there was a 30-40 year gap between added CO2 and it’s impact on the oceans, which drive the weather.”

    You are correct. The thermal inertia will result in an increase of about 0.7 C above the present delta T from pre-industrial of about 0.8 C, for a total temperature increase above pre-industrial of 1.5 C. In addition, there is a third effect from the elimination of the fossil sulphates that result from fossil fuel combustion. These sulphates increase the albedo of the atmosphere, and when fossil fuel combustion stops, the sulphates would exit the atmosphere quite rapidly (unlike the CO2, which remains for a long time). This additional temperature increase from removal of the sulphates is more uncertain than the previous two above, but has been estimated to range from 0.5 C to 1.5 C, giving a total temperature increase from these three components of from 2.0 C to 3.0 C. Given the feedbacks we are starting to see already from our present 0.8 C increase, it is difficult to believe that the ~2.5 C temperature increase could be stabilized, and not lead to a temperature runaway.

  40. 290
    Chris Dudley says:

    A twentieth record has occurred.

  41. 291
    MARodger says:

    Perk Earl @287 & Superman1 @288,
    Can I refer you to this RealClimate post of 2010 in which future atmospheric CO2 & future temperatures are considered for a ‘sudden zero emissions’ future.

  42. 292
    Superman1 says:

    MARodger #290,

    “Can I refer you to this RealClimate post of 2010 in which future atmospheric CO2 & future temperatures are considered for a ‘sudden zero emissions’ future.”

    I read it, and remain unconvinced. More convincing is the argument by Ramanathan and Feng, in PNAS. Their opening sentences are: “The observed increase in the concentration of greenhouse gases (GHGs) since the preindustrial era has most likely committed the world to a warming of 2.4 degrees C (1.4 degrees C to 4.3 degrees C) above the preindustrial surface temperatures. The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity.”

    The Ramanathan paper has been cited 70 times, while the Matthews letter has been cited nine times, two of which are self-cites. The CO2 decays very slowly from the atmosphere and, coupled with the ocean warming, produces the ‘pipeline’ effect I have outlined earlier. Add to that the removal of the increased albedo by the rapid elimination of the fossil sulphate aerosols after CO2 emissions have stopped, and you get a total temperature increase of about 2.5 C. That’s what we have committed to already, and I maintain that such a temperature increase cannot be stabilized, and will produce a new equilibrium at some higher temperature.

  43. 293
    Perk Earl says:

    Superman 1, post 288: I had read about thermal inertia but did not know the many specifics your post helped to clarify – thanks. I agree, “Given the feedbacks we are starting to see already from our present 0.8 C increase, it is difficult to believe that the ~2.5 C temperature increase could be stabilized, and not lead to a temperature runaway.”

  44. 294
    Hank Roberts says:

    > a temperature runaway.

    You need to clarify that or people will mistake it for the “we’re all going to Venus” notion, which assumes burning all the carbon.

  45. 295
    Steve Bloom says:

    Add to that ~2.5C the ~.5C from permafrost (at least). I suspect it doesn’t stop there.

  46. 296
    Superman1 says:

    Hank Roberts #293,

    “a temperature runaway.

    You need to clarify that or people will mistake it for the “we’re all going to Venus” notion, which assumes burning all the carbon.”

    I can’t be much more specific. Where the temperature equilibrates depends on the actual reserves of methane that could be released, the rate of release, the number of other substances (such as water vapor) that could be released and contribute to further warming, and the number of other positive feedbacks and how they interact synergistically. I read Maslowski’s recent review of the myriad climate models, and none of these begin to approach incorporation of the above potential contributors to temperature runaway. The increases in Arctic methane that have been reported the last few years based on temperature increases of less than a degree do not bode well, and some other already identified feedbacks further compound the problem. I wish I could be more specific, but I really have no evidentiary basis for that. Intuitively, I believe there will be no decrease in fossil fuel use, and even the unsustainable case described above of ~2.5 C increase is purely wishful thinking. I suspect far more than 2.5 C will be the reality.

  47. 297
    MARodger says:

    Superman 1 @291.
    The Ramanathan & Feng paper you cite was probably not cited by others for the purpose you propose. This is because the reference you make is not to their finding. As the final sentence of your quote (the opening lines of the abstract) makes plain, the finding you reference is simply inferred from IPCC AR4. Also this finding applies to a scenario where all GHG remain constant, as the continuing quote from their abstract shows.
    The estimated warming of 2.4°C is the equilibrium warming above preindustrial temperatures that the world will observe even if GHG concentrations are held fixed at their 2005 concentration levels but without any other anthropogenic forcing such as the cooling effect of aerosols.

    The final part of this quote about aerosols becomes clear within the paper where they explain they are using 2005 total positive forcing and zeroed negative forcings. The substance of the paper is then a discussion (after a fashion) of factors impacting on that 2.4°C warming. The paper makes a point of saying it does not answer the question “What happens if CO2 emissions cease?” which is what the ‘disappearing mankind’ question asks. The paper however does allow such a question to be answered somewhat better than the abstract alone. But that would require a certain amount of analysis.

  48. 298

    Hank, I don’t like multi decadal projections unless they project correctly near term yearly events. It can be argued that the distant future can be very chaotic, also admitting only one major outcome will demand waiting 50 years or so to confirm. Unless the time machines, the models, are accurate. GCM’s are pretty good but they fail to project Arctic ocean sea ice imminent summer demise. It would be of great service for those sitting on the fence, the “it is too long from now to act crowd” if there would be a model projecting current sea ice melts correctly. And also capable of projecting next years melt accurately as well. I am a bit perplexed that the models can’t handle sea ice as correctly as GT trends. The unconvinced waits for tangible proof, and time has not been long enough especially since 2007 . Since the stunning melt of 2007 no other sea ice models have been projecting possible outcomes. I suppose a good model will come out sooner than the next mega event??

  49. 299
    DP says:

    Why would co2 levels drop if emissions stopped? Why does nature seek to reduce concentrations above pre-industrial levels?

  50. 300
    Toni says:

    Hello,

    I wonder if I may ask a question, in respect of the following BBC News item, which made me wonder….

    http://www.bbc.co.uk/news/technology-19576266

    1) Ice breakers weaken the ice in winter, when one might expect it to have a chance to re-form  the volume and thickness it might otherwise achieve, if left intact.

    2) Higher mean temperatures cause melt at the margin of EACH piece of ice created by this mechanical fragmentation, multiplying the melt effect by a fractal effect on this hugely greater surface area and volume, with deeper penetration.

    3) The resulting, cracked surface has a lower albedo and so absorbs more radiative energy than a pristine, intact ice cap with its high reflective index.  This may be smaller, but over a wide area, significant temperature difference increase.

    I wonder why this factor is never discussed, and yet Russia is now planning a nuclear ice-breaker, precursor to more forays into the pack ice.   I have been scanning the scientific press and see no reference to this mechanical effect, which may have contributed to accelerating the  extent and depth of melt rates, by increasing the surface area exposed to thermal effects of solar radiation.

    It should be easy enough to establish the impacts of fragmentation, experimentally, and even assign a value to the degree of fragmentation.  

    At a time when we are seeing unprecedented melting of Arctic sea ice…

    SHOULD THE USE OF ICE BREAKERS IN THE ARCTIC NOT BE FORBIDDEN BY AN INTERNATIONAL TREATY?

    Just a thought….

    Best Regards.

    Toni M
    Bristol, UK


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