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  1. Great post!… A few questions…

    I myself was taken aback by the Allan Frame discussion to the effect that we can lowball the estimate in confronting climate change and always revise it upwards if needed. Particularly since 3 C is so well supported by Annan and Hargreaves (2006).

    One thing I am curious about within this context: Hansen has been using a value of 3 C at least since 1993. However, this is what he calls the short-run Charney climate sensitivity and argues that in the long-run given feedbacks from elements in the climate system which are treated in the short-run as boundary conditions, the long-term climate sensitivity is more like 6 C.

    I quote:

    Hansen et al. (1993) calculated the ice age forcing due to surface albedo change to be 3.5 +/- Wm^-2. The total surface and atmospheric forcings led Hansen et al. (1993) to infer an equilibrium global climate sensitivity of 3 +/- 1C for doubled CO2 forcing, equivalent to 3/4 +/- 1/4 CW^-1 m^-2. This empirical climate sensitivity corresponds to the Charney (1979) definition of climate sensitivity, in which ‘fast feedback’ processes are allowed to operate, but long-lived atmospheric gases, ice sheet area, land area and vegetation cover are fixed forcings.

    pg 1929

    Climate sensitivity with surface properties free to change (but with GHG specified as a forcing, a choice relevant to the twenty-first century) is defined in figure 1, which reveals Antarctic temperature increase of 3 C (Wm^-2)^-1. Global temperature change is about half that in Antarctica, so this equilibrium global climate sensitivity is 1.5 C (Wm^-2)^-1, double the fast-feedback (Charney) sensitivity.

    pg. 1944

    Hansen, J., Mki. Sato, P. Kharecha, G. Russell, D.W. Lea, and M. Siddall, 2007: Climate change and trace gases. Phil. Trans. Royal. Soc. A, 365, 1925-1954, doi:10.1098/rsta.2007.2052
    http://pubs.giss.nasa.gov/abstracts/2007/Hansen_etal_2.html

    Additionally it would seem that so long as one is dealing with only the short-run, in principle at least, climate sensitivity should be well-defined as one is dealing principally with the feedback from water vapor and sea-ice. One does not have to worry about instabilities associated with ice sheets, feedback from the carbon cycle (even though this would seem to already be coming into play), or instabilities associated with ocean circulation.

    In Annan et al, much of their analysis was dealing with fast feedbacks, but some mention of comparisons between the most recent ice age and today were mentioned which would suggest that long-term feedbacks were being included. In particular it would appear to involve ice sheets.

    Is this consistent with Jim Hansen’s analysis? Likewise, is it possible that Roe and Baker are in some way blurring the distinction between short-term and long-term? At a deeper level, what do you see as being the relationship between the three analyses?

    [Response: Thanks for the thoughtful comment. My response probably won't go into the detail that you want, I'm afraid, though others may want to chime in. But I can answer some of your questions. Roe and Baker, I would say, are not really making this distinction at all. As you correctly point out, the longer-term effects of ice sheets, etc. can amplify things further, but this could be said to be included in the uncertainty in f in Roe and Baker. (Though ice sheets are an example of a very non-gaussian distribution in f). Annan and Hargreaves analysis effectively looks at the short term only, since they treat the ice albedo as a forcing, not a feedback. --eric]

    Comment by Timothy Chase — 26 Oct 2007 @ 1:49 PM

  2. Does the “business as usual” referred to here include the recent findings about substantially faster growth in CO2 emissions than predicted, saturation of carbon sinks, and arctic ice melting?

    There’s been so much bad climate news lately it seems like AR4 was just wishful thinking!

    [Response:When I said "business as usual" in the post, I'm simply referring to the A2 scenario of the IPCC, which hasn't changed (I think) since TAR. --eric]

    Comment by EthanS — 26 Oct 2007 @ 2:02 PM

  3. Unfortunately, in the policy realm there is often a trade off between efficiency and flexibility. Firms want a fair degree of price certainty in long-term investment decisions, and the allocation of carbon-based assets (like permits) make a reduction of permits in circulation in response to reductions in scientific uncertainty somewhat problematic.

    In general, its much easier to loosen a climate policy than tighten it.

    Comment by Zeke Hausfather — 26 Oct 2007 @ 2:47 PM

  4. “(…) initial targets of much lower than 450 ppm (…)” Er, the current level of 381 ppm is only 15% lower than that, and is it reasonable to call it “much lower”? Doesn’t seem like it…

    Re #1: Timothy, if I’m reading Hansen correctly that extra 3C is more or less a one-time pulse associated with ice sheet melt; IOW sensitivity returns to 3C after they’re gone. What’s not clear from my admittedly inexpert reading of the paper is whether that transient sensitivity goes away (with the ice sheets) with that initial 3C. I’d love an answer to that.

    Comment by Steve Bloom — 26 Oct 2007 @ 2:56 PM

  5. I fail to see how ‘uncertainty’ supports the skeptics position. We have done a great deal to elimiante low-end climate sensitivty- and it seems we can attribute ~3 C per 2x CO2 with high confidence (anything lower than 2 now seems very unlikely). In the political arena, things like natural variablity and uncertainty are introduced quite often, but in Science, the logic is reversed: if the past is more variable than we think, or the more uncertainty in higher-end projections, the more worry for the future. It appears that real world observations and not the wishful thinking of “uncertainty” shows that if anything, problems are arising faster than anticipated. With a highly variable past, and with the uncertanties in feedbacks and tipping points, you can hope for an exact cancellation of human effects, but you can also fear a great amplification. The CO2 physics is easy, the water vapor is pretty easy, we still have more to understand about aerosols and clouds or ocean circulation, but you can’t just say this means there is no problem- it doesn’t follow.

    Really, such efforts to hide behind what we don’t know (implying we know nothing) demonstrate the intellectual bankruptcy of those who say ‘do nothing.’ This paper from RC’s own Ray Pierrehumbert shows some of the things at risk. A more-variable hence higher-feedback world would indicate bigger future changes, and this is nothing trivial, so bashing climate models or some things that still need to be worked out won’t make the AR4 WG2 report on impacts go away.– Chris

    Comment by Chris C — 26 Oct 2007 @ 3:01 PM

  6. Thus conservative strategies would seem in order, which probably implies initial targets of much lower than 450 ppm, and still subject to further revision.

    And yet even the EU’s target is 550 ppm, not even close to 450; and I haven’t heard that any governments are seriously talking about implementing a target lower than 550 ppm. :-(

    (I’ve seen “450-550 ppm” quoted, but in practice that is really the same as a target of 550 ppm).

    Comment by Dave Rado — 26 Oct 2007 @ 3:08 PM

  7. Present CO2 levels are about 384 ppmv, the present rate of increase is about 2 ppmv/yr, if the present rate remains constant we’ll hit 450 in just 33 years — right around 2040. But as comment #2 points out, emissions are growing and sinks are reducing.

    So, is setting targets to be *less* than 450 at all realistic? Does all of this add to the urgency of limiting carbon emissions?

    Comment by tamino — 26 Oct 2007 @ 3:29 PM

  8. I am an advocate for setting a much lower goal for CO2 concentrations: 315 ppmv.

    This was the value in 1950, when the direct atmospheric measurement sequence began. Also, at that value, the relative forcing would be about 1/3 of the current value (leaving out methane, NOx, aerosols, black carbon, etc.)

    Comment by David B. Benson — 26 Oct 2007 @ 3:31 PM

  9. Steve Bloom (#4) wrote:

    Re #1: Timothy, if I’m reading Hansen correctly that extra 3C is more or less a one-time pulse associated with ice sheet melt; IOW sensitivity returns to 3C after they’re gone. What’s not clear from my admittedly inexpert reading of the paper is whether that transient sensitivity goes away (with the ice sheets) with that initial 3C. I’d love an answer to that.

    I would agree that the sensitivity, at least as the result of ice sheets will be a one-time afair, but as we are losing ice sheets, the temperature will rise in accordance with the 6 C long-run, so if one doubling takes us up to 6 C and then there are no more forcings, then we will remain at 6 C until the CO2 begins to drop.

    6 C is something that I would like to see us avoid at any point, whether it be by the turn of the century or 500 yrs hence.

    Comment by Timothy Chase — 26 Oct 2007 @ 4:14 PM

  10. Re #8: Oops. radiative forcings, not relative.

    Comment by David B. Benson — 26 Oct 2007 @ 4:41 PM

  11. And I think this issue of climate sensitivity doesn’t consider where those extra GHGs come from and “nature’s sensitivity” to the warming & its many effects. It might be that most come from our direct emissions, but they could also come from nature not uptaking as much as it has been (due to the heat, CO2 overload, and/or all the many effects from global warming and increasing CO2 in the atmosphere, and ocean acidification, and subsidiary effects (from measures that emit GHGs), such as pollution and acid rain harming forests, plants, and soils)….

    And/or it could come from nature emitting GHGs as a response to the warming and its many effects (right now I’m thinking wildfires, but there’s also methane from melting permafrost & ocean hydrates).

    So there is this other uncertainty to consider — not only climate sensitivity, but nature’s sensitivity to and response climate change, and how much extra GHGs (and thus warming) that might entail.

    See: Methane Bubbling From Arctic Lakes, Now And At End Of Last Ice Age http://www.climateark.org/shared/reader/welcome.aspx?linkid=86725

    To be on the safe side so that the computers don’t go into infinite do-loops on this, might help to set some articificial constraints or cut-off point subroutines.

    Comment by Lynn Vincentnathan — 26 Oct 2007 @ 5:07 PM

  12. Re. #5: “I fail to see how ‘uncertainty’ supports the skeptics’ position.” It doesn’t, but take a look at the responses to New Scientist’s coverage of this paper and you’ll see that they average sceptic-in-the-street doesn’t actually respond to the real science:
    http://environment.newscientist.com/article/dn12833-climate-is-too-complex-for-accurate-predictions.html

    Comment by Hudson Pace — 26 Oct 2007 @ 5:21 PM

  13. In the Roe & Baker paper, I’m not at ease with the switch between purely analytical considerations on one hand, and physical considerations on the other (and it’s a quite a complex paper).

    For example, if f (the feedback factor) is negative (why not from a purely analytical point of view), should we assume that S (climate sensitivity) rapidly tends toward very low values ?

    Comment by Charles Muller — 26 Oct 2007 @ 5:33 PM

  14. Re #13, Roe and Baker says, “if f > 0, which appears to be the case for the climate system.” There seems to be general agreement on this point.

    Comment by Karen Street — 26 Oct 2007 @ 6:17 PM

  15. I am sorry, but I must make a rude response.

    The climate models did not predict last summer’s ice retreat or anything like it in the near future. The ice melt has been attributed to possible “anomalies” in the atmospheric circulation patterns or changes in the ocean currents. If we plot Arctic Sea Ice anomalies in terms of standard deviations from a baseline, then the combination of the summers of 2005 and 2007 starts to look like a real trend – that the models missed.

    Therefore, it is likely that feedback mechanisms are missing from the GCM. Thus, I am skeptical of climate sensitivity numbers developed from the current generation of GCM. If I were making policy decisions that affected billions of people for generations to come, I would apply a generous safety factor, of at least 2 and maybe 10. If I wore a bow tie, (the low risk option), I might use a safety factor of 20. That implies putting the brakes on greenhouse gas emissions now! That means putting the brakes on HARD!

    Consider the rapid increase in the number of moulins on Greenland over the last few years. Consider the rain events across broad swaths of Greenland last summer. Those rain events transfered heat from the ocean to the ice. The moulins allow that heat to be transferred rapidly into the depths of the ice. (This is a heat transfer that is not in the GCM.) My experience is that when ice gets rained on, it falls apart and slides down the hill.

    Do not worry about the economic impacts of putting the brakes on greenhouse gas emissions. Soon, (sooner than Al Gore dreams), we will have a problematic episode of sea level rise, and all the costs of reducing greenhouse gas emissions will seem trivial. However, by then, we will be at higher levels of emissions, there will be more panic, and the costs of abruptly reducing greenhouse gas emissions will be much higher.

    Comment by Aaron Lewis — 26 Oct 2007 @ 6:34 PM

  16. #14 Yes but precisely, this agreement is rather empirical, a kind of prior assumption that Roe and Baker try to avoid in their paper. After all, there’s also something like a general agreement from paleoclimate that 2xCO2 will not provoke a ∆T of 15°C. But if I see fig.1 in the paper, it’s an analytical eventuality if f -> 1. So, I dont’ clearly understand why the low range of the ∆T is not 1°C (f = 0, so just the ∆T due to 2xCO2 without feedback) or even less (if f is negative for unknown reasons in our present understanding of climate). But I’m going to read more carefully the paper, there’s probably the answer.

    Comment by Charles Muller — 26 Oct 2007 @ 8:37 PM

  17. Actually, from the point of view of risk management, one multiplies probability by the cost of the scenario. Since cost probably increases quite super-linearly with temperature, it is possible that the tails of the distribution could dominate risk even though they are quite improbable. In this case, the appropriate course would be to spend considerable effort to nail down the feedbacks while concentrating mitigation efforts on the more probable outcomes. A flexible system such as cap and trade would likely be essential if we found that the worst-case feedback values were more probable than originally anticipated. A very interesting risk scenario.

    Comment by Ray Ladbury — 26 Oct 2007 @ 9:10 PM

  18. Would it be correct to say, then, that, for infinitessimal changes, in the absense of sharp thresholds, the climate sensitivity tends to be predictable as the climate itself is more similar, but as changes get larger, the sensitivity may grow or shrink; and that the climate must change significantly before significant sensitivity shrinkage would be expected (if it were to shrink), which is why it is easier to bracket the low end than to bracket the upper end, where more change leads to more change in sensitivity which amplifies change even more?

    Comment by Patrick 027 — 26 Oct 2007 @ 9:53 PM

  19. RealClimate’s conclusion seems a good summary for policy-makers of Roe and Baker’s work: “climate sensitivity is uncertain, but we can pretty much rule out low values that would imply there is nothing to worry about. The possibility of high values will be much harder to rule out.”

    It is a pity that Roe and Baker did not say something as clear as that in their article because it leaves their work open to abuse by people trying to undermine the momentum for major policy changes.

    Allen and Frame’s suggestion that we should “resist the temptation to fix a concentration target early on” because “Once fixed, it may be politically impossible to reduce it” seems hard to reconcile with their faith in “our descendants [having] the sense to adapt their policies to the emerging climate change signal …”. They seem to think our descendents will act sensibly but we will not.

    Comment by Chris McGrath — 26 Oct 2007 @ 9:57 PM

  20. Re #16, Roe and Baker don’t address why climatologists feel f to be positive. But when all factors are accounted for, the net result is positive, or in the same direction as the change. Examples include:

    • albedo decreases as ice melts (ice is perhaps 80% reflective, while ocean albedo can be as low as 3.5%)
    • increased water vapor in a warmer climate
    • warmer oceans absorb less carbon dioxide
    • warmer soils release carbon dioxide and methane
    • plants in a hotter climate are darker

    Negative feedbacks may include shifts in clouds.

    A long time ago, there were questions about whether positive or negative feedbacks would dominate.

    Comment by Karen Street — 26 Oct 2007 @ 10:07 PM

  21. #15, Aaron is correct about sensitivity doubts in the present tense.
    Current 2007 Northern Hemisphere temperature anomalies were riding very warm until the great Ice melt, I won’t be surprised to see a return of very strong positive anomalies starting with this October’s NH Monthly result, as the Polar ice sheet returns to its nearly full but quite thinner extent. Energy transfers between sea, air and the cryosphere may be ill defined by a simple sensitivity of uniquely the lower troposphere. I would agree with the assessment given here that sensitivity will exist at a higher rather than lower figure, because it is already quite strong, only if it shows up near the ground.
    Sensitivity variances should be norm not the exception.

    Comment by Wayne Davidson — 26 Oct 2007 @ 11:44 PM

  22. RE # 15

    Notice that the Arctic Sea Ice is recovering very slowly, much slower than in previous years.

    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.365.jpg

    The anomaly is more negative now that it was this summer.

    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.anom.jpg

    Will the anomaly keep growing? I suspect that there is a fair change that the anomaly will mostly continuing to grow, perhaps until the Arctic is almost sea ice free. If so, the Arctic might be almost sea ice free by next summer, or the summer after that.

    Comment by Phil Hays — 27 Oct 2007 @ 12:00 AM

  23. Gerard Roe was interviewed on BBC News today and I wasn’t impressed – what he said was accurate, but imagining myself into the mind of a “sceptic-in-the-street”, I would have certainly have got the impression from the interview that the science was far too uncertain to justify taking any action at all to reduce emissions. Another case, IMO, of a scientist not being able to imagine how an ordinary layman is likely to interpret what they say, and how to communicate with the public in language that they will not misinterpret.

    Comment by Dave Rado — 27 Oct 2007 @ 1:38 AM

  24. Ref 20 Phil writes “Will the anomaly keep growing? I suspect that there is a fair change that the anomaly will mostly continuing to grow, perhaps until the Arctic is almost sea ice free. If so, the Arctic might be almost sea ice free by next summer, or the summer after that.”
    According to NOAA/NSIDC the amounts of arctic sea ice in different months was as foillows:-
    March 2006 14.4 million sq kms
    March 2007 14.7 million sq kms
    September 2006 5.9 million sq kms
    September 2007 4.3 million sq kms

    Anyone like to put their name on what future values will be? I will try and keep the values and names and post them at an appropiate time in the future. My two guesses are as follows. March 2008 14.2 million sq kms. September 2008 4.8 million sq kms.
    It should be remembered that in 2005 the accumulated cyclone energy (ACE) value in the North Atlantic was around 250. In 2006 it was around 70, and this year to date is around 60. Will history repeat itself?

    Comment by Jim Cripwell — 27 Oct 2007 @ 3:47 AM

  25. In a recent peice in the independent it was stated that climate models had underestimated CO2 release by 37% overall and the worse case scenarios of the IPCC were already inadequate.

    http://environment.independent.co.uk/climate_change/article3087271.ece

    A dramatic decline in the ability of the Earth to soak up man-made emissions of carbon dioxide, and a corresponding acceleration in the rate of increase of greenhouse gas in the atmosphere, have been detected for the first time by scientists.

    This two pronged feedback must be very difficult to model accurately and the oft stated view of RC that delta is 3 C does not tell us when this is going to happen.

    I know that it is a left wing peice and people referenced in the speice may have been misquoted but it is lending itself to the notion that the present warming is coming forwards by decades.

    The worst thing about AGW is the rate of change which is putting unprecedented stress on earths systems to deal with humans CO2 emissions. Surely there are feedbacks everywhere and the non linear nature is likely to be greater if the rate of change is?

    Comment by pete best — 27 Oct 2007 @ 5:04 AM

  26. Re #20. I recently had an email exchange with Bill Chapman at Cryosphere Today about the likely change in the anomaly over the winter. Without posting his email on this public site, I’ll summarize. Basically he confirmed my amateur guess: that the arctic winter is invariably long enough and cold enough to freeze essentially all of the surface water of the arctic ocean. The onset of this freezing has been delayed and slowed by the unusual warmth of the water, which is why the anomaly has increased since the start of winter. But it is coming. So he’s expecting the anomaly to rapidly become less negative, within the next month or so.

    So the ocean is going to skin over with ice this winter, as it always does. This is an inevitable consequence of the axial tilt: the only way the ocean could stay unfrozen through February would be for it to start the winter very warm indeed. Thus the winter maximum area is thought to be much less sensitive than the summer minimum area.

    However, unless this winter is unusually cold, the ice will be very thin (as it will have had less time to form). So if we have normal melt season weather next year, there will be a large anomaly again. If the melt season is like 2005 or 2007, all bets are off.

    I hope I’ve summarized Chapman correctly. In short, expect the anomaly to head back towards 1 million square kilometres very soon, but only for a season.

    Comment by Nick Barnes — 27 Oct 2007 @ 5:33 AM

  27. re #19

    Kareen

    “albedo decreases as ice melts (ice is perhaps 80% reflective, while ocean albedo can be as low as 3.5%)
    • increased water vapor in a warmer climate
    • warmer oceans absorb less carbon dioxide
    • warmer soils release carbon dioxide and methane
    • plants in a hotter climate are darker

    Negative feedbacks may include shifts in clouds. ”

    not entirely agree with you.

    for the oceans there is the possibility of “surface” (100 to 200 m thickness) ocean waters to cool stronger than forecasted.
    Think about the wind-driven upwelling and please look at actual SST SH trend.
    For the clouds we don’t know the exact amount of future low and high clouds.
    There is also a fertilization effect of CO2.

    I’m not a denialist but I’m very worried by the certitude of some people here and by the absence of response, from contributors, when there is some unconvenient question.

    Comment by Pascal — 27 Oct 2007 @ 7:55 AM

  28. RE #21, I wonder if perhaps the authors do know how layman will interpret what they say….

    Comment by Lynn Vincentnathan — 27 Oct 2007 @ 8:08 AM

  29. A quick weigh-in on a minor point that I, a sceptic, wish to clarify. I believe the mathematical uncertainties discussed here neither enhance nor detract from valid scepticism. Uncertainties and probabilities are simple facts of science (they can be consciously manipulated, but I don’t see that here). I will admit that some sceptics might jump on the changing uncertainties, but I can’t help that. I am a little chagrined that some here desperately want to take only the worst case (like some sceptics want only the “best” case) and make that gospel or even worse, to the point of “over reaction” to be on the “safe” side as two or three here have implied, and to the point of not disclosing the true stuff which only give sceptics fodder, as Hudson (12) and Dave (21) imply. I don’t think the uncertainties per se or even the changing uncertainties make or break the science of AGW in any way, though might have an effect on what to do, ala Ray’s #17.

    Comment by Rod B — 27 Oct 2007 @ 9:59 AM

  30. Aaron Lewis Says:
    26 October 2007 at 6:34 PM”

    The climate models did not predict last summer’s ice retreat or anything like it in the near future. The ice melt has been attributed to possible “anomalies” in the atmospheric circulation patterns or changes in the ocean currents. If we plot Arctic Sea Ice anomalies in terms of standard deviations from a baseline, then the combination of the summers of 2005 and 2007 starts to look like a real trend – that the models missed. … Do not worry about the economic impacts of putting the brakes on greenhouse gas emissions. Soon, (sooner than Al Gore dreams), we will have a problematic episode of sea level rise. …”

    I guess I don’t understand how a climate model could reflect a linear expectation for centuries and also contain a trigger for a nonlinear collapse within the timeframe of the organizer on Al Gore’s Blackberry.

    Comment by J.C.H. — 27 Oct 2007 @ 9:59 AM

  31. http://www.jpl.nasa.gov/news/news.cfm?release=2006-107

    “The researchers are examining what caused the rapid decrease in the perennial sea ice. Data from the National Centers for Environmental Prediction, Boulder, Colo., suggest that winds pushed perennial ice from the East to the West Arctic Ocean (primarily located above North America) and significantly moved ice out of the Fram Strait, an area located between Greenland and Spitsbergen, Norway. This movement of ice out of the Arctic is a different mechanism for ice shrinkage than the melting of Arctic sea ice, but it produces the same results – a reduction in the amount of perennial Arctic sea ice.”

    “Nghiem cautioned the recent Arctic changes are not well understood and many questions remain. “It’s vital that we continue to closely monitor this region, using both satellite and surface-based data,” he said.”

    Who knew? Could someone please point me to the literature on AGW causing more wind.
    Thanks.

    Comment by Ellis — 27 Oct 2007 @ 12:41 PM

  32. Ellis, no surprise there. You’ll find a lot of denial sites this week claiming the wind isn’t connected to climate change. Look up
    Arctic climate regime index (ACRI).

    That’s a known reversing pattern — positive ACRI phase characterized by cyclonic ocean circulation and a warmer and wetter climate.

    Like El Nino/La Nina and much else in the climate system, these go back and forth.

    What happens when the average temperature matches what used to be the intermittent extreme temperature?

    In the polar regions — where warming happens fastest — what happens more often? It’s warmer and wetter. It was raining near the North Pole when the Polarstern icebreaker got closest to the Pole during the summer. Does the wind pattern change along with the temperature? Let’s see.

    You ask who knew? The climate scientists.
    Who had no clue? The people trying to pretend nobody knew.

    Comment by Hank Roberts — 27 Oct 2007 @ 1:13 PM

  33. Further to Aaron’s post in #15, if the current generation of GCM’s do not properly include ice sheet dynamics and interactions with the oceans etc, are not the pdf’s and their moments compromised and if so to what extent? Given such incompleteness (effectively a Gibbs-type phenomenon), what level of robustness or convergence can be ascribed to the parameter which people refer to as climate sensitivity? Furthermore, what physical meaning can be given to such a parameter given the incomplete spanning set for the overall system?

    Comment by mg — 27 Oct 2007 @ 2:11 PM

  34. Pascal (#27) wrote:

    Negative feedbacks may include shifts in clouds. ”

    not entirely agree with you.

    for the oceans there is the possibility of “surface” (100 to 200 m thickness) ocean waters to cool stronger than forecasted.

    Think about the wind-driven upwelling and please look at actual SST SH trend.

    For the clouds we don’t know the exact amount of future low and high clouds.

    There is also a fertilization effect of CO2.

    Agreed: there are a few negative feedbacks. And it is certainly worthwhile to point them out. But I would be careful, too, as what is a negative feedback may also be feeding into a positive feedback and as a result of its indirect effects may on the whole be more positive than negative.

    For example, as the tropics become warmer, there is more poleward circulation in both the ocean and atmosphere. Negative feedback? Well, this cools the tropics and cuts in to the potential for a super greenhouse effect where the rate of downwelling longwave increases relative to surface temperature more rapidly than upwelling longwave.

    But it also means that more ice is going to melt, and with the albedo effect that is a negative feedback feeding into a positive feedback. However, once the ice is melted it will no longer be able to feed into the albedo effect. So it is quite possible that the net effect is currently positive but will later become negative.

    Alright, how about winds resulting in the upwelling of deep water and the downwelling of surface water? Insures that things won’t warm topside as quickly, therefore it is a negative feedback. However, in the Antarctic Ocean this is bringing up organic material which releases both carbon dioxide and methane.

    It is precisely this upwelling which has resulted in the recent diminished capacity of the Antarctic Ocean to absorb as much of our carbon emissions. So at least in the case of the Antarctic Ocean (the main door to the biggest sink for carbon dioxide our climate system has) it would appear that this may very well be a net positive feedback – at least for the time being.

    CO2 fertilization?

    Well, that seems to have worked for a while, but as temperatures rise due to higher CO2 concentrations plants become subject to both heat and drought stress, and so we have that sink working less well than it has in the past — which is a feedback. Besides, I am not really sure that we would have ever considered CO2 fertilization to be a negative feedback in as much as it would have simply meant that less CO2 was building up and therefore couldn’t act as a climate forcing.

    I believe the way that they would have handled it (although I could very well be wrong) is the assumption that so much of the carbon which we emit expressed as a percent will be taken up by that sink – prior to any climate forcing/feedback analysis. However, when that sink begins to become less effective, the percent falls, and the diminished capacity to absorb our carbon emissions would be counted as a feedback.

    Pascal (#27) wrote:

    I’m not a denialist but I’m very worried by the certitude of some people here and by the absence of response, from contributors, when there is some unconvenient question.

    They will chime in when they can, but their jobs would seem to keep them fairly busy. In the meantime people like you and me can try and help out. Thank you for doing so.

    Comment by Timothy Chase — 27 Oct 2007 @ 2:15 PM

  35. #31 Not winds as much as advection of much warmer air, not only on the surface but also in the Upper Air, exactly where AGW affects the atmosphere.

    #30, The non linear element is found in transferance of energies in the three main bodies at play, water, air and ice (with snow). It is predictable if the models include all three.

    #26 Lynn, Its a big problem, or failure when science literature is mangled according to point of views driven by special interests. I think a paper such
    as from Roe and Baker is designed for other scientists to mull over the merits of
    using sensitivity as a benchmark. It would be convenient for contrarian politicians to interpretret sensitivity estimates to design policy, since it is so uncertain there would be no policy….

    Comment by Wayne Davidson — 27 Oct 2007 @ 2:33 PM

  36. Hank,
    could you please point me to where you got the information about a positive ACRI phase. When I went to
    http://www.arctic.noaa.gov/essay_bond.html
    there was no information as to ACRI phases. Perhaps, you meant the AO is in a positive phase, in which the site says,”The Arctic Oscillation (AO) appears to be the cause for much of the recent changes that have occurred in the Arctic. Its effects are not restricted just to the Arctic; it also represents an important source of variability for the Northern Hemisphere as a whole. The AO has been described as “a seesaw pattern in which atmospheric pressure at polar and middle latitudes fluctuates between positive and negative phases. The negative phase brings higher-than-normal pressure over the polar region and lower-than-normal pressure at about 45 degrees north latitude. The positive phase brings the opposite conditions, steering ocean storms farther north and bringing wetter weather to Alaska, Scotland and Scandinavia and drier conditions to areas such as California, Spain and the Middle East.”" Of course hasn’t the AO been in a positive phase since around 1980.

    Hank states,”That’s a known reversing pattern — positive ACRI phase characterized by cyclonic ocean circulation and a warmer and wetter climate.”

    What is a known reversing pattern?

    Hank states,”In the polar regions — where warming happens fastest — what happens more often? It’s warmer and wetter.”
    This sentence is not very clear, although I will agree where it is warmer, warming happens more often, I am not sure that you can definatively state “polar regions” since readings from antarctica and the arctic seem to be heading in opposite directions.

    Hank states,”Does the wind pattern change along with the temperature? Let’s see.”
    Careful, that sounds a lot like weather, pardon me, noise. Does the “let’s see” indicate that nobody knows and we will just have to wait and see? Or was that just an incomplete thought? Of course, I expect that there is some literature out there that makes the connection between wind and AGW, and after all that is all I asked for in the first place.
    Thanks again.

    Comment by Ellis — 27 Oct 2007 @ 3:09 PM

  37. Thank you Wayne #35, however, from reading the link I provided in #31, I think it is pretty clear that they are talking about the actual force of the wind pushing the ice to warmer climes, and not the winds being warmer.

    Comment by Ellis — 27 Oct 2007 @ 3:20 PM

  38. #36, Ellis, I missed that 2006 bit. I was referring to 2007 where the best link is:

    http://arctic.atmos.uiuc.edu/cryosphere/sea.ice.movie.2007.mov

    Where you can judge for yourself what happened especially after several views!

    Comment by Wayne Davidson — 27 Oct 2007 @ 3:52 PM

  39. Re. Rod B, #21:

    to the point of not disclosing the true stuff which only give sceptics fodder, as Hudson (12) and Dave (21) imply.

    If you really think I implied that you completely misunderstood me. I simply think it’s important to communicate the accurate science in a way that is unlikely to be misinterpreted by laymen.

    Comment by Dave Rado — 27 Oct 2007 @ 4:35 PM

  40. Re 33
    These models are science tools. If we want to use them for engineering or planning, or policy development, we should apply safety factors. Planners, engineers, and policy makers are going to have to build new tools that are informed by the science, but are not THE science. Engineers need tools that meet the needs of engineers. Planners need tools that meet the needs of planners. Why should a tool that scientists built for themselves be suitable for planners, engineers, and policy makers? That was not part of the design basis. Nowhere in funding documents does it say, “Build a tool that does everything for everybody!”

    Engineers, engineers and policy makers need to be familiar with the science, but they need to do their own jobs and let the scientists do what scientists do.

    And, note that planners and engineers use many safety factors that do not have physical meaning. They can do that because it meets their needs. It is how engineered systems are planned and designed. However, it is not how science is done.

    Comment by Aaron Lewis — 27 Oct 2007 @ 5:10 PM

  41. Wayne #38
    nice catch. I gave the wrong URL, try,
    http://www.jpl.nasa.gov/news/news.cfm?release=2007-112
    for the updated article. For the record the ice is gone and no one should dispute that. My only reason for bringing this article up is to find AGW literature regarding its effects on wind.

    [Response: Try this, and subsequent papers, Miller et al, 2006 for instance. It's not certain, but there are indications that one should expect a more positive phase AO. With respect to the paper talked about in the release you link, read the full paper: http://www.agu.org/pubs/crossref/2007.../2007GL031138.shtml - you will note that the dynamic impact of the wind is not the exclusive cause of this year's anomaly. As indeed you would expect, especially since the winds were even more favorable for ice export in the early 90's. It wasn't as warm back then.... - gavin]

    Comment by Ellis — 27 Oct 2007 @ 5:59 PM

  42. Further to my post #39 (which was actually referring to #29 and not #21 as stated, sorry):

    As an example of what I meant, compare Ken Caldeira’s op-ed with the comment he posted on Realclimate. I much preferred his comment here to his op-ed, but his comment here didn’t disclose any less than his op-ed did – quite the reverse, in fact. The point is that his comment here is far less prone to being misinterpreted and misrepresented than his op-ed is, and that was also my concern about the interview with Gerard Roe.

    Comment by Dave Rado — 27 Oct 2007 @ 6:39 PM

  43. Before I dive in, Thank you Gavin.

    Comment by Ellis — 27 Oct 2007 @ 6:44 PM

  44. Good post and comments, and it’s very timely to see this topic raised again. The long upper tail is deeply worrying, particularly as there seems to be no let up in the rate of increase in the concentration of CO2. To my mind, there is little prospect of CO2 peaking at less than 600 ppmv, which is well over the ‘targets’, and the targets themselves may already be above what is reasonably live-able with.

    Regarding the possibility of an ice-free (summer) Arctic, I’d still be interested to see some modelling of the submarine ice melt, which could be considerable but spatially confused, setting up all sorts of changes in the deeper ocean circulation. How these changes might feed into the Atlantic (mainly), I don’t know, but I don’t doubt we’ll find out soon enough. One possibility is that the deep melt is brought to the surface somehow, in which case the surface waters actually get colder again, leading to much greater summer ice rather than less. No doubt the ‘skeptics’ would be pleased by such an ‘anomoly’, using it as further evidence that the climate models are wrong. Another possibility might be a slowing of deep circulation (not sure how much there is, mind), in which case the opposite occurs, and the surface waters heat up even faster, leading to yet more rapid surface melt, smaller winter ice volumes and so on.

    Comment by Nick O. — 27 Oct 2007 @ 7:15 PM

  45. In Ref 30 it’s stated that: “The climate models did not predict last summer’s ice retreat or anything like it in the near future.”

    I disagree, check out the following:

    http://www.realclimate.org/index.php/archives/2007/01/arctic-sea-ice-decline-in-the-21st-century/langswitch_lang/sp#more-391

    This clearly shows some potential for rapid retreat, not quite as soon as now but certainly in the ‘near future’.

    Comment by Phil. Felton — 27 Oct 2007 @ 7:45 PM

  46. I admit to a limited knowledge of glaciology. I am also confused by this information that seems to be at odds with the “ice melting everywhere” theory. NASA information, any help is appreciated. Thanks.
    http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17257

    Comment by petefontana — 27 Oct 2007 @ 8:13 PM

  47. Re #41: On a conceptual level, I think a lot of people imagine that as the atmosphere warms that somehow the climate system will respond in place. As demonstrated in the abstract pasted below, we are pushing on the climate system and it is indeed moving. That distance works out to about 200 miles for each hemisphere, BTW, so this is not a small change. As the tropics expand, the poleward portions of the climate system come under pressure. Are we playing dominos blindfolded?

    Recent widening of the tropical belt: Evidence from tropopause observations

    Dian J. Seidel (NOAA, Air Resources Laboratory, Silver Spring, Maryland, USA)

    William J. Randel (NCAR, Atmospheric Chemistry Division, Boulder, Colorado, USA)

    Radiosonde measurements and reanalysis data are used to examine long-term changes in tropopause behavior in the subtropics. Tropopause heights in the subtropics exhibit a bimodal distribution, with maxima in occurrence frequency above 15 km (characteristic of the tropical tropopause) and below 13 km (typical of the extratropical tropopause). Both the radiosonde and reanalysis data show that the frequency of occurrence of high tropopause days in the subtropics of both hemispheres has systematically increased during the past few decades, so that tropical characteristics occur more frequently in recent years. This behavior is consistent with a widening of the tropical belt, and the data indicate an expansion of about 5–8° latitude during 1979–2005.

    Comment by Steve Bloom — 27 Oct 2007 @ 8:47 PM

  48. Dave (39), sorry if I misinterpreted your post.

    Comment by Rod B — 27 Oct 2007 @ 8:52 PM

  49. WHOAS at MBLWHOI Library:
    Variation in Serripes groenlandicus …
    Interannual variation in growth corresponded to the Arctic Climate Regime Index (ACRI), with high growth rates during the positive ACRI phase characterized …
    https://darchive.mblwhoilibrary.org/handle/1912/1232

    Comment by Hank Roberts — 27 Oct 2007 @ 9:43 PM

  50. Ellis, the more commonly used terms in climate seem to be “Arctic Oscillation” or “Arctic Annular Mode” — try Scholar:
    http://scholar.google.com/scholar?num=100&hl=en&lr=&newwindow=1&safe=off&scoring=r&q=Arctic+oscillation+clockwise+wind&as_ylo=2007

    Comment by Hank Roberts — 27 Oct 2007 @ 9:49 PM

  51. Hi,
    I am an alternative planners for electricity and energy utilization, Indonesia. I may say the only one. As a national planner, I am looking for formal and strongest identification problem, such as from consumers to cooperatives.

    Please look a great case of the captive market of combined heat and power (CHP) as vizualized by American Institute of Physics:
    http://www.aip.org/pt/vol-53/iss-11/captions/p29box2.html

    My remark under uncertainty and certainty remains, placing Cooperative CHP between public electricity and private industry. The benefits are
    IEC can be implemented for public electricity
    ISO can be implemented for private industry
    ITU can be implemented for cooperative CHP.

    The reverse of Cooperative CHP is Multi Purpose Dam:

    http://www.ia-itb.com/node/445

    We faced parallel danger or the certainty of uncertainty.

    Keywords: reliability engineering, interdependency, intellectual property

    Comment by Tjahjokartiko Gondokusumo — 27 Oct 2007 @ 9:58 PM

  52. Re. #46, in the interior of polar continents and very large islands (Antarctica, Greenland), increased precipitation as snow resulting from the increase in warmer air’s capacity to hold moisture, results in an increase in ice mass balance. But at the periphery of Antarctica and Greenland, the ice is melting rapidly.

    In addition, in the case of Antarctica, the ocean currents there buffer it to a large extent, as a result of which increased heat from global warming is not carried there from the tropics at anything like the rate that it is carried to the Arctic. And ozone depletion has also tended to cool the Antarctic. For more on this see here).

    The trend for both the observed and modelled overall ice mass balance is very rapidly negative in the case of Greenland and slightly negative in the case of Antarctica – although the Antarctic peninsula is one of the most rapidly warming and melting regions on earth, and although there are serious worries that some very large ice shelves in Antarctica are prone to extremely rapid collapse followed by melting, as has already happened in the case of Larsen B, an ice shelf approximately the size of Luxembourg which collapsed in only 3 days – and that this phenomenon could possibly have a big impact in rates of sea level rise in the coming century.

    Outside of Greenland and Antarctica, glaciers are indeed melting almost everywhere, at an extremely rapid rate. The overall global glacier mass balance trend is shown on the National Snow and Ice Data Center (NDIS) graph here. The NDIS website is well worth exploring.

    With respect to of glacier loss outside of the Greenland and Antarctica, the biggest worry is not so much the effect on sea level (although they too will affect sea level), but more seriously, the severe permanent droughts that will result. Many hundreds of millions of people (and huge ecosystems) rely for their water on the annual glacier summer melts that in many cases may cease during the next 50-100 years, as mountain glaciers start to disappear.

    Comment by Dave Rado — 27 Oct 2007 @ 10:23 PM

  53. #45:

    Yes. Cecilia Bitz’s group’s sea ice projections actually don’t look too bad. Here’s her Fig 2 updated with the Sept’07 sea ice extent. The general shape of the 2007 decline is well replicated in Run 5; it just has it a touch later (about 2013). Modelling conservatism, perhaps?

    For now, the large Beaufort Sea – East Siberian Sea SST anomaly continues to decay. Refreeze cannot be far off. Await next summer with interest…

    Comment by GlenFergus — 27 Oct 2007 @ 10:49 PM

  54. Re: 46

    How does the information in that article contradict the “ice melting everywhere” theory? Of course no such theory exists, or if it does perhaps you should provide a link. The current models acknowledge that some glaciers may grow (very few are).

    From your link:
    “In some instances, bright red spots or streaks along the edge of the continent show where icebergs calved or ice shelves disintegrated, meaning the satellite began seeing warmer ocean water where there had previously been ice.”

    I guess the ice is melting in the antartic, at the edges — as expected.

    Comment by Kevin — 27 Oct 2007 @ 11:31 PM

  55. RE #18 & “as changes get larger, the sensitivity may grow or shrink”

    I’m not sure if I’m getting this right, but from what I understand from earlier discussions is that the sensitivity re how much warming happens given a certain increase in CO2 (if we could know exactly what it is) stays the same or decreases somewhat with increased CO2e input. I think there is a log relationship, but for our considerations of doubling CO2 it looks fairly linear. I think it’s more a matter of the physics of the situation, and the sky is just too big a lab and the experiment still ongoing to get exact results and there are these pesky “internal” feedbacks — such as water vapor and clouds.* [*I'm not sure, but I think this is what "f" refers to, and not the "external" feedbacks I mention below.]

    The point I was trying (but perhaps failing) to make in #11 was that there are greater uncertainties than that of the CO2/warming sensitivity regarding how nature would respond to the warming (in many many ways) — nature’s various “sensitivities” both to the warming and to concomitant factors (methane from melting permafrost & hydrates; CO2 reaching optimal levels for plants, then becoming more a pollutant, etc), which makes the amount of CO2 released into (or not absorbed from) the atmosphere uncertain. Maybe not right now, but in the future.

    So while the sensitivity of CO2/warming may be an important (though somewhat uncertain) matter, so too is how sensitive nature is in emitting GHGs in response to the warming (& to the concomitant GW effects), and this it seems is a lot more uncertain and has a lot more potential for danger…like some sleeping monster we keep poking.

    So even if the CO2/warming sensitivity is low, if nature’s sensitivity to the warming is high & a whole lot of GHGs get released, then the warming might go really high, perhaps higher than if the C02/warming sensitivity were higher, but nature’s sensitivity (net GHG emissions in response to the warming) were lower.

    Someone please let me know if I’m getting this wrong.

    Comment by Lynn Vincentnathan — 28 Oct 2007 @ 12:21 AM

  56. Re #20:

    • plants in a hotter climate are darker

    Karen-

    I don’t mean to pick. But where did you get that from? As a general rule, leaves are actually darker when there is less sunlight (shade, higher latitudes and lower altitude). Many plants will adjust their color (over time) to the amount of sunlight by changing leaf color (assuming they are otherwise healthy).

    As far as CO2 fertilization, plants can only use so much CO2 (the limits of minerals, water, nitrates and sunlight tend to be more important for most plant ecosystems).

    But an interesting side-effect is that the leaves need to respire LESS – which means the plant loses less water which means that more CO2 makes the plants more drought tolerant. This also increases soil moisture and reduces plant take up of rainfall. The latter along with increasing glacier melt has led to river flow increases – particularly in China and India which has led to more food production – and unfortunately a large increase in population – and well… a large increase in human suffering in the coming decades.

    Comment by Robin Johnson — 28 Oct 2007 @ 12:32 AM

  57. Please, please show me just one quantitative paper where a doubling of atmospheric CO2 produces a temperature change of X or Y degrees, even if it’s negative. All I have been able to find is left-overs in GCMs which have been blithely ascribed to CO2, plus a bit of spectroscopy, lab style, that I was taught in the 60s. Several of us have been looking, but nowhere can we find a defining paper that is quantitative, that shows where in the atmosphere the temperature change occurs and what its magnitude, sign and uncertainty are. No need to reference anything from IPCC, it has been searched for a nill result.

    Since this is a foundation stone question for anthropogenic global warming, we think that someone ought to have made an attempt to confirm the modelled hypotheses.

    No silly answers please. This is a serious question.

    [Response: It is one we have dealt with many times before: e.g. here and here. - gavin]

    Comment by Geoff Sherrington — 28 Oct 2007 @ 1:48 AM

  58. #34 Timothy, #27 Pascal, #19 Karen

    Thank you for your answers. In fact, “empirical” evaluation of each positive or negative feedback contributing to climate sensitivity was not my point here. I’ve now read carefully the Roe and Baker paper, so I better undestand their method and purpose (at least, I hope). They demonstrate or explain more precisely the asmytric relationship between f and S in present climate models (so, they use mean or better estimates of these models without any opinion about the quality of these estimates). There’s no real progress in our evaluation of climate sensitivity, rather the demonstration that real progress will be very difficut to reach (worse even, the range should enlarge as we include more and more parameters for evaluation of f, so more and more uncertainty because each new parameter will have its own distribution of probability).

    Concerning the CS from an empirical /physical perspective, there would be much more to say. For example, Spencer et al 2007 analysis of recent and precise climatologies suggests that the iris effect is not dead, after all, and the order of magnitude of the negative feedback (-6W/m2 TOA for warm tropical events) is interesting. Fortunately, the scientific research is still open and all hypothesis need to be carefully adressed.

    Comment by Charles Muller — 28 Oct 2007 @ 2:26 AM

  59. Dave Rado #52, thanks. That’s a very useful and detailed response. I do have a couple of observations. Some prominent individuals have suggested that the disintegration of the West Antarctic Ice Sheet is part of an overall climate “tipping point.” I have heard that is supposed to be reached by December 6, 2015.
    The whole positive/negative AO AAO thing seems highly variable. I’ve looked at those charts, too. And the increasing cold at the poles seems strange. Is a catastrophic double polar meltdown really a certainty? Let’s hope not.

    Towards the lower latitudes, I certainly hope hundreds of millions of people are not overly dependant on glacier fed water supplies. If they are, was this ever a good idea?

    Comment by petefontana — 28 Oct 2007 @ 3:10 AM

  60. Nick 44. That was my thought too. With the Antarctic sea ice maximum observed this year I wondered if it was due to the sub-surface melt lakes discharging fresh super-chilled water out under the ice sheets. This then rises to the sea surface enhancing the extent of freezing pack ice. The extent of pack ice could perhaps be correlated to the ice mass loss. Maybe?

    Comment by Nigel Williams — 28 Oct 2007 @ 4:03 AM

  61. The article above says:

    For example, 450 ppm is an oft-cited threshold since this keeps deltaT below 2°C using standard climate sensitivities. But the skewed nature of the distribution of possible sensitivities means that it is much more likely that 450 ppm will give us more than 4.5°C of global warming rather than less than 2°.

    If 2 degrees is the most likely value (for 450ppm) then the above statement doesn’t seem to make sense. Surely there would be approx 50% probability of less than 2 degrees and a rather lower probability for more than 4.5.

    Was the last bit supposed to read “less than zero degrees”?

    Comment by SCM — 28 Oct 2007 @ 5:09 AM

  62. Re #56

    John Harte discussed a shift to darker plants at the China US Climate Change forum in Berkeley. Here is an explanation for the public. He said — there or elsewhere — that the ice age ended so quickly in part because spruce trees chased the ice away — ice disappeared to be replaced by spruce trees which warmed the area which caused more ice to disappear.

    Harte warmed an area in the Rockies to see what happens, and found sagebrush replacing leafy perennials.

    The heated meadow began to look different-more desertlike than pastoral-but the changes weren’t just aesthetic. Sagebrush is much less reflective than the flowers; where the light-colored flowers once reflected much of the sun’s energy back into space, sagebrush, with its dark bark, absorbed it. So as the sagebrush spread, the meadow began to grow even warmer.

    …Sagebrush, by comparison [with the flowers], is less active at photosynthesis and it produces far less plant material each year. As the sagebrush spread, Harte began to observe a disturbing trend: The carbon that was bound up in the soil continued to be released through the work of microbes, but now it was no longer being replaced.

    Plants of one species may change color with the amount of sunlight, but there is also a shift in species with temperature.

    Plants may leave more water in the soil with increased CO2 in areas where temperature does not rise. The expected increase in temperature will more than compensate for the extra CO2 and dry out the soil.

    Also, as Harte showed, species selected for a warmer climate sequester less carbon, so the amount of carbon stored in biota will decrease, at least in Alpine regions.

    Comment by Karen Street — 28 Oct 2007 @ 8:58 AM

  63. #59 & “I certainly hope hundreds of millions of people are not overly dependant on glacier fed water supplies”

    That’s about right. A large chunk of humanity is dependent on glacier melt (also snowpack melt — e.g., I think in the U.S. west). This includes among other peoples 40% of India’s and China’s populations, which comes to 500 million people, but doesn’t include the many millions of glacier-dependent people elsewere.

    But rather than suggest is was a bad idea to become dependent on the glacier and snowpack melt cycles, I think it was a bad idea to become dependent on fossil fuels, and a bad idea to still be so addicted to them right now, when I’m sure we could reduced our consumption worldwide by at least 70% without much harm to the economy. Tho it would take years and decades to make the transition. And we really should have started that back in the 1970s during the 1st energy crunch, then ratcheted way up by the late 1980s, when the world became aware of the GW dangers. Then we’d nearly be there by now (and the scientists would be even more uncertain about sensitivity & other aspects of GW :)). The tech is there; for instance, passive solar has been known about and practiced for over 2000 years — but not by profligate us!

    RE “double polar meltdown” I’ve never heard that (and I suppose it wouldn’t happen for many many centuries, if at all it does happen). Perhaps you’re equating the West Antarctic Ice Sheet (which IS melting and disintegrating) with the whole of Antarctica — a much larger area, much of which is not yet so affected by GW.

    Comment by Lynn Vincentnathan — 28 Oct 2007 @ 8:59 AM

  64. So what exactly do Roe & Baker include in “f” feedbacks? (I don’t have access to the article.) Is it what I think — water vapor and clouds. Or does it include GHG releases from melting permafrost and hydrates, and other such factors?

    I can’t imagine it including the “AC” feedback loop — people buying and using air conditioners a lot more in a warming climate, mainly using coal-powered electricity to run them, causing greater CO2 emissions, causing greater warming, causing still greater AC use. Of course, this would be offset somewhat by the negative feedback of less gas and electric heater use.

    Comment by Lynn Vincentnathan — 28 Oct 2007 @ 9:10 AM

  65. #62: Ah. I see what you were saying. Certainly, taiga and heavy brush is going to absorb more light than pathetic tundra plants and grasses. And that’s what we expect to happen as things warm up. Obviously, I agree with that.

    Robin

    Comment by Robin Johnson — 28 Oct 2007 @ 9:54 AM

  66. Petefontana, you wrote:

    > West Antarctic Ice Sheet is part of an overall climate
    > “tipping point.” I have heard that is supposed to be
    > reached by December 6, 2015.

    It seems you are the one to put that on the Internet for the first time. Where did this story reach your ears? It looks like a joke missing the punch line.

    > the increasing cold at the poles

    What “increasing cold” do you mean? What’s your source?

    > seems strange.

    Why? Compared to what?

    The “guy I heard talking in a bar” cite is funny, the first time.

    Comment by Hank Roberts — 28 Oct 2007 @ 10:25 AM

  67. Robin Johnson (#56) wrote:

    But an interesting side-effect is that the leaves need to respire LESS – which means the plant loses less water which means that more CO2 makes the plants more drought tolerant. This also increases soil moisture and reduces plant take up of rainfall.

    Yes, in fact we have seen this in the paleoclimate record and it has helped us identify the levels of carbon dioxide in earlier climates. But how quickly they will adapt depends upon the species of plant. With some plants it has to evolve. In others it is developmental. But higher levels of carbon dioxide may also decrease nutritional value.

    The Paleoclimate Record

    One of the ways that we can measure the level of carbon dioxide in earlier periods is by measuring the size of the stomata and and their number. Fewer and smaller stomata imply higher levels of carbon dioxide.

    Waiting for an Evolutionary Adaptation

    The experiments to date indicate that some plants do not automatically adjust themselves to increased levels of carbon dioxide. It has to evolve.

    For one of the studies showing that some would have to evolve this adaptation, please see:

    Effect of Elevated CO2 on Stomatal Size and Distribution in Perennial Ryegrass (html abstract only – despite the file extension)
    G. J. A. Ryle and J. Stanley
    Annals of Botany 69: 563-565, 1992
    http://aob.oxfordjournals.org/cgi/reprint/69/6/563.pdf

    Not that difficult on evolutionary scales I would presume. Several different species of ice fish have evolved antifreeze independently of one another and even to the point that they have made their blood less viscous by losing the ability form red cells as mere water has the capacity to carry sufficient oxygen at lower temperatures.

    This would have to have evolved since the last hot house and probably evolved in previous eras as well. Once they lose the ability to form red cells, the genes responsible for red blood cells mutate to the point that they will be unable to evolve back – as this is a great deal more complex than decreasing the size or number of stomatas. These fish would likely go extinct even if climate change were particularly slow – once the temperature of the Arctic and Antarctic Oceans rise above the level that the water is unable to carry sufficient oxygen.

    However, there are many plants we won’t see adapt in this fashion any time soon. Unlike our circulatory systems which adapt to thinner air at higher altitudes, the ability to developmentally adapt to higher concentrations of CO2 just isn’t there.

    Developmental Adaptation

    Others plants show different developmental strategies, increasing size (stomatal index), number (density) or epidermal cells size of stomatas. These are part of their developmental programming, similar to our adjusting the number of capillaries at different altitudes – probably for the same reason as this would result in their ability to better adapt to different altitudes, increasing the range of the species or subspecies.

    Please see:

    Stomatal Characteristics of Four Native Herbs Following Exposure to Elevated CO2 (html abstract only)
    Rachel Ferris and Gail Taylor
    Annals of Botany 73: 447-453, 1994
    http://aob.oxfordjournals.org/cgi/content/abstract/73/4/447

    Lower Nutritional Value

    Another thing to keep in mind: some plants will simply grow more quickly. However, this isn’t necessarily a good thing: in experiments performed by the Chinese with rice and wheat it nearly eliminates any gains with rice that would result from “CO2 fertilization,” and results in losses with wheat. These are main staples for much of the world’s population.

    Please see:

    Rising carbon dioxide could make crops less nutritious (Non-tech.)
    Jia Hepeng
    4 March 2005
    http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=1969&language=1

    Responses of rice and winter wheat to free-air CO2 enrichment (China FACE) at rice/wheat rotation system (abstract)
    Ma, Hongliang et al
    Plant and Soil, Volume 294, Numbers 1-2, May 2007 , pp. 137-146(10)
    http://www.ingentaconnect.com/content/klu/plso/2007/00000294/F0020001/00009241

    However, lanthanum (the element with atomic number 57) may be used to slow the growth of rice and thereby regain some of the nutritional value.

    Please see:

    Influence of Lanthanum on Phosphorus Uptake and Its Chemical Fractions in Rice Crop (Oryza Sativa) [translated abstract]
    Xie Zubin, et al
    [A Chinese periodical, the name of which is untranslated](2003)
    http://scholar.ilib.cn/Abstract.aspx?A=zgxtxb-e200302021

    Comment by Timothy Chase — 28 Oct 2007 @ 11:14 AM

  68. Re #67: No need to provide information on CO2 fertilization. I’m a plant growing aquaticist – who does NOT use CO2 fertilization but whose tank is overrun with plants anyway – mainly because I use a wet-dry filtered reef tank with a closed top where the water is mixed with air in large quantities in the sump keeping the amount of CO2 and O2 at optimal levels. Stagnant plant tanks (the usual kind) lose CO2 and O2 because the water is warm with little mixing. As I pointed out in my previous post, CO2 is not a limiting factor for most plants (vines apparently benefit).

    While I am deathly concerned about Global Warming and its destructive effects – and quite frankly I think we’re fubar, ecosystems change VERY rapidly over decadal time scales. Until the 1940s, the DOMINANT tree in the Eastern US was the Chestnut. They are all gone due to a fungal disease. The Eastern US is still heavily forested. Forests in the African savannah region come and go quickly. Plants are just waiting to take advantage of a changed ecosystems. Drier conditions in many areas will turn forests into grasslands and wetter, warmer conditions will change grasslands into forests. I’m not assuming all will be “well” – not at all. I suspect things will be *bad*.

    And its a fact that many non-crop plants DO use less water with higher CO2 (but the effect is not linear for obvious reasons). And evolution “happens” damn quickly despite the way its taught (or not taught) in schools – because the traits are ALREADY there waiting to be exploited. Developing traits those don’t exist in a plant genus or family is obviously harder and takes longer timescales.

    Comment by Robin Johnson — 28 Oct 2007 @ 1:04 PM

  69. Tjahjokartiko Gondokusumo (51) — There are at least two CHP reported upon in

    http://biopact.com

    which use biomass to produce bioenergy and either process heat or else electicity. For the one in the The Netherlands, on that site the search term biocoal should find the report. The other is on the German-Polish border and the process heat is used to heat nearby houses.

    People at Biopact are likely to prove quite helpful to you if you choose to contact them via their site.

    Comment by David B. Benson — 28 Oct 2007 @ 1:28 PM

  70. Charles Muller (#58) wrote:

    #34 Timothy, #27 Pascal, #19 Karen

    Thank you for your answers…

    Uncertainties: Additive or Canceling?

    Charles Muller (#58) wrote:

    There’s no real progress in our evaluation of climate sensitivity, rather the demonstration that real progress will be very difficut to reach (worse even, the range should enlarge as we include more and more parameters for evaluation of f, so more and more uncertainty because each new parameter will have its own distribution of probability).

    According to them there has been no progress.

    Annan and Hargreaves (2006) argue that Bayesian analysis has narrowed the range of Charney climate sensitivity considerably – and that it is about 3 C. In part this is due to the climate record. However, studies as far back as the 1960s have shown that an estimated Charney climate sensitivity of about 3 C seems about right, so I guess you could say that there has been no progress. What Gerard Roe and Marcia Baker specifically reference is th 5700 multi-ensemble by climateprediction.net which is notorious for its wide spread of values. However, they also cite a variety of studies in which the upper or lower limits are wide – where some are empirical. I don’t know which ones.

    While Annan and Hargreaves gave an upper limit (at 5%) of 4.5 C, Annan suggests that this is actually being generous with the uncertainty in his blog – not that this matters so much until the technical paper comes out which demonstrates a narrower range. But for me, the question is whether Bayesian analysis may narrow the range. Annan suggests it can, in a way that is somewhat analogous to the number of surface stations increasing the accuracy of our estimation of the global average temperature and its trendline.

    The Iris Effect

    Charles Muller (#58) wrote:

    Concerning the CS from an empirical /physical perspective, there would be much more to say. For example, Spencer et al 2007 analysis of recent and precise climatologies suggests that the iris effect is not dead, after all, and the order of magnitude of the negative feedback (-6W/m2 TOA for warm tropical events) is interesting. Fortunately, the scientific research is still open and all hypothesis need to be carefully adressed.

    Well, it is a different sort of iris effect from that which was originally proposed: the pupil becomes more dilated with increased infrared rather than more constricted. Or should we now call it the retina effect? But of course retinas don’t shrink, do they? It was demonstrated that the tropical clouds which would be subject to the iris effect tend to increase the strength of the greenhouse effect, but the empirical study which you have cited demonstrates that these clouds become less common. Or is it possible that they become more spread out? I am thinking of the twilight effect where there is an invisible extension to clouds extending for tens of kilometers.

    May 3, 2007
    Widespread Twilight Zone Detected Around Clouds
    http://earthobservatory.nasa.gov/Newsroom/NasaNews/2007/2007050324883.html

    On the twilight zone between clouds and aerosols (abstract)
    Ilan Koren, et al
    18 April 2007
    Geophysical Research Letters, Vol. 34, L08805, doi:10.1029/2007GL029253, 2007
    http://www.agu.org/pubs/crossref/2007/2007GL029253.shtml

    This might be a way of explaining the results which show a clear sky super greenhouse effect in which downwelling thermal radiation from the atmosphere increases more rapidly in the tropics than upwelling thermal radiation at sea surface temperatures (SSTs) above 300 K, occuring over 52 % of the tropics between 20 N and 20 S between the years of 1985 to 1989.

    Please see:

    Direct Radiometric Observations of the Water Vapor Greenhouse Effect Over the Equatorial Pacific Ocean
    Francisco P. J. Valero, et al
    Science Vol 275 Mar 1997, 1773-1776
    http://www.sciencemag.org/cgi/content/full/275/5307/1773

    It is after all clouds in the tropics which show the “negative feedback” of “fewer” clouds. And I suppose if we aren’t talking about the twilight effect, then the negative feedback won’t be that negative if the clear sky greenhouse effect is becoming stronger with higher temperatures. So in this sense the inverse “iris effect” is quite dead to the extent that it might be regarded as contributing a significant negative feedback in the tropics. The form that Spencer (2007) brings up would appear to be overwhelmed by the super greenhouse effect which we have been aware of since 1997.

    Are the Models Improving?

    I would also keep in mind the fact that the more physics we include in the models, the more accurate they become — at least in terms of being able to model the climate system. Gavin Schmidt has said as much and I would presume that he would know. Given that models have been improving in their ability to model processes, I personally find it difficult to believe that, at least in terms of a Bayesian analysis, the models themselves aren’t doing better in terms of their ability to identify climate sensitivity by applying first principles to our climate system.

    I would also keep in mind the fact that we are only speaking of the short-term Charney Climate Sensitivity, and the long-term climate sensitivity is presumably going to be about twice that – due to ice sheet loss and the like.

    Please see:

    Hansen, J., Mki. Sato, P. Kharecha, G. Russell, D.W. Lea, and M. Siddall, 2007: Climate change and trace gases. Phil. Trans. Royal. Soc. A, 365, 1925-1954, doi:10.1098/rsta.2007.2052
    http://pubs.giss.nasa.gov/abstracts/2007/Hansen_etal_2.html

    But I suppose this may involve the longer tail which people are worried about. Then again, if Roe and Baker are including multiple studies, this might also explain some of the uncertainty which they are seeing as they could be conflating short-term (~3 C) and long-term (~6 C) climate sensitivities. Hansen (2007) suggests that the climate records involving Antarctica do a fairly good job of narrowing the range on the long-term climate sensitivity – and studies of present day climate change would remain silent for the most part as the long-term feedback has only begun to kick in.

    The big question for Hansen is of course how quickly these long-term feedbacks will take to manifest themselves, and given what we are now seeing as well as the paleoclimate record itself, it seem that the answer is sooner rather than later. Especially since black carbon wasn’t as much of an issue in previous instances of global warming and is now becoming an issue again as the result of economic development in China. Of course we may also want to keep in mind the higher rates of carbon emissions since 2000 – which weren’t included in IPPC R4 projections. If I remember correctly, they’ve tripled.

    Anyway, hope this helped…

    Comment by Timothy Chase — 28 Oct 2007 @ 1:37 PM

  71. Re #61
    SCM, all the group are saying is that you have to consider the actual probability distribution, and for ill-behaved distributions it is quite possible to have more probability above 2x the mode than below the mode. Consider the Pareto distribution, which is used to fit percentile wealth vs percentile population as an example.

    Comment by Ray Ladbury — 28 Oct 2007 @ 1:48 PM

  72. #70 Timothy

    Thank you for the references.

    The 2,1-4,4 °C range of IPCC 2007 (with 3°C as best estimate) is equilibrium (long term) sensitivity. Transient climate response for 2xCO2 is rather 1,0-2,6°C. So, I don’t know what you mean exactly when you suggest a long-term climate sensitivity twice more important.

    Comment by Charles Muller — 28 Oct 2007 @ 2:05 PM

  73. Can I seek a clarification here? I understand that climate sensitivity is temperature response to change in atmosphere CO2 concentration, not a response to change to man-made CO2 emission. So feedbacks like reduced ocean capacity, changes due to landuse etc. might effect our ability to predict future CO2 levels for a given anthropogenic input, but they are irrelevant to the sensitivity of T to actual CO2 concentration. From the straight physics, surely the only feedbacks that affect the sensitivity are albedo, cloud effect (both positive/negative) and water vapour? Any others? Correct me if I am wrong too, but I thought GCMs were calculating T directly rather than parametizing through S? Ie I would expect S to output of a GCM not an input?

    Comment by Phil Scadden — 28 Oct 2007 @ 3:32 PM

  74. Charles Muller (#72) wrote:

    #70 Timothy

    Thank you for the references.

    The 2,1-4,4 °C range of IPCC 2007 (with 3°C as best estimate) is equilibrium (long term) sensitivity. Transient climate response for 2xCO2 is rather 1,0-2,6°C. So, I don’t know what you mean exactly when you suggest a long-term climate sensitivity twice more important.

    I didn’t say twice as important – as that would be a normative issue. Is what happens as the result of slow feedback important? Well, I guess it depends upon your standards. But in terms of the rise in temperature it would seem to be twice as high.

    But why?

    Essentially Charney climate sensitivity is calculated only with the fast feedbacks: water vapor, sea ice, etc. What it ignores are the slow feedbacks from the ice sheets and the carbon cycle itself — as it treates both as boundary conditions. For example, it treates ice sheets as a boundary condition and therefore ignores the fact that over time the ice sheets respond, amplifying the effects our of anthropogenic pulse of carbon dioxide.

    Likewise, when treating carbon dioxide simply as a forcing rather than our anthropogenic greenhouse gas emissions, it omits the fact that it is a pulse which may later be subject to feedback from the carbon cycle itself — which will amplify the greenhouse effect of the original pulse and likewise the effects of changes to the ice sheets.

    Now what do we mean by the slow feedbacks being “transient”?

    Pretend for a moment that we double the amount of carbon dioxide with our emissions. Seems rather likely to me, actually. First doubling. In the shortrun this raises the temperature best estimate 3 C. Afterwards the ice sheets melt. To keep things simple, we will say that all of the ice sheets melt and that they are responsible for all the slow feedback, but this does nothing more than double the effects upon temperature of the original pulse. Now we are at 6 C.

    By transient does this mean that as soon as the ice sheets are gone we drop back to 3 C?

    “Yes” in terms of climate sensitivity but “no” in terms of temperature.

    Yes in the sense that if we double the CO2 again this will simply bring us up to 9 C. No in the sense that simply keeping the CO2 at the first doubling will not cause the temperature to drop back down to 3 C. The climate sensitivity may very well be transient (dropping from 6 C per doubling down to 3 C per doubling after the ice sheets are gone), but this does not mean that whatever degrees we gain while it exists are suddenly lost any more than that the ice sheets will suddenly reappear once they have melted. Once the ice sheets are gone, they will be gone for a very long time. While they are gone for how ever many millenia the climate system will be absorbing more sunlight, and more thermal radiation will be produced. The “transient” nature of the slow feedbacks in no way changes this.

    Anyway, that is my understanding of the treatement of this issue in:

    Hansen, J., Mki. Sato, P. Kharecha, G. Russell, D.W. Lea, and M. Siddall, 2007: Climate change and trace gases. Phil. Trans. Royal. Soc. A, 365, 1925-1954, doi:10.1098/rsta.2007.2052
    http://pubs.giss.nasa.gov/abstracts/2007/Hansen_etal_2.html
    pg. 1944

    To what extent does the IPCC treate this issue?

    I honestly do know. However, we do know how they have dealt with the rise in sea level – and they limit their projections to the first century – as a steadfast rule, I believe. This would suggest to me that they aren’t really dealing with the issue of the “constant boundary conditions” for Charney-type analysis changing as a form of slow feedback. However, I believe the climatologists here might be in a better position to say.

    Comment by Timothy Chase — 28 Oct 2007 @ 3:48 PM

  75. Phil Scadden (#73) wrote:

    Can I seek a clarification here? I understand that climate sensitivity is temperature response to change in atmosphere CO2 concentration, not a response to change to man-made CO2 emission. So feedbacks like reduced ocean capacity, changes due to landuse etc. might effect our ability to predict future CO2 levels for a given anthropogenic input, but they are irrelevant to the sensitivity of T to actual CO2 concentration.

    So you would think.

    Certainly in terms of the underlying physics it is irrelevant whether it comes from us or various feedbacks from the carbon cycle. However, in terms of the fast-feedback Charney analysis, changes in CO2 is treated simply as a forcing being applied from to system from “outside” of the climate system, and as a forcing it is not viewed as feedback – at least according to Hansen (2007) – see above.

    But why take his word for for it? This is after all the fellow who if given 50 cm will take 5 m.

    So decided to check with the IPCC itself. Apparently he’s right.

    Please see:

    The coupled climate carbon cycle intercomparison project (C4MIP) will permit the assessment of model sensitivity of the carbon cycle to global temperature change. The carbon cycle feedback is potentially important to 21st century climate projections, but is not conventionally included in the climate sensitivity as it is not a fast feedback.

    IPCC Working Group I – Workshop on Climate Sensitivity, Workshop Report
    École Normale Supérieure, Paris, France
    26–29 July, 2004
    pg 11

    Comment by Timothy Chase — 28 Oct 2007 @ 5:51 PM

  76. A few comments on some issues raised in comments (#1, #2, #7, #11, #15, #47, #52, #73) on the nature of “S”:

    (1)From the paper: “Climate consists of a set of highly coupled, tightly interacting physical processes.”

    Physical in the academic sense? If so, I think we want to include tightly coupled chemical and biological processes, in that case – for example, the chemical fate of atmospheric methane over time, the effects of increasing atmospheric CO2 on oceanic acid-base chemistry, and the response of the biological components of the carbon cycle to increased temperatures and a changing hydrologic cycle.

    (2)From the paper: “Because we are considering an equilibrium temperature rise, we consider only time-independent processes.”

    The transient responses are of great concern. The difference between a slow transition and a fast transition to a new equilibrium position has at least two important effects: the rate of sea-level rise due to the speed at which ice sheets melt, and carbon-cycle feedback effects including a melting Arctic permafrost and potential destabilization of oceanic methane hydrates. Others include the ability of the biota to respond to new circumstances in a timely manner (the extinction issue) and the rate of change of the hydrologic cycle (which are linked).

    (3) From the supporting perspective article: “All this would be very bad news if avoiding dangerous anthropogenic interference in the climate system required us to specify today a stabilization concentration of carbon dioxide (or equivalent) for which the risk of dangerous warming is acceptably low. Fortunately, we do not need to.”

    That seems to assume a large degree of human control over carbon-cycle feedback processes and the ability to stabilize at some future point. Sometimes, when a fire gets big enough you can’t put it out (for example, consider the wind-driven wildfires in Southern California). Then you have the ice sheet dynamics issue.

    (4) From the above post: “Annan and Hargreaves (2006) used a Bayesian statistical approach that combines information from both 20th century observations and from last glacial maximum data to produce an estimate of climate sensitivity that is much better constrained than by either set of observations alone.”

    What’s the main difference between the past few million years of the glacial-interglacial cycle and the present? It seems that it is that the net size of the active carbon pool has increased by a fair amount relative to the glacial-interglacial pool due to transfer of fossil carbon to the atmosphere, and hence slowly to the oceans. What I’m wondering is if our activities could actually be putting an end to the past few million years of the interglacial-glacial cycle and return to the conditions that existed around 4 million years ago?

    What if atmospheric CO2 accumulation starts accelerating due to natural chemical-biological feedbacks due to warming oceans and land masses? What if the IPCC “business-as-usual” scenario is a large underestimate of the rate of increase of atmospheric CO2? No change in the equilibrium sensitivity to 2X CO2, but the transient response could be pretty rough.

    (5) From the above post: “However, in our view, Allen and Frame’s discussion turns the precautionary principle on its head by implying that downward revision can always be done later, after more data are in. But a good adaptive strategy depends on nimble action and forward thinking. . .” Yes! Well put.

    Comment by Ike Solem — 28 Oct 2007 @ 6:30 PM

  77. Re. #59, petefontana:

    I certainly hope hundreds of millions of people are not overly dependant on glacier fed water supplies. If they are, was this ever a good idea?

    Those glaciers (and the summer melt water they supply) have been there for the entire existence of human civilisation, so you may as well ask whether human civilisation was ever a good idea.

    Lynn Vincentnathan wrote in #63:

    A large chunk of humanity is dependent on glacier melt (also snowpack melt — e.g., I think in the U.S. west). This includes among other peoples 40% of India’s and China’s populations, which comes to 500 million people, but doesn’t include the many millions of glacier-dependent people elsewere.

    All of the “Stans” (Pakistan, Uzbekistan, Turkmenistan, etc.) are also dependendant on glacier melt, as are most of the Andean countries in South America (e.g. see here , here and here).

    Comment by Dave Rado — 28 Oct 2007 @ 7:38 PM

  78. Re #58: “Spencer et al 2007 analysis of recent and precise climatologies suggests that the iris effect is not dead, after all.” While there seems to be mounting evidence that Spencer must have studied some field other than climatology, I doubt that it was necromancy. Embalming, maybe. :) How many times do Spencer and Christy have to be proven wrong before people like you stop uncritically quoting their results?

    The science involved with the “iris” idea being quite difficult for laypeople, whenever the subject comes up I tend to resort to asking how the glacial cycles (and paleoclimate generally) can be explained if there really is an effect that damps sensitivity to that extent. I’m still waiting for an answer.

    Comment by Steve Bloom — 28 Oct 2007 @ 8:37 PM

  79. Timothy @74

    “Now what do we mean by the slow feedbacks being “transient”?
    Pretend for a moment that we double the amount of carbon dioxide with our emissions. Seems rather likely to me, actually. First doubling. In the shortrun this raises the temperature best estimate 3 C. ”

    See Table 8.2, chap. 2, IPCC 2007 :
    http://ipcc-wg1.ucar.edu/wg1/wg1-report.html

    The mean transient climate response for 2xCO2 is something like 1,7 °C. That’s what you call fast feedbacks response (water vapour, lapse rate, nebulosity, etc.)

    But 3,2°C is the best estimate for equilibrium climate sensitivity (that is when the runs of models consider all the feedbacks).

    Some AOGCM models have been coupled with carbon cycle models, but I’ve not yet regained the exact references concerning this coupling and the results for the range of equilibrium CS.

    Comment by Charles Muller — 28 Oct 2007 @ 8:45 PM

  80. Re. the Roe and Baker paper, William Connolley is dubious.

    As William says in his post, it’ll be interesting to see what James Annan thinks about it (I imagine he’s working on a post about it).

    [Response:I asked Gerard Roe to respond to William's concern, which is about the assumption that f is Gaussian. I posted his response (comment #6 below William's blog entry), which ought to clear this up.--eric]

    Comment by Dave Rado — 28 Oct 2007 @ 9:17 PM

  81. During the Jurassic, CO2 concentrations were at least 2000ppm higher than they are now, and temperatures were about 10C higher. So how does a 70ppm rise in CO2 produce a 4.5C increase in temperature? The models are overestimating temperature rise by an order of magnitude.

    It is important to occasionally correlate computer models with the historical record, otherwise they produce nothing but GIGO.

    [Response: Huh? 4.5C is a high estimate for doubling CO2 (i.e. an extra 280 ppm). Plus estimates of anything from the Jurassic are highly uncertain. - gavin]

    Comment by Patrick Henry — 28 Oct 2007 @ 10:49 PM

  82. Eric;
    Pat Michaels seems perfectly certain the ENSO is decoupled from temperature trends , and constant even over geological deep time . It would be interesting to see if his publisher will accept feedback from RC-
    http://www.spectator.org/dsp_article.asp?art_id=12225
    “The Fires This Time
    The American Spectator
    Patrick J.Michaels 10/29/2007

    “Blame California’s mega-fires on global warming. Or at least that’s what Senate Majority Leader Harry Reid (D-NV) said last week in the Hill.

    Global warming affords endless opportunities to test glib hypotheses by politicians who have no training whatsoever in fields of which they claim pontifical knowledge. And Reid’s statement is easy to test…California’s big wildfires are, ironically, caused by excessive winter rains. The more it rains in the winter, the more vegetation grows, and the more there is to burn in the summer, which is invariably hot and dry.

    Some of the very wet years are caused by El Nino, a reversal of winds over the Pacific Ocean that has been going on every few years ever since there was a Pacific Ocean…People… will cite computer models predicting that El Ninos should become stronger or more frequent with global warming, but there are an awful lot of other models showing that they won’t change or that they might even lessen in frequency. The Nobel Prize-winning United Nations Intergovermental Panel on Climate Change says “There is no consistent indication of discernible future changes in ENSO [an acronym for El Nino] amplitude and frequency.”

    Comment by Russell Seitz — 29 Oct 2007 @ 12:13 AM

  83. Re Charles Muller (#79) on climate sensitiviy, transient climate response, and slow versus fast climate feedbacks (with a focus on the carbon cycle)

    Or “Will a doubling of CO2 raise the average temperature by 3 C or 6 C?”

    **

    Charles, what I will argue is that there are two equilibria that need to be considered: that resulting from the fast feedbacks and that which results from all feedbacks. For the most part, the IPCC is concerned only with the fast feedbacks – although I will note below where this is changing. The “transient climate response” and transient climate sensitivity still refer to the fast feedbacks, of course. But so does the equilibrium climate sensitivity, only after the forcing ceases, e.g., we quite raising CO2 concentrations with our emissions.

    The Meaning of Transient Climate Response

    Charles Muller (#79) wrote:

    See Table 8.2, chap. 2, IPCC 2007 :
    http://ipcc-wg1.ucar.edu/wg1/wg1-report.html

    The mean transient climate response for 2xCO2 is something like 1,7 °C. That’s what you call fast feedbacks response (water vapour, lapse rate, nebulosity, etc.)

    Different beast, then. I had inadvertently misused the term “transient climate response” given the term “transient.” In a sense, the higher climate sensitivity associated with the slow feedbacks are transient, but the transient response and equilibrium response both refer to the fast feedbacks, not the slow feedbacks.

    What is meant by the “Transient Climate Response”

    In the “transient climate response,” we still aren’t talking about positive feedback from the carbon cycle, but we aren’t exactly talking about a single pulse of additional carbon dioxide, either. To let people see what we are talking about, let’s go to 2001 since that is up on the web as a webpage:

    Climate Change 2001:
    Working Group I: The Scientific Basis
    http://www.grida.no/climate/ipcc_tar/wg1/345.htm

    As we raise the level of carbon dioxide by means of our emissions, the temperature rises. When we stop raising the level of carbon dioxide, the temperature continues to rise because it takes a while for the climate system to reach equilibrium. Partly this is due to the thermal inertia of the ocean, the fact that it takes while for the stratosphere to expand and then finally warm to its equilibrium level.

    For the moment, lets just go into the evolution of the stratosphere under an enhanced greenhouse effect – assuming a single pulse of carbon dioxide. The stratosphere first cools due to reduced longwave, then the surface and lower atmosphere rise in temperature, the troposphere expands and expands the stratosphere with it, further cooling the stratosphere. Then as the troposphere warms, more longwave escapes to the stratosphere, warming the stratosphere, although it will still be cooler at the end of the process than at the beginning.

    That takes time. So does the warming of the ocean, or for that matter, even the water vapor feedback as the increasing partial pressure water vapor is both a response to higher temperatures and a cause of higher temperatures – but can raise temperatures only against the thermal inertia of the ocean. As such, when emissions quit raising the temperature, it will still take a considerable amount of time for the system to reach equilibrium.

    Does the IPCC’s “Equilibrium Climate Sensitivity” Include All Feedbacks?

    Charles Muller (#79) wrote:

    But 3,2°C is the best estimate for equilibrium climate sensitivity (that is when the runs of models consider all the feedbacks).

    No, I am afraid not.

    Even at this point, the equilibrium is still one that is based on fast feedbacks, not the slow feedbacks involved in either the carbon cycle or ice sheets – as these would be assumed constant by the Charney analysis of climate sensitivity.

    This is most easily seen in AR2, but it still applies (more or less) to AR4 — as I will show shortly.

    For AR2, please see:

    2.3.3 Climate Sensitivity: Definition

    The term “climate sensitivity” refers to the steady-state increase in the global annual mean surface air temperature associated with a given global mean radiative forcing. It is standard practice to include only the fast feedback processes, including changes in water vapour, in the calculation of climate sensitivity, but to exclude possible induced changes in the concentrations of other greenhouse gases (as well as other slow feedback processes).

    An Introduction to Simple Climate Models used in the IPCC Second Assessment Report (1997), pg 12
    http://www.ipcc.ch/pub/IPCCTP.II(E).pdf

    But that was 1997.

    Preparing for AR4

    Let’s look at something a little later, something done in preperation for AR4 – plans testing the incorporation of the carbon cycle into climate models. It specifically states that climate sensitivity does not conventionally include carbon cycle feedback as it is “not a fast feedback.”

    Please see:

    The coupled climate carbon cycle intercomparison project (C4MIP) will permit the assessment of model sensitivity of the carbon cycle to global temperature change. The carbon cycle feedback is potentially important to 21st century climate projections, but is not conventionally included in the climate sensitivity as it is not a fast feedback.

    IPCC Working Group I – Workshop on Climate Sensitivity, Workshop Report
    École Normale Supérieure, Paris, France
    26–29 July, 2004
    pg 11

    Incidentally, the intercomparison project was completed – but we will get to that in a moment.

    Climate Sensitivity in the AR4 Glossary

    Looking at the glossary entry for “climate sensitivity” (which is too long to quote but the location of which is clearly identified in the table of contents) in AR4 WG1 (2007) suggests that nothing has changed in this regard.

    *

    Chapter 8 of WG1 AR4

    Looking at the Chapt 8 Executive Summary, we find that they are merely exploring the potential importance of carbon cycle feedbacks.

    Please see:

    Chapter 8, Executive Summary

    To explore the potential importance of carbon cycle feedbacks in the climate system, explicit treatment of the carbon cycle has been introduced in a few climate AOGCMs and some Earth System Models of Intermediate Complexity (EMICs).

    AR4WG1, Chapt 8 (2007), pg. 591

    *

    They are considering the addition of some components of the carbon cycle into models (notably the faster biological components), but these are not yet routinely incorporated into the models used for making climate projections.

    Please see:

    8.2.3.1 Surface Processes

    The addition of the terrestrial biosphere models that simulate changes in terrestrial carbon sources and sinks into fully coupled climate models is at the cutting edge of climate science. The major advance in this area since the TAR is the inclusion of carbon cycle dynamics including vegetation and soil carbon cycling, although these are not yet incorporated routinely into the AOGCMs used for climate projection (see Chapter 10).

    AR4WG1, Chapt 8 (2007), pg. 604

    *

    Furthermore, there has been only one systematic evaluation of carbon models that were coupled to climate models.

    Please see:

    8.3.4.3 Surface Fluxes

    The only systematic evaluation of carbon models that were interactively coupled to climate models occurred as part of the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP), where Friedlingstein et al. (2006) compared the ability of a suite of models to simulate historical atmospheric CO2 concentration forced by observed emissions. Issues relating to the magnitude of the fertilization effect and the partitioning between land and ocean uptake were identifi ed in individual models, but it is only under increasing CO2 in the future (see Chapter 10) that the differences become large. Several other groups have evaluated the impact of coupling specific models of carbon to climate models but clear results are difficult to obtain because of inevitable biases in both the terrestrial and atmospheric modules (e.g., Delire et al., 2003).

    AR4WG1, Chapt 8 (2007), pg. 618

    The systematic study to which they are refering is:

    Climate–Carbon Cycle Feedback Analysis: Results from the C4MIP Model Intercomparison (abstract)
    P. FRIEDLINGSTEIN,et al
    Journal of Climate, Vol 19, 15 Jul 2006
    http://nora.nerc.ac.uk/327/

    This is the C4MIP Intercomparison study mentioned above. I would certainly recommend it.

    *

    In any case, it would appear that they are testing the waters, but they have not incorporated the carbon cycle as of yet. Such tests are merely experimental, tentative, and are not routinely included in climate projections – any more than ice sheets are. As such, even in the case of the carbon cycle, it would appear that WG1 AR4 deviated very little if at all from fast feedback Charney climate sensitivity.

    Thus when they make projections of 3 C per doubling, this is not taking into account slow feedbacks – which (according to Hansen’s analysis) double the long term climate sensitivity.

    Comment by Timothy Chase — 29 Oct 2007 @ 12:46 AM

  84. Correction to 81, response to Charles Muller regarding climate sensitivity and transient climate response…

    In the paragraph summarizing the inertia of the climate system in the context of fast feedbacks:

    That takes time. So does the warming of the ocean, or for that matter, even the water vapor feedback as the increasing partial pressure water vapor is both a response to higher temperatures and a cause of higher temperatures – but can raise temperatures only against the thermal inertia of the ocean. As such, when emissions quit raising the temperature, it will still take a considerable amount of time for the system to reach equilibrium.

    The last sentence should read:

    As such, when emissions quit rising, according to their framework, the climate system is no longer being forced, but the temperature will continue to rise and it will still take a considerable amount of time for the system to reach equilibrium.

    Comment by Timothy Chase — 29 Oct 2007 @ 1:17 AM

  85. What is “relative probablity”? (The y-axis in the chart.)

    Comment by Anders Lundqvist — 29 Oct 2007 @ 4:19 AM

  86. #78 David wrote :
    “How many times do Spencer and Christy have to be proven wrong before people like you stop uncritically quoting their results?”

    Quite simple: as long as they publish in peer-review scientific literature rather than necromancy magazines. Of course, you’re free to ignore their climatologies, enact there’re a priori wrong and consider tropical warm events of the recent years have produced positive feedbacks TOA. Something like: “Some UAH team data have been corrected in the past, so UAH team data are false by nature and will be corrected in the future”. This kind of inductive assumption is a strange basis for the critical thinking you advocate, no ?

    Comment by Charles Muller — 29 Oct 2007 @ 4:49 AM

  87. Dear RC, Is it not possible that scientists and mathematicians from the science of non linear dynamics (which maths I am presuming is being used in the maths of climate models)to shed light on the amplification and dampening of the climates feedback cycles and hence the so called “sensitivity” issue and hence the possible range of temperatures ?

    Real climate has forever stated that Delta is going to be 3 C with a atmospheric doubling of pre industrial CO2 levels but now lots of people are suggesting that 450 ppmv has a high probability of reaching 2C of warming which because of sinks becomming sources at this temperature level presupposses 3C due to this high level of positive feedback?

    450 ppmv is some 30-40 years away. Is this the current scientific nad political slant on this subject ?

    Comment by pete best — 29 Oct 2007 @ 7:02 AM

  88. [[Please, please show me just one quantitative paper where a doubling of atmospheric CO2 produces a temperature change of X or Y degrees, even if it’s negative. ]]

    Try here:

    http://members.aol.com/bpl1960/ClimateSensitivity.html

    Comment by Barton Paul Levenson — 29 Oct 2007 @ 7:39 AM

  89. [[Some prominent individuals have suggested that the disintegration of the West Antarctic Ice Sheet is part of an overall climate “tipping point.” I have heard that is supposed to be reached by December 6, 2015.]]

    I don’t see how anybody could predict it that exactly.

    Comment by Barton Paul Levenson — 29 Oct 2007 @ 7:41 AM

  90. Patrick Henry @81: ~2000ppm is three doublings from the pre-industrial 280 ppm. So, if accurate, a measured 10C at 2000ppm would be confirmation of a ~3C sensitivity.

    This is trivial arithmetic.

    However, the Jurassic is basically irrelevant to the modern climate because *everything* was different then (for a very abbreviated list: solar intensity, atmospheric composition, locations of continents, oceans, and climatic zones, axial tilt, orbital dynamics, photosynthetic species). So even if we had accurate data on CO2 and temperature from the Jurassic, we could not deduce anything from them about modern CO2 sensitivity.

    Comment by Nick Barnes — 29 Oct 2007 @ 8:14 AM

  91. Patrick Henry @81: and describing the Jurassic as part of “the historical record” must be some new use of the word “historical” of which I was not previously aware.

    Comment by Nick Barnes — 29 Oct 2007 @ 8:18 AM

  92. Charles Muller Says:
    29 October 2007 at 4:49 AM
    #78 David wrote :
    “How many times do Spencer and Christy have to be proven wrong before people like you stop uncritically quoting their results?”

    “Quite simple: as long as they publish in peer-review scientific literature …”

    I read their most recent paper. On RC somebody asked about it a few weeks ago. I don’t think anybody responded to the question.

    Quoting from the paper:

    “This decrease in ice cloud coverage is nominally supportive of Lindzen’s ‘‘infrared
    iris’’ hypothesis. …”

    I think I’ve seen that overstated a tad on the more politically inclined blogs.

    Comment by J.C.H. — 29 Oct 2007 @ 9:24 AM

  93. #83 Timothy

    Thank your your precisions and references. If I summarize, the main issue seems the long term feedbacks due to carbon cycle evolution under warming conditions. According to Friedlingstein 2006, the 11 models of CMPIP-M-4 presently conclude to a positive feedback, with (A2 SRES) +20-200 ppm CO2 and +0,1-1,5°C for 2100. These additional feedbacks are not still accounted by GCM models, at least those used in IPCC 2007 for equilibrium climate sensitivity.

    Well, that is an interesting point for the next few years of research (and so the future IPPC AR5). The wide range of the 11 models (factor 10 for additional CO2 atm. concentration) shows that modelization of the physical and biological processes underlying the carbon cycle is still in its infancy.

    What I still miss is, for climate sensitivity at 2xCO2 (540 ppm) we’re discussing here, how you “jump” from a best estimate of 3°C to 6°C. The A2 SRES used by Friedlingstein 2006 go far over the doubling (856 ppm for CO2, but also 3731 ppb for CH4, and, with all other GHGs + negative forcing integrated, a 8,07 W/m2 forcing very different of the 3,7 W/m2 for the sole 2xCO2 used to estimate CS). In spite of this, the worse estimate from CMPIP-M-4 is “just” +1,5°C (I ignore the mean value of the distribution).

    Comment by Charles Muller — 29 Oct 2007 @ 10:06 AM

  94. #92 Spencer el al 2007 paper doesn’t really support the precise mechanism proposed by Lindzen for Iris effect, but more simply observes a strong TOA negative correction associated with warming events at 20°S-20°N (that is : in the 2000-2005 period of observation, the most significative warming episodes of the surface + low troposphere – 40 days or more – leads to a negative SW+LW cloud forcing at the top of the atmosphere). That’s too short to infer a robust conclusion, anyway, and maybe short-term variations toward high temperature are not representative of the long-term warming induced by GHGs. But that’s an interesting piece, because lapse rate / nebulosity / water vapour feedbacks in the Tropics are still a major uncertainty (source of divergence) in models.

    [Response: Spencer et al has nothing to do with the iris effect despite their claims. Their correlations are based on a dynamic mode of variability (the Madden-Julian Oscillation) which has nothing to do with any SST forced response in the clouds. It's just a bad analogy (rather like using the day-night contrast to estimate climate sensitivity). - gavin]

    Comment by Charles Muller — 29 Oct 2007 @ 10:21 AM

  95. do you think the co2 is changing the external makeup of the environemntl

    Comment by chris — 29 Oct 2007 @ 11:48 AM

  96. #92 J.C.H.: I think I’ve seen that overstated a tad on the more politically inclined blogs.

    What’s that supposed to mean? Just because somebody quotes a statement like that to make a politically motivated point, anything supporting the iris theory (whatever one thinks about it) must be bad science?

    Comment by henning — 29 Oct 2007 @ 12:04 PM

  97. pete best (87) — The current CO2 concentration in the atmosphere is 384 ppm and growing at 2 ppm per year. Assuming this growth continues, the earth reaches 450 ppm in 32 years, 2039 CE.

    Comment by David B. Benson — 29 Oct 2007 @ 12:12 PM

  98. http://environment.newscientist.com/article/mg19626273.300-exxons-funding-of-polar-bear-research-questioned.html

    “… researchers, including Willie Soon of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, published their findings as a “viewpoint”, which is not peer-reviewed. They conclude that the polar bears are not threatened by climate change (Ecological Complexity, DOI: 10.1016/j.ecocom.2007.03.002)….”

    Comment by Hank Roberts — 29 Oct 2007 @ 12:22 PM

  99. I would like to echo Anders question in comment 85. The “relativity probability” shown on the vertical axis in the graph shows values greater than one?! How does this happen? Since the probability of an outcome is always between 0 and 1, how do they derive a probability greater than one?

    Comment by Lawrence Brown — 29 Oct 2007 @ 12:52 PM

  100. I’ll ask it again. What do Roe & Baker include as “f” feedbacks? (I don’t have access to the article.)

    Comment by Lynn Vincentnathan — 29 Oct 2007 @ 1:06 PM

  101. Anders (85) and Lawerence Brown (99) — To me, relative X means the ratios of two Xs. In this case it seems to be the ratio of two probabilites, so any extended real number.

    Comment by David B. Benson — 29 Oct 2007 @ 2:19 PM

  102. (101) Oops! Any non-negative exended real number.

    Comment by David B. Benson — 29 Oct 2007 @ 2:34 PM

  103. Charles Muller (#93) wrote:

    #83 Timothy

    Thank your your precisions and references. If I summarize, the main issue seems the long term feedbacks due to carbon cycle evolution under warming conditions. According to Friedlingstein 2006, the 11 models of CMPIP-M-4 presently conclude to a positive feedback, with (A2 SRES) +20-200 ppm CO2 and +0,1-1,5°C for 2100. These additional feedbacks are not still accounted by GCM models, at least those used in IPCC 2007 for equilibrium climate sensitivity.

    Agreed. And obviously there is a great deal of a difference between 20-200 ppm and what would be required to result in another doubling. However, no one that I am aware of is projecting that all “slow” feedbacks will have reached equilibrium by 2100. Presumably the slow feedbacks could take a millenia or more. Then again they may be a little faster than we expect – and so far the evidence to date would suggest that they are.

    Charles Muller (#93) wrote:

    What I still miss is, for climate sensitivity at 2xCO2 (540 ppm) we’re discussing here, how you “jump” from a best estimate of 3°C to 6°C. The A2 SRES used by Friedlingstein 2006 go far over the doubling (856 ppm for CO2, but also 3731 ppb for CH4, and, with all other GHGs + negative forcing integrated, a 8,07 W/m2 forcing very different of the 3,7 W/m2 for the sole 2xCO2 used to estimate CS). In spite of this, the worse estimate from CMPIP-M-4 is “just” +1,5°C (I ignore the mean value of the distribution).

    If I were basing the claim that 3 C fast feedbacks translates into 6 C once you include slow feedbacks simply on the basis of the carbon cycle and as I pointed out above claiming that the entire system would reach equilibrium, that might be problematic. But I am not claiming that the equilibrium of slow feedbacks will be achieved by 2100, nor am I claiming that only feedbacks from the carbon cycle will be involved.

    There are other feedbacks.

    Offhand, some of the more significant slow feedbacks will come from the ice sheets. This includes both Greenland and the West Antarctic Peninsula. It may even include parts of the EAIS. And of course it includes the glaciers, such as those associated with the Tibetean Plateau. All of these have albedo effects and all are “slow” feedbacks which are considerably more sensitive than we expected – given a variety of feedbacks which we hadn’t even been aware of before.

    Additionally, I do not know precisely what aspects of the carbon cycle have been included. Which models are considering feedback from the biosphere? Ocean? Probably most. How about the permafrost? Have they included the yedoma layer which we didn’t even know about until recently? This is a little more uncertain but may be quite significant.

    Have they included shallow water methane hydrates? I presume some have. Did they include the fact that we are discovering them at much shallower depths than we previously expected them? Perhaps. What about the cracks in the ocean floor which expose deeper deposits to changes in ocean temperature? We hadn’t expected those, either.

    And as you have stated, the coupled modeling which incorporates aspects of the carbon cycle is still in its infancy.

    In any case, I am no expert in this area. Jim Hansen is. But I wouldn’t want you to simply accept his authority in this area, either. There is the paleoclimate record that exists with respect to Antarctica. And presumably it shows that the “slow” feedbacks which are not included in the Charney climate sensitivity roughly doubles the effect of the “fast” feedbacks which are.

    However, both the “slow” and “fast” feedbacks will actually be working at the same time, and the “slow” feedbacks which we are seeing are moving more quickly than has been expected. Likewise, the paleoclimate record that Hansen refers to suggests that the “slow” feedbacks can move surprisingly fast.

    I trust the climate models, but I trust the paleoclimate record more.

    Comment by Timothy Chase — 29 Oct 2007 @ 3:12 PM

  104. Re 101 Thanks David. What I’m curious about is what the numerator and denominator represent. I’ve tried to access the “Summary For Policy Makers” section of the IPCC report without sucess. My version of Acrobat reader(5.0) isn’t bringing the pdf version up . The relative aspect may have something to do with the fact that different versions of different models were used in constructing the graph.

    Comment by Lawrence Brown — 29 Oct 2007 @ 4:00 PM

  105. 96. What’s that supposed to mean? Just because somebody quotes a statement like that to make a politically motivated point, anything supporting the iris theory (whatever one thinks about it) must be bad science?

    Comment by henning — 29 October 2007 @ 12:04 PM

    henning, I intended no colorization of the science in any way. I’m unqualified to do that. The quote is from the scientific paper.

    Does the following reflect nominal support?

    “Lindzen hypothesized cirrus clouds and associated moisture work in opposition to surface temperature changes. The data seemed to indicate that when the Earth’s surface warms, clouds open up to allow heat to escape. A cooling surface, in turn, causes clouds to close and trap heat.

    This elegant, self-regulatory, atmospheric mechanism was soon attacked for being based on limited data and the inability of other researchers to identify the effect in other cloud and temperature data sets.

    New Data Support Theory

    But the new research from the University of Alabama-Huntsville supports the validity of the iris effect. …”

    Comment by J.C.H. — 29 Oct 2007 @ 4:09 PM

  106. Charles Muller (#94) wrote:

    [Re:] #92 Spencer el al 2007 paper doesn’t really support the precise mechanism proposed by Lindzen for Iris effect, …

    Agreed.

    Actually more the opposite (if their analysis were correct) since the clouds under consideration have a higher greenhouse effect associated with them, not a higher albedo effect. Likewise, such cloud coverage is presumably reduced, not increased, entirely counter to what Lindzen expected.

    Charles Muller (#94) wrote:

    … but more simply observes a strong TOA negative correction associated with warming events at 20°S-20°N (that is : in the 2000-2005 period of observation, the most significative warming episodes of the surface + low troposphere – 40 days or more – leads to a negative SW+LW cloud forcing at the top of the atmosphere).

    Additionally this is precisely the same area where we see a clear sky super greenhouse effect, so even if cloud coverage were reduced as a negative feedback to the greenhouse effect, the clear sky greenhouse effect itself will still be considerably stronger over these latitudes, not weaker.

    I quote:

    At sea surface temperatures (SSTs) larger than 300 Kelvin, the clear sky water vapor greenhouse effect was found to increase with SST at a rate of 13 to 15 watts per square meter per Kelvin. Satellite measurements of infrared radiances and SSTs indicate that almost 52 percent of the tropical oceans between 20 N and 20 S are affected during all seasons….

    Satellite studies (8–10) have found that for clear skies and SSTs above 298 K, the spatial variation of Ga with SST, dGa/d(SST), exceeds the rate of increase of sea surface emission, ds(SST)4/d(SST) = 4σ(SST)3. For a tropical SST of 300 K, 4σ(SST)3 ~ 6.1 W m-2 K-1. This effect, termed the “super greenhouse effect” (11), occurs in both hemispheres during all seasons. It is also observed for interannual variations of Ga with SST during the El Nino in the tropical Pacific (12). Observations in the tropical Atlantic ocean (11) show that the clear sky downwelling infrared flux incident on the surface (Fa-) also increases faster than the surface emission with increasing SST. The net result is further warming of the surface, which in turn induces additional heating of the atmosphere column above.

    Direct radiometric observations of the water vapor greenhouse effect over the equatorial Pacific Ocean
    F.P.J. Valero, W.D. Collins, P. Pilewskie, A. Bucholtz, and P.J. Flatau
    Science, 274(5307), 1773-1776, 21 March 1997

    Gavin (inline to 94) wrote:

    Spencer et al has nothing to do with the iris effect despite their claims. Their correlations are based on a dynamic mode of variability (the Madden-Julian Oscillation) which has nothing to do with any SST forced response in the clouds. It’s just a bad analogy (rather like using the day-night contrast to estimate climate sensitivity).

    So let me get this straight.

    Spencer et al (2007) is cited as evidence for the iris effect of Lindzen in order to conclude that the negative feedbacks to the greenhouse effect due to clouds will be substantial.

    However,

    1. The mechanism which they claim to have identified is actually the opposite of what Lindzen described, where he claimed that clouds would increase as the result of the greenhouse effect and their albedo effect would hold down temperatures, but in the tropics the clouds that Spencer et al were dealing with presumably become fewer in number.
    2. The clouds actually have a stronger positive feedback component to them, resulting in an increased greenhouse effect.
    3. The effect according to Spencer et al isn’t necessarily all that significant as they describe it as being “nominal.”
    4. Even if clouds were decreasing there would be the clear sky super greenhouse effect where the rate at which downwelling thermal radiation grows relative to increasing temperatures is actually higher in the tropics than the rate at which surface thermal radiation emissions increase.
    5. Their analysis is flawed in the sense that it is actually based upon a poor analogy in which they are not measuring the actual trend of clouds, but periodic behavior associated with an with a climate oscillation (the Madden-Julian) and has nothing to do with the response of clouds to sea surface temperatures (SST).

    I can see why it so often referenced in the skeptic community…

    Quite illuminating – although I suppose it shouldn’t be all that surprising.

    Thank you both.

    Comment by Timothy Chase — 29 Oct 2007 @ 4:23 PM

  107. re#103

    timothy

    ” and the “slow” feedbacks which we are seeing are moving more quickly than has been expected.”

    can you explain this sentence or have you a good proof of that?

    I’m not sure that, for example, both Antarctica peninsula and Greenland ice sheets are rushing into oceans.

    but maybe can you see an anormal increasing of sea level?

    What else about the “slow feedbacks”?

    My posts are moderated (why?, maybe God knows it) so I hope this one can be read.

    Comment by Pascal — 29 Oct 2007 @ 4:49 PM

  108. Pascal –

    Floating ice changes albedo when it melts, not sea level.
    Dr. Bitz’s thread here on Arctic sea ice melt described models of a fairly pessimistic expectation, last spring. Reality was worse this year.

    Comment by Hank Roberts — 29 Oct 2007 @ 5:22 PM

  109. I spoke too soon. I have been able to bring up the Summary For Policymakers of the IPCC Report, containing SPM 6. with projected surface temperature changes. I haven’t figured out what the probabilities are relative to, though there’s plenty of interesting material included.

    Comment by Lawrence Brown — 29 Oct 2007 @ 5:35 PM

  110. Pascal (#107) wrote:

    timothy [wrote]

    ” and the “slow” feedbacks which we are seeing are moving more quickly than has been expected.”

    can you explain this sentence or have you a good proof of that?

    I’m not sure that, for example, both Antarctica peninsula and Greenland ice sheets are rushing into oceans.

    Charles Muller (CM), Phil Scadden (PS) and I (TC) were discussing the distinction between “fast feebacks” and “slow feedbacks.” Apparently when people refer to climate sensitivity as being ~3 C, this is simply according to the Charney analysis from the 1970s which includes only what are called “slow feedbacks” such as the amplification of the greenhouse effect by water vapor and the albedo effect due to sea ice.

    It excludes feedbacks which “change the boundary conditions” since according to Charney analysis such changes in the boundary conditions would themselves be regarded as “forcings.” The latter set of feedbacks, which include those due to ice sheet instability and the carbon cycle, are normally refered to as “slow feedbacks.” However, given what we are seeing in terms of current climate trends and the paleoclimate record, such a name would seem to be more a matter of wishful thinking than an apt description of the processes involved.

    When Charney analysis speaks of the climate system achieving equilibrium, this only takes into account the “fast feedbacks.” The actual equilibrium, which may occur much later, must include both the “slow” and the “fast” feedbacks. As such, when Charney analysis gives us a climate sensitivity of 3 C this is refering to the unrealistic theoretical construct of the fast feedback equilibrium.

    According to Hansen, the actual long-term climate sensitivity is presumably closer to 6 C. This latter figure comes from the analysis of the paleoclimate record for Antarctica. And it would appear that the projections by the IPCC have been almost entirely limited to those which take into account the “fast” feedbacks, not the “slow” feedbacks.

    Anyway, I believe the full thread for this discussion has been:

    CM #58, TC #70, CM #72, PS #73, TC #74, TC #75, CM #79, TC #83, CM #93, TC #103

    Pascal (#107) wrote:

    I’m not sure that, for example, both Antarctica peninsula and Greenland ice sheets are rushing into oceans.

    Just wait for the positive feedback between the two as the rise in sea level from both starts raising the coastal glaciers off their foundations.

    Pascal (#107) wrote:

    but maybe can you see an anormal increasing of sea level?

    There is more uncertainty there than you might think. Apparently gyres may have been reducing the rise in sea level along the coasts as the climate warms even though the overall sea level was rising — and much of the sea level rise that we attributed to earlier in the twentieth century may actually have happened later in the twentieth century. We may not know for a while though.

    Pascal (#107) wrote:

    My posts are moderated (why?, maybe God knows it) so I hope this one can be read.

    Actually I suspect the blog is having hiccups. Not that big a problem usually, but just this week I had three rather longish posts not go up and I honestly don’t think the moderators had anything to do with it. But in retrospect not that great a loss.

    Comment by Timothy Chase — 29 Oct 2007 @ 5:50 PM

  111. Lawerence Brown (104) — Your final sentence appears to me to explain the notion of relative probablity about as well as what is in the SPM.

    Comment by David B. Benson — 29 Oct 2007 @ 6:02 PM

  112. Pascal (#107) wrote:

    I’m not sure that, for example, both Antarctica peninsula and Greenland ice sheets are rushing into oceans.

    Sorry, I misread this sentence.

    Well, as one example, within the past decade we have seen the Greenland’s melt (as measured in terms of volume) double in the decade 1996-2006.

    Please see:

    Changes in the Velocity Structure of the Greenland Ice Sheet
    Eric Rignot and Pannir Kanagaratnam
    Science 17 February 2006: Vol. 311. no. 5763, pp. 986 – 990
    DOI: 10.1126/science.1121381
    http://www.sciencemag.org/cgi/content/abstract/311/5763/986

    Likewise, icequakes of Greenland tripled over a decade’s time, we have seen ice sheets along Antarctica disintegrate, after the disintegration of the ice sheets we have seen glaciers increase their speed of descent towards the ocean by as much as a factor of 10. Granted, it is “slow” right now, but the melting has been increasing quite substantially, and whereas the IPCC had been speaking in the neighborhood of a sea level increase of 50 cm, figures between one to two meters are becoming common as the result of the observed higher rates since, and with the nonlinear processes and resulting positive feedback, Jim Hansen has suggested that a sea level doubling per decade and increase of several meters (up to 5 m) by the end of the century is more realistic.

    Additionally, we appear to be seeing positive feedback in the carbon cycle from both the South Ocean and the vegetation (for the latter, during the warmer, drier years), positive feedback which we did not expect to see for several decades.

    If you would like more references, I can certainly look these up later this evening, but all of this has been covered before and is well-known. And frankly after the the discussion which you were responding to, I am a little referenced out at the moment.

    Comment by Timothy Chase — 29 Oct 2007 @ 7:12 PM

  113. Pascal (#107) wrote:

    I’m not sure that, for example, both Antarctica peninsula and Greenland ice sheets are rushing into oceans.

    Sorry, I misread this sentence.

    Well, as one example, within the past decade we have seen the Greenland’s melt (as measured in terms of volume) double in the decade 1996-2006.

    Please see:

    Changes in the Velocity Structure of the Greenland Ice Sheet
    Eric Rignot and Pannir Kanagaratnam
    Science 17 February 2006: Vol. 311. no. 5763, pp. 986 – 990
    DOI: 10.1126/science.1121381
    http://www.sciencemag.org/cgi/content/abstract/311/5763/986

    Likewise, icequakes of Greenland tripled over a decade’s time, we have seen ice sheets along Antarctica disintegrate, after the disintegration of the ice sheets we have seen glaciers increase their speed of descent towards the ocean by as much as a factor of 10. Granted, it is “slow” right now, but the melting has been increasing quite substantially, and whereas the IPCC had been speaking in the neighborhood of a sea level increase of 50 cm, figures between one to two meters are becoming common as the result of observed changes, and with the nonlinear processes and resulting positive feedback, Jim Hansen has suggested that a sea level doubling per decade and increase of several meters (up to 5 m) by the end of the century is more realistic.

    Additionally, we appear to be seeing positive feedback in the carbon cycle from both the South Ocean and the vegetation (for the latter, during the warmer, drier years), positive feedback which we did not expect to see for several decades.

    If you would like more references, I can certainly look these up later this evening, but all of this has been covered before and is well-known. And frankly after the the discussion which you were responding to, I am a little referenced out at the moment.

    Comment by Timothy Chase — 29 Oct 2007 @ 7:12 PM

  114. Great to see a paper addressing the uncertainty range. I always wondered about the IPCC 2001 report which showed the predicted global temperatures for 2000-2100 (p34 of the summary for policy makers). I am wondering why the current(2007) global temperatures (rolling average) are below the entire envelope of scenarios given in that graph. Was the uncertainty range underestimated on the low side ? I just have a concern that we reallly ought be be putting forward ranges that are wide enough so that 5-10 years forward from a projection date we are actually inside the range. Otherwise it doesn’t give a lot of credibility to the longer term more alarming view.

    Comment by Imran Can — 29 Oct 2007 @ 7:12 PM

  115. #94 Gavin comment

    “Their correlations are based on a dynamic mode of variability (the Madden-Julian Oscillation) which has nothing to do with any SST forced response in the clouds.”

    Well, you may certainly be right that Madden-Julian Oscillations is the key point, but I’d just like to undertand why. As you do not critic Spencer atl al. 2007 measurements, I suppose there’re right on this point.

    Spencer et al. 2007 choose the peak tropospheric T anomalies in 20°S-20°N (so called “ISOs”). Fig 2A shows that there are (small) positive SST anomalies during these ISOs and (clear) water vapour positive anomalies, at least at the peak of the warming phase of ISOs.

    So, in what way these factors (higher T tropo, higher SST, higher evaporation) differ substantially from a GHGs forced warming (except nominally that they are called “Madden-Julian Oscillations”) ?

    By advance thanks.

    Comment by Charles Muller — 29 Oct 2007 @ 7:47 PM

  116. Anders (85), Lawrence (99, 104), David (101, 108):
    According to the original Figure 10.28 in chapter 10 of AR4 WG1 (p.808), the units are 1/(deg C) – this is characteristic of such plots, which are probability density functions. The total area under each curve is 1; for a given model, the probability of the mean surface temperature change falling between any two temperatures is the area bounded on left and right by those limits, below by the horizontal axis, and above by the curve corresponding to that model. For example – for the curve that looks like a bell curve with a peak of about 0.8 1/C around 3.3 C, you would say that the model gives the probability of the 2090-2099 temperature change falling in the range 3.25-3.35 C as about 0.8 x (3.35-3.25) = 0.08, or 8%.

    Comment by David Warkentin — 29 Oct 2007 @ 8:41 PM

  117. Re 106 – Actually, the ‘iris effect’ mechanism is supposed to involve a shrinking of high cloud area (if it is true), see also http://earthobservatory.nasa.gov/Newsroom/NasaNews/2002/200201167312.html .

    Comment by Patrick 027 — 29 Oct 2007 @ 9:24 PM

  118. Gavin, in your response to comment #41 you stated,”…especially since the winds were even more favorable for ice export in the early 90’s. It wasn’t as warm back then…. – gavin.”
    Now having read the papers you suggested and following them through other papers and links I am uncertain of your meaning in regards to the 90′s as compared to now. It is pretty obvious that the early 90′s positive AO dwarfs the 2006 positve AO and 2004/2005 negative AO, however, the fact that the winds were going in the opposite direction then, seems to indicate to me that they were not favorable to ice export.

    http://www.arctic.noaa.gov/reportcard/ocean.html

    “The sea level time series correlates relatively well with the AO index and with the inverse of the sea level atmospheric pressure (SLP) at the North Pole. Consistent with these influences, sea level dropped significantly after 1990 and reached a minimum in 1996-1997 when the circulation regime changed from cyclonic to anticyclonic.”

    Just to make my position clear, its pretty obvious the arctic is warming, but all that you see here at RC from commentors is that the ice melting is proof of global warming and the disasters that will ensue, when in fact warmth was but a small factor in this years arctic ice minimum.

    As to the specific papers you cited, Miller et al 2006 states,”Recent changes in the magnitude of the annular patterns have been interpreted as the signature of anthropogenic forcing by changes in the concentration of greenhouse gases (GHGs) or else stratospheric ozone [Shindell et al., 1999; Fyfe et al.,1999; Kushner et al., 2001; Kindem and Christiansen,2001; Sexton, 2001; Gillett and Thompson, 2003; Shindell and Schmidt, 2004; Arblaster and Meehl, 2006].” This seems at odds with Shindell et al 1999, which states,”Polar ozone depletion is a candidate for driving observed stratospheric trends2,20,21, which are correlated with the AO index. However, the simulation SG, where ozone changes are absent, exhibits the same increase in the AO index as SO, where polar ozone chemistry is calculated through an interactive photochemical parameterization22. To identify the effect of ozone forcing, EOFs of wintertime SLP (for simulation SO) were recalculated for two separate periods: December and January versus March and April. Although ozone forcing is largest during the latter period, the multi-decadal trend in the AO index, evident in Fig. 2b, is present only in the December to January variability. This result, along with the nearly identical AO trends in models SO and SG, suggests that ozone forcing is not necessary to increase the AO index or to strengthen the stratospheric polar vortex.”

    So perhaps you could clarify, is it the ozone or is it the ghg’s? And how do you represent stratospheric cooling in the models without having ozone changes?

    Thanks again.

    [Response: I don't follow you at all. Positive AO phase is favorable to ice export from the Arctic, presumably we can agree on that. Last winter's +ve phase was therefore a contributory factor to the loss of multi-year ice this year. However, more and more sustained +ve phases occured previously (in the early 90s) and yet the summer minimum did not get anywhere close to this years values. Therefore, while dynamics probably added to the situation, it is not responsible for the bulk of the trend - which is almost certainly thermal in origin. With respect to potential forcings, strat ozone depletion is a strong candidate for the change in the Southern hemisphere (Thompson and Solomon, 2002) where strat ozone depletion has been strongest and the change in the AAO more significant. In the Arctic (which is in a different regime than in the south), GHGs appear to have an effect, but whether it has yet been demonstrated in the real world is ambiguous. - gavin]

    Comment by Ellis — 29 Oct 2007 @ 9:47 PM

  119. RE #107 & “slow” feedbacks moving more quickly…

    It’s the “geological” mindset or perspective. Sort of like a 1000 years in our time is like a blink of God’s or a geologist’s eye.

    Quickly in geological time could mean years, decades, or even centuries. As for slow, well…

    We will have time to get out of the way of sea rise as it happens, even if it happens much more quickly than expected, and even just by walking away from it. It won’t happen as fast as a sea surge or hurricane.

    However, the tipping points are approaching and once they are passed it may take a long time (in our layperson’s scheme of things) for bad things to happen, but we will have very likely ensured that they will happen — if not to us, then to our progeny.

    For instantce, hydrogen sulfide outgassing is a possibility and that would rapidly kill off a whole lot of life.

    My understanding is if we get to a 3C increase, that will more or less guarantee we will eventually (on a geological time scale) reach 6C (due to these other “slow” feedbacks mentioned in this discussion), and the possibility of really, really bad things happening.

    Comment by Lynn Vincentnathan — 29 Oct 2007 @ 10:16 PM

  120. Patrick 027 (#116) wrote:

    Re 106 – Actually, the ‘iris effect’ mechanism is supposed to involve a shrinking of high cloud area (if it is true), see also http://earthobservatory.nasa.gov/Newsroom/NasaNews/2002/200201167312.html .

    Thank you for the correction. I thought I had read somewhere that he was relying upon albedo, but if Spencer’s study were right, it would actually conform to Lindzen’s original (albeit poorly named) hypothesis.

    Comment by Timothy Chase — 29 Oct 2007 @ 10:32 PM

  121. I had written (#103):

    However, both the “slow” and “fast” feedbacks will actually be working at the same time, and the “slow” feedbacks which we are seeing are moving more quickly than has been expected. Likewise, the paleoclimate record that Hansen refers to suggests that the “slow” feedbacks can move surprisingly fast.

    Pascal quoted the following…

    … and the “slow” feedbacks which we are seeing are moving more quickly than has been expected.

    … then Pascal (#107) wrote:

    can you explain this sentence or have you a good proof of that?

    I’m not sure that, for example, both Antarctica peninsula and Greenland ice sheets are rushing into oceans.

    Ok. Let’s set aside the carbon cycle for the moment and just focus on Greenland and Antarctica…

    Greenland

    Previously when refering to the following paper:

    Changes in the Velocity Structure of the Greenland Ice Sheet
    Eric Rignot and Pannir Kanagaratnam
    Science 17 February 2006: Vol. 311. no. 5763, pp. 986 – 990
    DOI: 10.1126/science.1121381
    http://www.sciencemag.org/cgi/content/abstract/311/5763/986

    … I stated:

    Well, as one example, within the past decade we have seen the Greenland’s melt (as measured in terms of volume) double in the decade 1996-2006.

    However, it has actually more than doubled, going from 90 to 220 cubic kilometers per year.

    From the abstract:

    Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66- north between 1996 and 2000, which rapidly expanded to 70- north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate farther north, the contribution of Greenland to sea-level rise will continue to increase.

    Rignot et al (2006)

    In the main text, they describe glaciers which have continued to have roughly constant mass balance loss, then neighboring glaciers which have suddenly sped up, with one going from a mass loss of 5 to 36 cubic kilometers in nine years.

    Please see:

    In central east Greenland, no flow change is detected on Daugaard-Jensen (Fig. 2E) and Vestfjord glaciers (area 9) in 1996 to 2005. The 3.7-km/year frontal speed of Daugaard- Jensen is identical to that measured in 1969 (10), and the glacier is in balance. Immediately south, Kangerdlugssuaq Glacier has been stable in speed since 1962, but was thinning and losing mass in 1996 (11). The glacier must have longitudinally stretched the 1-km thick ice to thin it by 250 m. The acceleration increased the mass loss from 5 km3 ice/year in 1996 (12) to 36 km ice/year in 2005 (Table 1), which is 6% of Greenland’s total accumulation.

    Rignot et al (2006)

    Likewise, according to another paper (Eckstrom et al, 2006) icequakes in Greenland have more than tripled in one decade’s time.

    Recent evidence suggests that ice sheets and their outlet glaciers can respond very quickly to changes in climate, primarily through dynamic mechanisms affecting glacier flow (12, 15). The seasonal signal and temporal increase apparent in our results are consistent with a dynamic response to climate warming driven by an increase in surface melting and the supply of meltwater to the glacier base. The number of events detected at each outlet glacier using the global seismic network is relatively small, and it is therefore difficult to draw robust conclusions about behavior at any single glacier. However, both the seasonal and temporal patterns reported here are observed for independent subsets of the data corresponding to east and west Greenland. The increase in number of glacial earthquakes over time thus appears to be a response to large-scale processes affecting the entire ice sheet. We note also that a part of the increase in the number of glacial earthquakes in west Greenland is due to the occurrence of more than two dozen of these earthquakes in 2000 to 2005 at the northwest Greenland glaciers, where only one event (in 1995) had previously been observed.

    Seasonality and Increasing Frequency of Greenland Glacial Earthquakes
    Goran Ekstrom, Meredith Nettles, Victor C. Tsai
    Science Vol 311, 24 Mar 2006

    Ekstrom et al (2006) provide two charts, one of which shows that the glacial earthquakes (sometimes refered to as “icequakes”) have more than tripled between 1995 and 2005. These are reproduced by Tamino:

    Ice Quakes more than tripled in Greenland between 1995 and 2005.
    http://tamino.wordpress.com/2007/03/30/greenland-tremors/

    Incidentally, the numerical data (including latitude, logitude, direction, time lag, and surface wave magnitude) is given in:

    Analysis of glacial earthquakes
    published 14 April 2007
    Victor C. Tsai and Goran Ekstrom
    Journal of Geophysical Research, Vol. 112,
    F03S22, doi:10.1029/2006JF000596, 2007

    Interestingly, they note that there is a characteristic size to the quakes, so while they should remain of roughly the same magnitude, their number can be expected to increase. Elsewhere it has been noted that melting is increasingly moving northward and towards the center of Greenland.

    Antarctica

    Overall we know that the mass balance of Antarctica is decreasing, with most of this occuring in the West Antarctic Peninsula.

    I quote:

    Abstract: Using measurements of time-variable gravity from the Gravity Recovery and Climate Experiment satellites, we determined mass variations of the Antarctic ice sheet during 2002–2005. We found that the mass of the ice sheet decreased significantly, at a rate of 152 +/- 80 cubic kilometers of ice per year, which is equivalent to 0.4 +/- 0.2 millimeters of global sea-level rise per year. Most of this mass loss came from the West Antarctic Ice Sheet.

    Measurements of Time-Variable Gravity Show Mass Loss in Antarctica
    Isabella Velicogna and John Wahr
    Science 311, 1754 (2006)

    Only a few years before they thought that the mass balance of Antarctica would increase for a while due to increased precipitation in the interior. It might have been at the time but this has changed. They are showing some very slight growth in EAIS as the result of precipitation increase it would appear, but this is quite small in comparison to the melt loss in WAIS. Additionally, while in the past melting has been limited to the West Antarctic Peninsula, it is now moving inland and large areas of melt have been detected as far south as 85 degrees, within about 500 km of the south pole.

    Please see:

    NASA Finds Vast Regions of West Antarctica Melted in Recent Past
    05.15.07
    http://www.nasa.gov/vision/earth/lookingatearth/arctic-20070515.html

    … for a satellite image map of the melt areas. As mentioned in the text, this was quite unprecedented.

    Then of course you have the collapse of several major ice sheets.

    When the ice sheets go, the glaciers which they buttress pick up speed. In a study of eight Antarctic glaciers, they found that speeds of descent increased by as much as a factor of eight after the loss of the Larsen B ice sheet.

    Please see:

    Interferometric synthetic-aperture radar data collected by ERS-1/2 and Radarsat-1 satellites show that Antarctic Peninsula glaciers sped up significantly following the collapse of Larsen B ice shelf in 2002. Hektoria, Green and Evans glaciers accelerated eightfold between 2000 and 2003 and decelerated moderately in 2003. Jorum and Crane glaciers accelerated twofold in early 2003 and threefold by the end of 2003. In contrast, Flask and Leppard glaciers, further south, did not accelerate as they are still buttressed by an ice shelf.

    Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B ice shelf
    E. Rignot, G. Casassa, P. Gogineni, W. Krabill, A. Rivera, and R. Thomas
    Geophysical Research Letters, Vol. 31, L18401, doi:10.1029/2004GL020697, 2004

    They conclude with a warning that the phenomena may spread beyond the reaches of the West Antarctic Peninsula to the main continent itself.

    Please see:

    Further south, glaciers drain larger reservoirs of ice, and the
    thinning of Larsen C [Shepherd et al., 2003] may trigger an even larger contribution to sea level. These observations are also particularly relevant to the evolution of ice streams and glaciers draining West Antarctica. Although the climate conditions of the Antarctic continent are colder and drier than in the Peninsula, ice shelf thinning could be caused by a warmer ocean instead of warmer air temperatures. As ice shelves thin and eventually break up, the large continental glaciers draining West Antarctica could accelerate and precipitate the ice sheet into a state of negative mass balance. This is in fact what we believe is happening in the Amundsen Sea sector of West Antarctica [Rignot et al., 2004].

    ibid.

    Glacier retreat is widespread along the West Antarctic Peninsula – and it is sweeping further south. Here is something from a non-technical article.

    The first comprehensive study of glaciers on Antarctic Peninsula has uncovered widespread glacier retreat and suggests that recent climate change on the peninsula is responsible.

    Eighty-seven percent of the 244 marine glaciers have retreated over the last 50 years, a new study says. The widespread glacier retreat began at the northern, warmer tip of the Antarctic Peninsula. As atmospheric temperatures rose along the peninsula — more than 2.5 degrees Celsius (4.5 degrees Fahrenheit) in the last 50 years — the trend of retreat moved south toward colder mainland Antarctica.

    Glaciers from Antarctic Peninsula in Widespread Retreat, Science Study Says
    April 21, 2005
    http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2005/2005042118836.html

    The technical paper is here:

    Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century
    A. J. Cook, A. J. Fox, D. G. Vaughan, J. G. Ferrigno
    Science 22 April 2005:
    Vol. 308. no. 5721, pp. 541 – 544
    DOI: 10.1126/science.1104235
    http://www.sciencemag.org/cgi/content/abstract/308/5721/541

    What we are seeing is accelerating and it is spreading. “Slow” feedbacks which are proving surprisingly nimble. Of course the paleoclimate record says that things can move a great deal more quickly – but we can save that for later.

    Comment by Timothy Chase — 30 Oct 2007 @ 12:18 AM

  122. #119 (or #118 if 112-113 doubling is corrected)
    Lynn wrote :
    It’s the “geological” mindset or perspective. Sort of like a 1000 years in our time is like a blink of God’s or a geologist’s eye.
    Quickly in geological time could mean years, decades, or even centuries. As for slow, well…

    You underscore a problem: accounting for “slow” feedbacks suppose that a climate model or a carbon cycle model run for centuries. But is there any sense for such an exercise? Let’s consider the biological pump: how can we reasonably constrain adaptative processes on a century or millenia time scale, especially for oceanic fauna and flora with a high reproduction (so mutation) rate? So, Timothy (#103) may be right to look after paeloclimate rather than climate models projections on that point.

    On a more theoretical point of view, we’re discussing here the climate sensitivity as defined by IPCC (equilibrium surface temperatture after a CO2 doubling – 3,7 W/m2 – and all feedbacks integrated). The problem in the “slow” feedback analysis is that it seems a never-ending runaway : there are positive feedbacks (ice melting, carbon pump saturation) ; which imply less albedo, more CO2 ; which imply new positive feedbacks (more ice melting, more carbon pump saturation)… and so on. But of course, that would be an absurd reasoning (a 0,5 W/m2 initial forcing would be enough to engage Venus-like runaway!). I suppose that for a 3,7 W/m2 forcing, the additional energy of forcing+feedbacks is used for faster processes (melting ice, evaporation, warming of subsurface oceanic layers, etc.) and the new equilibrium is reach on a quite short timescale. Any information about that (how long are the GCMs runs when they evaluate 2xCO2 CS?)

    Comment by Charles Muller — 30 Oct 2007 @ 2:24 AM

  123. Timothy

    re (#103)

    thanks for your responses and links.

    Be sure I don’t contest measurements and studies of ice-sheet melting in Greenland and Antarctica.
    I don’t contest also the relatively recent decreasing of CO2 ocean sink.
    I just ask why we don’t see a perceptible acceleration of sea level increasing (you answer on this point) and, for CO2, why we don’t see a greater slope on CO2 concentration curve.

    CO2 emissions are more and more important, the sink is decreasing, and the slope is the same.

    How can we explain this?

    Comment by Pascal — 30 Oct 2007 @ 2:26 AM

  124. Hank Roberts, first my apologies. I often post before thinking.

    This was the December 6, 2015 “tipping point” reference. I’m sure I never “heard this” anywhere and shouldn’t have implied that I did.

    I added 10 years to the AGU date. It was a calculation based on the available data. Perhaps it is in error.
    http://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdf

    Although, other people are sort of using the same timeframe.

    http://www.ens-newswire.com/ens/jun2007/2007-06-01-01.asp

    Oddly enough, I am a great admirer of Dr. Hansen. Much of what he says is undeniably true. But are any of us perfect?

    Comment by petefontana — 30 Oct 2007 @ 2:49 AM

  125. #109 Timothy

    I don’t really understand the “clear sky super greenhouse effect” from Valero et al 1997, or in what way this cancel an Iris or Iris-like effect. Clear sky recent observations suggest a positive feedback, that is an increase of specific humidity in upper troposphere (recent works of Allan, Soden, Wong, etc.) and a consequent diminution of OLR. But Spencer et al 2007 take account of all sky conditions (cloudy and uncloudy – see fig 2-D) when they estimate the SW+LW radiative budget.

    Comment by Charles Muller — 30 Oct 2007 @ 2:50 AM

  126. #107 (Pascal) #112 (Timothy)

    If continental ice melting (Greenland, Antarctic, terrestrial glaciers) is accelerating and if warming of the 0-700 m (and deeper) oceanic layer is still on, you shoud observe a higher rate of sea-level rise. But it is not the case according to Topex-Jason-Poseidon. I think that’s what Pascal has in mind. Lombard et Cazenave 2005 have showed that 20th century sea level thermosteric evolution is still dominated by decadal oscilations, with eventually negative values, even in the second part of the century. But are we in such a negative oscillation (if so, Levitus or Lyman should have observed a cooling) ?

    Comment by Charles Muller — 30 Oct 2007 @ 3:49 AM

  127. Group, thanks for the explanation. Everything understood.

    The GIMBI index seems to be rising quite rapidly.

    Not a bad thing, I would have thought. Soemthing about something concentrating the mind.

    Comment by Eachran — 30 Oct 2007 @ 5:45 AM

  128. Lyn, it’s not just a matter of walking away from the water’s edge. It’s more a matter of having somewhere useful to walk towards. A place that provides enough food and other necessities.

    Cycle thru
    http://cegis.usgs.gov/video/sealevel_world.avi
    a few times to see how far we have to run, and what’s left at 80m of sea level rise.

    All the high quality coastal soils are gone, and the land that’s left may be drought-ridden or utterly unsuitable for agricultural activities.

    We cant afford to rebuild our global infrastructure twice in a millennia, so we have to plan for the worst from the outset. And it will be bad.

    Comment by Nigel Williams — 30 Oct 2007 @ 7:07 AM

  129. > rate of sea level rise

    What? No change? Looks likely it’s real, though hard to quantify yet.
    The satellites are very new and recent data overlapping old data, the whole idea that the planet is a sphere has been tossed as mass concentrations affecting sea level are mapped. It’s ‘arguable’ but that’s the least worrisome thing you can say.

    http://www.realclimate.org/images/sealevel_2.jpg
    http://www.grida.no/climate/vital/19.htm
    http://www.oceansatlas.org/unatlas/projectmanager/atlas_cd/cds_upload/1084987425690_MillerSLRsmall001.jpg

    Comment by Hank Roberts — 30 Oct 2007 @ 9:34 AM

  130. Re 128

    My house is above the 80M high tide mark, but it is not built for the the weather that we are likly to have with global warming. So it will require a retrofit for the new climate.

    However, some part of all of our utilities would be flooded. Power generators. Power substations. Natural gas pumping and control stations. Rail roads (for food). Air ports. Sea Ports. Roads. Drinking water systems. Fuel refineries.

    Just because you are above the high tide mark does not mean you are OK.

    Comment by Aaron Lewis — 30 Oct 2007 @ 11:33 AM

  131. Re #122 & it “may be right to look after paeloclimate rather than climate models projections on that point [of slow feedbacks]…The problem in the “slow” feedback analysis is that it seems a never-ending runaway…But of course, that would be an absurd reasoning (a 0,5 W/m2 initial forcing would be enough to engage Venus-like runaway!).”

    From what RC folks have told me, not so. The Venus-like “PERMANENT RUNAWAY” won’t happen until the sun becomes a big, hot, red ball some billions of years from now.

    However, the paleoclimate info seems to indicate we could go into a “REGULAR RUNAWAY” scenario, that eventually on a geological timescale stops and reverses itself. Some refer to this as “hysteresis” — going out of some bounds, then coming back. For instance the end-Permian mass extinction conditions eventually stopped and the world returned to a life-hospitable state….or we wouldn’t be here to talk about it. My knowledge is limited, but I think such an event could last about 100,000 or 200,000 years. It’s interesting that a portion of our today’s CO2 emissions could be in the atmosphere up to 100,000 years (see: http://www.realclimate.org/index.php/archives/2005/03/how-long-will-global-warming-last ).

    Also, my understanding is we would have to reach about a 3C increase in warming to reach a tipping point on this (at least I hope the tipping point is not at a lower warming level, and hope it is at a much higher level). So I’m not sure where you got the idea that a “0,5 W/m2 initial forcing” would be enough to set us on a hysteresis path, much less a permanent runaway path (maybe that was enough for Venus?).

    I refer to the Venus-like “permanent runaway” as a special case of “runaway” in general, since this term is a metaphor based on runaway horses (or trains), and we know they eventually stop (I got 3 broken ribs and a punctured lung as a kid to prove it). It’s a good layperson’s anthropocentric term, because we are mainly concerned about a situation running away from us (getting out of our control).

    My understanding is that at this point we can control the situation somewhat; reducing our emissions should eventually reduce or stop the warming trend. Once it is out of our control we’re pretty much in for a terrible ride that will amount to much more harm than broken ribs, and no matter how much of our GHG emissions we reduce, there will be virtually nothing we can do about it — except maybe with huge reductions slightly reduce the severity of the harms.

    Skip placing hope in geo-engineering; by that time we will probably be too poor and fighting with each other over rapidly diminishing resources to implement anything, even if some genius were to actually come up with a workable solution without worse-than-the-cure side effects.

    Best bet is to reduce GHGs now ASAP AMAP.

    Comment by Lynn Vincentnathan — 30 Oct 2007 @ 11:43 AM

  132. RE 122: There is no such problem – there will be no Venus runaway. The positive feedback only operates until a resource runs dry. That is, until all the continental ice has melted, and/or all the permafrost in Alaska, Canada and Siberia has melted. The system then seeks new equilibra and the runaway is ended. The composition and sensitivity of these resources is not well known, hence the end results are unknowable for the time being. Except estimates of sea level rise, of course.

    A few thousand boreholes, properly measured, might throw some light on this issue.

    Comment by Pekka J. Kostamo — 30 Oct 2007 @ 12:09 PM

  133. Thanks Nigel (#128), and here is a set of world maps showing what the world would look like with a 100 meter rise: http://resumbrae.com/archive/warming/100meter.html

    Could you or anyone tell me how much warming there would have to be (and how long it would take, given the lag time) to reach, say, a 30M sea rise? 60M sea rise? Off-hand, wild guessimates welcome (think possibilities, not high necessarily probabilities).

    I’ve started writing a fictional story about this and just want some ballpark ideas. While I don’t mind erring a bit on the side of going beyond what conservative estimates scientists might have (it IS a sci-fi story, afterall), I don’t want to extremely overshoot the science, like WATERWORLD or DAY AFTER TOMORROW did.

    With my limited knowledge, I’m just guessing that if we do reach 6C warming by 2100 or 2200 that at least by 2000 years from now the sea would have risen 60M. And if we reach just shy of 3C warming (or whatever the tipping point is) by 2100 or 2200 (but do not trigger limited runaway warming or hysteresis), that by at least 2000 years from now the sea level would have risen about 30M.

    Anyone??

    Comment by Lynn Vincentnathan — 30 Oct 2007 @ 12:26 PM

  134. Timothy Chase @121: please take care to use the terms “ice sheet” and “ice shelf” correctly. Ice shelves float; ice sheets don’t. We haven’t lost any ice sheets. Ice shelves such as Larsen B, on the other hand, have gone (and shrunk).

    Comment by Nick Barnes — 30 Oct 2007 @ 12:34 PM

  135. Pascal Says at 30 October 2007, 2:26 AM
    “I just ask why we don’t see a perceptible acceleration of sea level increasing”

    There is some evidence of just that:
    Abdalati, “Ice Sheets, Glaciers and Rising Seas” (a search for the title should get you to the presentation) has a graph of the Jason/Topex/Poseidon data. also in Lombard et al,Earth and Planetary Science Letters, 254, 2007
    In Fig. 6. You can easily see that the sea level rise has increased from 2 mm/yr in the middle 90s to to 4mm/yr today.For those who want to play with the data: see
    http://podaac.jpl.nasa.gov/DATA_PRODUCT/OST/index.html#jason

    Charles Muller Says at 30 October 2007, 3:49 AM
    “Lombard et Cazenave 2005 have showed that 20th century sea level thermosteric evolution is still dominated by decadal oscilations, with eventually negative values, even in the second part of the century.”

    You may wish to see a newer Lombard reference cited above.

    Another interesting paper is Meier et al., Science, 317, 2007, wherein they point out that glaciers (as opposed to Greenland Ice sheet and Antarctica) have dominated the eustatic contribution in this century. They propose that this dominance will continue for most of this century. I fear they are wrong. They have taken the acceleration in melting of the ice sheets to be a constant, and extrapolated into the future century, Hansen has proposed a much more threatening scenario where the rate of icesheet disintegration increases exponentially, doubling every decade. I note that the rate of acceration of melting of Greenland in the Meier reference does lead to doubling of the melt rate in about a decade (although of course they assume that subsequent doublings will take longer). We shall soon see whether Meier or Hansen are closer to the truth.

    sidd

    Comment by sidd — 30 Oct 2007 @ 1:03 PM

  136. With all these apocalyptic scenarios one should keep in mind that mankind will probably not want to afford burning all the fossil fuel in existence but stop doing so at some point, purely because better, cheaper technology becomes available. We should also believe in the future far enough to assume, that climate science will progress and with it our options to actively do something about it. If 20th century technology could/can ruin the planet and 20th century science could detect it (phase 1), 21st century technology will be able to correct it and 21st century science will be able to make sure its done properly (phase 2). Does that mean we shouldn’t worry? Of course not – after all we are in the 21st and science is already telling us what to do about it. So from where I’m standing, phase 2 has begun – and thats a good thing.

    Comment by henning — 30 Oct 2007 @ 1:03 PM

  137. infinite feedback?

    Charles Muller (#122) wrote:

    On a more theoretical point of view, we’re discussing here the climate sensitivity as defined by IPCC (equilibrium surface temperatture after a CO2 doubling – 3,7 W/m2 – and all feedbacks integrated). The problem in the “slow” feedback analysis is that it seems a never-ending runaway : there are positive feedbacks (ice melting, carbon pump saturation) ; which imply less albedo, more CO2 ; which imply new positive feedbacks (more ice melting, more carbon pump saturation)… and so on. But of course, that would be an absurd reasoning (a 0,5 W/m2 initial forcing would be enough to engage Venus-like runaway!).

    Consider the sum (1/2)^1+(1/2)^2+(1/2)^3+…

    It is an infinite sum in the sense that there is an infinite number of terms. However, it approaches but never exceeds 1. This is the case with the kind of feedbacks that we are talking about here. If you just look at amplification of CO2′s greenhouse effect by water vapor, the rise in temperature due to CO2 will result in a certain amount of additional water vapor.

    The water vapor from this first increase in temperature will have its own greenhouse effect, raising the temperature further but by a smaller amount. This additional rise in temperature will result in still more water vapor which will raise the temperature still more, but by a smaller amount.

    And so it continues. But in the end, all of the water vapor adds somewhat less than 1.8 C to the original 1.2 C for a CO2 doubling in the fast feedbacks. (Amplification due to the albedo effect from sea ice will have its share of the pie, too.)

    *

    What applies in the case of the “fast” feedback from water vapor or sea ice applies in the case of the “slow” feedback from the carbon cycle and ice sheets. Although one may analyse it in terms of an “infinite sum” of incremental feedbacks, each additional increment will be smaller, and the total feedback will be finite.

    Comment by Timothy Chase — 30 Oct 2007 @ 1:34 PM

  138. Re. all the posts about Spencer et al 2007, I hope RC will do an article about it, as it’s widely cited on the blogosphere, and it would be nice to have a thorough RC article about it to link to.

    Comment by Dave Rado — 30 Oct 2007 @ 1:36 PM

  139. Lynn, rent WarterWorld, which was apparently mistakenly shown in some theaters that were supposed to be showing AIT. The announcer says all of the world’s ice has melted. As he’s saying this, a graphic of the globe shows the Arctic ice rapidly melting as seas rapidly rise and cover all the continents. The hero, who looks to me oddly like a person who never saw AIT, drinks his own pee and grows gills.

    Kneel at the altar of adaptation. Who needs mitigation?

    A lot can be learned from Dave Rado’s post above: 52. He corrals most of the world’s ice.

    Nick, once parts of the ice sheet are bergs in the ocean, it floats, right! To get people like me thinking through this, once in the drink, has it essentially raised sea level as much as it ever will?

    It snows on Greenland. It’s an amazingly tall chunk of ice. Frank Lloyd Wright did not design it. No engineering firm put it together so it could grow taller forever. It’s a structure, like the bridge to St. Paul. With the edges thinning, or disappearing altogether, how tall can it get?

    Comment by J.C.H. — 30 Oct 2007 @ 1:38 PM

  140. Nick Barnes (#134) wrote:

    Timothy Chase @121: please take care to use the terms “ice sheet” and “ice shelf” correctly. Ice shelves float; ice sheets don’t. We haven’t lost any ice sheets. Ice shelves such as Larsen B, on the other hand, have gone (and shrunk).

    Thank you, Nick. I am not sure how long it would have taken for me to pick up on the difference, but now that I know the difference I will try to keep it in mind from now on.

    Comment by Timothy Chase — 30 Oct 2007 @ 1:43 PM

  141. Re. henning, #136, see See #59 and #74 ( especially point (c)) of the "Gee-Whiz Geoengineering" thread.

    Comment by Dave Rado — 30 Oct 2007 @ 1:55 PM

  142. #132: “There is no such problem – there will be no Venus runaway. The positive feedback only operates until a resource runs dry.”

    True, but this is what happened on Venus too: the process stopped when all crustal rocks had been cooked of their CO2.

    (And in principle reversible: all it takes is suspending a parasol at Venus’ Lagrange point. It will take a long time for the cooling to propagate down to the surface, and all the CO2 and water to rain out and react with the surface rock…)

    Comment by Martin Vermeer — 30 Oct 2007 @ 2:00 PM

  143. @Dave 137
    You make my point. The problem has been identified – even quantified. And the fact that something like the IPCC exists is an indicator for politicians having acknowledged the problem. Of course things should move faster and more decisive (although at least here in Germany some people already claim things move too fast) but politics always tends to be notoriously slow on the uptake. At least we’ve started doing something and the combined social “forcings” of political pressure and ever rising cost of fossil energy move in the right direction. If we keep this up, there’s no reason to assume we’ll end up with a 70m sealevel rise.

    Comment by henning — 30 Oct 2007 @ 2:18 PM

  144. Lynn Vincentnathan (133) — One way to provide estimates is to look at the sea stand rise from LGM to the so-called Holcence Climatic Optimum. That is, roughly, an S-shaped curve over about 10,000 years, a rise of at least 120 meters and involved about 6C warming. For the purposes of your story, however, it is the maximum rates in melt-water pulse 1A times which might be useful to you. About four meters per century, according to Wikipedia.

    However, with the warming imposed as a forcing, I suppose you might up that to one meter per decade?

    Comment by David B. Benson — 30 Oct 2007 @ 2:19 PM

  145. Hmmmm.
    http://www.space.com/scienceastronomy/solarsystem/venus_oceans_020516.html

    (This is entertainment science, not journal science, I didn’t backtrack to see if this is based on anything published)

    —–excerpt follows———

    “How did Earth manage to hold onto all of its water, while Venus apparently lost all of its water?”

    … studying an unusually warm pool of water in the Pacific Ocean northeast of Australia, as well as the atmosphere above it….

    At sea surface temperatures above 80 Fahrenheit (27 C), evaporation loads the atmosphere with a critical amount of water vapor … a controlling factor seems to keep the same thing from happening on Earth.

    Here, sea surface temperatures never reach more than about 87 Fahrenheit (30.5 C), and so the runaway phenomenon does not occur.

    But the scientists are not sure why it does not occur.

    “What is limiting this effect over the warm pool of the Pacific?” asked Richard Young, another member of the research team.

    —– end excerpt——-

    Comment by Hank Roberts — 30 Oct 2007 @ 2:48 PM

  146. Re. 134:

    Timothy Chase @121: please take care to use the terms “ice sheet” and “ice shelf” correctly. Ice shelves float; ice sheets don’t.

    In case any laymen reading this are confused about why the melting of ice shelves contribute directly to rising sea levels even though ice shelves float, it is because they are anchored to the shore ; so they don’t float freely in the same sense that pack ice and icebergs float. However, because they are partly submerged, their direct contribution to sea level rise is much smaller than the contribution made by the melting of an equivalent volume of (land-based) ice sheets.

    However, as Timothy explained in #121, in addition to the direct sea level rise that occurs when ice shelves melt, there is a much larger secondary effect, in that ice shelves act as a brake, greatly reducing the rate of flow of the glaciers behind them from the land to the sea; and when ice shelves melt, the rate of glacier flow increases quite rapidly.

    Comment by Dave Rado — 30 Oct 2007 @ 2:53 PM

  147. Pascal (#123) wrote:

    re (#103)

    thanks for your responses and links.

    Not a problem — although a little bit of work! ;-)

    Pascal (#123) wrote:

    Be sure I don’t contest measurements and studies of ice-sheet melting in Greenland and Antarctica.
    I don’t contest also the relatively recent decreasing of CO2 ocean sink.
    I just ask why we don’t see a perceptible acceleration of sea level increasing (you answer on this point) and, for CO2, why we don’t see a greater slope on CO2 concentration curve.

    CO2 emissions are more and more important, the sink is decreasing, and the slope is the same.

    How can we explain this?

    Water level? Hank responds to this in #129, so I will focus on carbon dioxide.

    You ask:

    I just ask why we don’t see a perceptible acceleration of sea level increasing (you answer on this point) and, for CO2, why we don’t see a greater slope on CO2 concentration curve.

    Perhaps because we have seen just such an acceleration.

    Here is a non-technical article…

    Unexpected Growth In Atmospheric Carbon Dioxide
    ScienceDaily (Oct. 23, 2007)
    http://www.sciencedaily.com/releases/2007/10/071022171932.htm

    … and a quote from the article it is based on:

    Growth in Atmospheric CO2. Global average atmospheric CO2 rose from 280 ppm at the start of the industrial revolution (~1,750) to 381 ppm in 2006. The present concentration is the highest during the last 650,000 years (5, 6) and probably during the last 20 million years (7). The growth rate of global average atmospheric CO2 for 2000–2006 was 1.93 ppm y^-1 [or 4.1 petagrams of carbon (PgC) y^-1, Table 1]. This rate is the highest since the beginning of continuous monitoring in 1959 and is a significant increase over growth rates in earlier decades: the average growth rates for the 1980s and the 1990s were 1.58 and 1.49 ppm y^-1, respectively (Fig. 1).

    OPEN ACCESS: Carbon sink slowdown contributing to rapid growth in atmospheric CO2
    Josep G. Canadell, Corinne Le Quere, Michael R. Raupach, Christopher B. Field, Erik T. Buitenhuis, Philippe Ciais, Thomas J. Conway, Nathan P. Gillett, R. A. Houghton, and Gregg Marland
    Proceedings of the National Academy of Sciences , October 2007.
    http://www.pnas.org/cgi/content/abstract/0702737104v1

    For those who are interested, the technical article above goes into an analysis of the contributions of rising emissions and declining sinks to the increased rate at which CO2 levels are rising.

    Comment by Timothy Chase — 30 Oct 2007 @ 3:01 PM

  148. Re 135
    Try defrosting your freezer. It starts as a drip. Then it is a good trickle. Then there are small pieces of ice falling off. Then there are large pices of ice falling. There is always this sudden transition from, “Oh,Gee! this is going to take all day” to “Wow, that did not take as long as I expected.

    I fear the same for the ice sheets.

    Comment by Aaron Lewis — 30 Oct 2007 @ 3:18 PM

  149. #Sidd 135 Thank you for the reference.

    You can find publications of LEGOS (including Lombard et al. 2007) at this page:
    http://www.legos.obs-mip.fr/fr/equipes/gohs/publis

    The Fig. 6 (T-P and Jason from 1993 to 2006) shows no particular acceleration for the sea leve rise in the most recent years 2002-2006.

    The review of Sheperd and Wingham 2007 gives a best estimate of 0,35 mm/yr for present contribution of Greenland + Antarctica to sea level rise.
    http://www.sciencemag.org/cgi/content/abstract/315/5818/1529

    A doubling / decade of this rate (0,35mm/yr) would give approx. 3,58 m for 2100 (plus thermosteric). Well, isn’t it a bit… pessimistic ? I read some Hansen papers about “dangerous climate change”, but his comparison (notably) with Eemian didn’t convince me (beyong global mean temperature of the two periods, there was a huge solar forcing on Greenland during the thermal maximum of Eemian).

    #Dave 138 I agree with you, a paper on Spencer et al 2007 woud be welcome here.

    #Timothy 137 I agree, ice melting and carbon saturation are finite feedbacks.

    Comment by Charles Muller — 30 Oct 2007 @ 3:37 PM

  150. Re 139
    Cold ice is very strong. Very cold ice is stronger than some kinds of concrete. Ice makes a great foundation if you can keep it cold.

    Ice above 28 F starts to melt under high pressure. Ice above 28F is quite weak. It can flow and deform under your body weight (200 lb/ inch ^2) in a matter of minutes.

    If the ice has a significant amount of water moving through it, then it is unpredictably fragile. Columns of water in moulins can impose significant forces on ice, and in the event of a collapse, the resulting flow is a slurry of ice and water. Consider what happened when such a collapses occurred on Mt Blanc. http://query.nytimes.com/gst/abstract.html?res=9D04E4D81F39E233A25750C1A9619C94639ED7CF

    Temperature is critical in talking about the mechanical properties of ice.

    http://skua.gps.caltech.edu/hermann/ice.htm

    http://www.tms.org/pubs/journals/JOM/9902/Schulson-9902.html

    Comment by Aaron Lewis — 30 Oct 2007 @ 4:32 PM

  151. Timothy

    I know this study:

    Unexpected Growth In Atmospheric Carbon Dioxide
    ScienceDaily (Oct. 23, 2007)

    I’m speaking about the recent years and not about the difference between last decade and 2000-2006

    In the same study, there is the fact that CO2 emissions of 2006 were the highest never seen.

    look at this link and tell me if you see any acceleration.

    http://www.esrl.noaa.gov/gmd/ccgg/trends/

    for the 4 last years there is even a deceleration of 0.08 ppm/y.y

    for sea level you know this link

    http://sealevel.colorado.edu/current/sl_noib_ns_global.jpg

    for the last years I don’t see and calculate any acceleration.

    on the contrary there is a very slight deceleration.
    you can get the data and make the calculation by yourself.

    But, to avoid any confusion, I recall that my present interest is in the recent years and not in the last decades (more climatologically representative)

    In the same way we can ask ourselves why there is an ocean cooling since 2003.

    Maybe, surely, it is the “variability” but, maybe also, there is another phenomenon in ocean mixing.
    If my calculations are good, ocean is enough cold (3.5°C average) to absorb 1600 years of CO2 doubling RF.
    Of course we’ll not go so far as there.

    Comment by Pascal — 30 Oct 2007 @ 5:17 PM

  152. With regard to the certainty of uncertainty I read an article in the UK newspaper the Independent the other day stating that sinks were becomming sources decades earlier than expected. Is this possibly true?

    Comment by pete best — 30 Oct 2007 @ 5:31 PM

  153. Charles Muller (#149) wrote:

    You can find publications of LEGOS (including Lombard et al. 2007) at this page:
    http://www.legos.obs-mip.fr/fr/equipes/gohs/publis

    The Fig. 6 (T-P and Jason from 1993 to 2006) shows no particular acceleration for the sea leve rise in the most recent years 2002-2006.

    Not a large one, but we aren’t exactly expecting a large one as of yet. But looking at the diagram, despite the seasonal variation would seem to be positive trend in the mass component for sea level.

    I am assuming that you aren’t simply looking at the endpoints in the trendlines but are considering the slope of the relevant trendlines? If not, it is worth keeping in mind the fact that there is a statistical slight-of-hand where one cherry-picks the endpoints, claiming that there is no trend when despite the choice of endpoints statistical analysis shows quite the opposite.

    But to make an accurate determination of the trend we would need the actual numbers – then possibly run them through Excel.

    Yet there clearly isn’t a great deal of change in the mass component to sea level rise. However, I would keep in mind the fact that over a decade’s time, we have seen more than a doubling of the rate of loss of mass balance in Greenland, a tripling in icequakes, the warming of the West Antarctic Peninsula resulting in the acceleration of glaciers, the accelerating loss of global glacier mass balance, etc. If things continued at their current rate there wouldn’t be much of a problem for a very long time. But things are changing.

    Charles Muller (#149) wrote:

    The review of Sheperd and Wingham 2007 gives a best estimate of 0,35 mm/yr for present contribution of Greenland + Antarctica to sea level rise.
    http://www.sciencemag.org/cgi/content/abstract/315/5818/1529

    A doubling / decade of this rate (0,35mm/yr) would give approx. 3,58 m for 2100 (plus thermosteric). Well, isn’t it a bit… pessimistic ?

    Would you rather count on… wishful thinking?

    Charles Muller (#149) wrote:

    I read some Hansen papers about “dangerous climate change”, but his comparison (notably) with Eemian didn’t convince me (beyong global mean temperature of the two periods, there was a huge solar forcing on Greenland during the thermal maximum of Eemian).

    Yes, I believe that the huge solar forcing was the forcing responsible for the high temperatures at the time. (CO2 levels were roughly preindustrial 275 ppm, although I believe the peak was 290 ppm.) So to say that “it was the temperatures and the solar forcing” is in a certain sense double-counting. Today we have the high temperatures contributing to ice melt and we have the huge longwave forcing due to higher levels of carbon dioxide. But I wouldn’t count both as if they are independent of one-another.

    And while the albedo of ice is around 0.4 to sunlight, I believe it is closer to aphalt in the infrared spectrum. So in our time ice is experiencing a similar forcing, but with more longwave flux, less shortwave – although we also have the dubious benefit of anthropogenic black carbon emissions. After having dropped nearly to preindustrial levels, they are climbing again as the result of the economic development of China.

    Comment by Timothy Chase — 30 Oct 2007 @ 5:44 PM

  154. #146: my understanding is that ice shelf breakup does contribute to eustatic sea-level rise, as you say, but only a little, and less so for larger ice shelves (the anchoring is more distant). There is also a small contribution to sea-level because of the different density of fresh and salt water. I think, though can’t cite, that both of these effects are small besides the albedo and braking effects.

    More on ice sheets vs ice shelves. From the point of view of an amateur such as myself, there are essentially three ice sheets in the world.

    1. The Greenland Ice Sheet (GIS): 3 million cubic kilometres, averaging 2km thick, covering the great majority of the interior of Greenland. On low-lying land (around sea-level), mostly surrounded by mountains, draining to the sea by various large glaciers. Subject of some specific concern about global warming because of large temperature rises predicted for the arctic, and because of some arctic-specific feedback effects (e.g. the albedo feedback following loss of arctic sea ice). The IPCC says it’ll take a thousand years to melt. Some scientists are increasingly more concerned and less conservative and raise real concerns about major melting before 2100.

    2. The East Antarctic Ice Sheet (EAIS): 25 million cubic kilometres, on various terrain, mostly separated from the sea and from the WAIS by various mountain ranges. The true deep-freeze. Unlikely to melt much any century soon, unless some huge non-linear feedbacks take hold. May grow a small amount with global warming, due to increased precipitation. Let’s cross our fingers and ignore this one, because if it melts then sea-level rises by 60 metres and that’s beyond bad.

    3. The West Antarctic Ice Sheet (WAIS): about 3 million cubic kilometres, averaging around 3 km thick. This is different from the other two in a couple of ways. Firstly, the bedrock it sits on is mostly below sea-level (very far below sea-level in places). Secondly, as well as being drained by a number of glaciers, it also meets the sea in a pair of enormous ice shelves: the Ross shelf and the Ronne shelf. These are akin to enormous glaciers: hundreds of metres thick, floating on the sea, formed mostly by precipitation, steadily flowing out to sea and breaking up into bergs. There are essentially no ice shelves in the arctic (where bergs come from regular glaciers), and none in the antarctic which compare to these two. You can think of the WAIS as a branch of the southern ocean which is filled with ice, and the R&R shelves as the floating boundaries.

    This marine nature of the WAIS causes some concern, because it means that it might be affected by sea-level rise from: if the GIS lets rip, we really don’t know what might happen to the WAIS. The models we have for ice sheet dynamics are quite new, and we have no way of testing them. Also, the stability of the ice shelves is doubtful and without them the ice sheet would probably flow much more rapidly into the sea, finding a new equilibrium after losing a great deal of mass.

    Apart from these last concerns, the WAIS is much less worrying than the GIS, because the huge thermal inertia and albedo effect of the EAIS, the antarctic continent itself, and the large amount of antarctic sea ice in the southern winter, all act to reduce the degree of warming for the WAIS (whereas the GIS is the victim of various unfortunate circumstances which amplify warming there).

    Ice shelves, especially the really large R&R shelves, are of interest for a couple of reasons. If we lose them rapidly then there would be a small rapid sea-level rise, major rapid local effects to do with huge quantities of meltwater, and an albedo feedback effect. But also the shelves are understood to have a braking effect on the glaciers and ice sheets which feed them. Without the ice shelf, ice will flow into the sea more rapidly. We’ve seen this in glaciers after the loss of the Larsen A and B ice shelves (relatively small shelves on the Antarctic Peninsula), and we’ve seen a similar effect in Greenland, where the floating end of the glacier, and the fjord choked with calved bergs, could apparently perform a similar braking function, now lost for several rapidly-retreating glaciers.

    A bit more terminology: “eustatic” sea-level changes are due to changes in the amount of water (e.g. the Greenland ice sheet melting, or growing due to precipitation). “steric” sea-level changes are due to changes in temperature or salinity (water expands as it gets warmer). Most of the sea-level rise we saw in the 20th century was steric: the world got warmer, the sea-level rose. Almost all of the firmly predictable rise for the 21st century is steric: the “18-59cm” number the denialists love to quote from the IPCC is steric rise. The great unknown, which the recent Hansen paper suggests at several metres, is the 21st century eustatic rise, due primarily to ice sheet melting (also melting of polar and mountain glaciers, and of ice shelves).

    Comment by Nick Barnes — 30 Oct 2007 @ 6:09 PM

  155. re 149. Charles Muller, I would be reluctant to do a linear extrapolation for a system with several known positive feedbacks. I certainly don’t think we’ll melt all of Antarctica or even Greenland, but we know from the paleo record very significant melting and sea level rise are possible once the warming epoch gets under way. I would say this is one area where we have a lot of unknown unknowns.

    Comment by Ray Ladbury — 30 Oct 2007 @ 6:22 PM

  156. Re. henning, #143 (in which you refer to my post #141), I’m not sure why you think that simply avoiding a 70m sea level rise would be something to celebrate. As the IPCC WGII report makes clear, even a 59cm sea level rise would be very serious, especially when combined with the many other expected impacts of climate change such a huge rise in:

    a) the frequency and intensity of extreme weather events;

    b) large scale semi-permanent and permanent droughts in many regions; large scale flooding in others; and in some regions a pattern of severe droughts followed by severe flooding;

    c) large scale destruction of many important ecosystems;

    d) mass extinctions;

    e) a huge increase in the incidence of some human diseases such as cholera; and so on.

    As the UNEP report quoted in Timothy’s post points out, “irreversible damage to the world’s climate will be likely unless greenhouse gas emissions drop to below 50% of their 1990 levels before 2050.” (Actually this is conservative – a 60-80% cut is more likely to be required). And as far as our “moving in the right direction” (as you put it) is concerned, there is no evidence that the steps currently being taken or planned by governments will even stop worldwide emissions from continuing to grow (at best they may reduce the rate of growth slightly) – let alone achieving the required cut.

    It is true as you imply that Germany seems to be pulling its weight in this regard; but unfortunately, in terms of firm action (as opposed to talk), most other countries are not. And even Germany is bigger on targets than they are on providing any evidence that they know how they will achieve them.

    The UNEP report states that there has so far been “a remarkable lack of urgency” in the response [to climate change], which the report characterised as “woefully inadequate”. And so far all the signs are that the rate of worldwide emissions growth is rapidly increasing, at just the time when it needs to be drastically reducing.

    Comment by Dave Rado — 30 Oct 2007 @ 6:22 PM

  157. It’s worth adding: one suspected dynamic of WAIS melting is quite different from GIS melting: massive calving. If either Ross or Ronne ice shelf largely breaks up, they will be replaced by open water and sea ice: the WAIS would be directly exposed to the sea. Remember that the base of the WAIS is on bedrock far below sea-level. In this eventuality, scientists believe that pieces of the ice sheet, possibly very large pieces of it, may simply break off and float away.

    This can’t happen to the GIS or the EAIS, which are not below sea-level.

    Comment by Nick Barnes — 30 Oct 2007 @ 6:29 PM

  158. #136 re us weaning ourselves from fossil fuels once “better, cheaper technology becomes available” …

    The better, cheaper tech is already here, and some has been around for over 2000 years (such as passive solar – which profligate us here in the U.S. haven’t taken up). Windmills have also been around a long time and are now very advanced – some are small & quiet & can be mounted on a roof. Then there’s solar, and electric vehicles, and geothermal tech.

    There are reasons corporations don’t like these as much as oil & coal, which bring in more profits, partly from garnering hefty tax-breaks and subsidiies (& I’m not even counting the military expenses of ensuring our supply and flow — which would make a gallon a gasoline skyrocket in price). For instance, EVs have very low maintenance costs, and car companies make a pretty penny off their maintenance side on I.C.E. cars. What’s good for big corps is not necessarily good for the people living on earth, but they are the ones who have the power and set the agenda. While the people pay for the product and for the harms caused by the product.

    Fossil fuel prices are held artificially low, but we are paying for them in full plus, if not fully at the pump, then on April 15th and in higher health/environment costs, even if we drive EVs and have wind-powered electricity.

    Comment by Lynn Vincentnathan — 30 Oct 2007 @ 8:00 PM

  159. Lynn 133. Thanks. A couple of observations. From what I can gather 80m is all ice melted, and that will happen as an S curve where we are currently at 4mm per year cf 2mm per year rise just a wee while ago. This will move up through some big numbers (possibly approaching half a metre a year at worst) as the ice sheets fall to bits, then the annual rate will slacken again as less ice is left to melt. Finally its all gone at 80m.

    But the sad bit after that is that then there is thermal expansion to follow, which will add a few more metres but will occur over a much longer time as the deep ocean warms. So from today until the ice caps are gone and the thermal expansion is done beaches will never stabilise, and so coastal fisheries, shell fish areas and estuaries are gone for quite a while. The coast will just be horrible freshly eroded hill sides and coastal waters full of sediment for thousands of years. These conditions are quite fatal for fish and shell fish spawning, so bang go the world’s major fisheries.

    The second exercise is to move beyond the small scale models of 80m high tide and Google Earth parts of the world like central Russia in detail, looking at elevations. It’s quite shocking to see how far inland the 80m high tide mark is as you run up the river valleys. It looks like much of the area between the Arctic Ocean and the Caspian Sea – Black Sea area will just be a vast archipelago of messy ridges sticking out of a new ocean, even though these areas appear on the large scale maps as being nicely above high tide. The same no doubt applies elsewhere, like India, China, central USA and Australia. The implications for civilisation are most disturbing, and there is no way back.

    Comment by Nigel Williams — 30 Oct 2007 @ 9:04 PM

  160. #158, Thanks Nigel. Now how long would that take to get to, say, a 60m rise, once we’ve reached 6C warming — IF we do reach that, which could happen soonest by 2100, but more likely in a century later, IF we don’t mitigate drastically. I’m thinking many centuries after than for that much ice to melt and the deep oceans to warm.

    In addition to land loss and harm to sea life, there would also be methane clathrates melting, maybe even hydrogen sulfide outgassing at some point.

    It’s like we all a bunch of naughty children playing with matches on a sea of kerosene, and our parents are nowhere to be found.

    Comment by Lynn Vincentnathan — 30 Oct 2007 @ 10:23 PM

  161. Open question (spurred by the 5.6 temblor some 15 miles from my home this evening)…

    As the West Antarctica and Greenland Ice Sheets decay, melt or however you care to describe it, this also means there will be an eventuallt lessening of weight upon the earth’s crust. And I realize for this to be a significant effect it may take a loonngg time, but…

    …will the release of weight trigger quakes, and will the effect be local, or more global?

    Comment by J.S. McIntyre — 30 Oct 2007 @ 10:50 PM

  162. Lynn 160. Have a look at Hansen on this:
    http://pubs.giss.nasa.gov/docs/2005/2005_Hansen.pdf
    He discusses 1 degree, 2 degree and ice/water/air interaction very helpfully, and discusses the critical time constants you are looking at.

    For me; I look at the WAIS and Greenland – the ice they hold entails 15m of sea level rise. With the recent trends and observations of conditions there I can only feel that they are going to loose at least 10% of their mass over the next few decades. 10% = 1.5m = Disaster.

    Comment by Nigel Williams — 30 Oct 2007 @ 11:19 PM

  163. Charles Muller Says 30 October 2007 at 3:37 PM
    “The Fig. 6 (T-P and Jason from 1993 to 2006) shows no particular acceleration for the sea leve rise in the most recent years 2002-2006.”

    please see e.g. :
    http://www.laseagrant.org/forum/docs/03-20-07/WaleedAbdalati.pdf

    on page 10 you will see a graph that may illustrate my point that sea level rise has accelerated.

    if you would look at the data
    http://podaac.jpl.nasa.gov/DATA_PRODUCT/OST/index.html#jason
    and perhaps try your own curve fits, you will see that the rate from 1993 to 1996 was 2 mm/yr and you may see from the Lombard (2007) reference that the 2003-2006 rise is 4mm/yr.

    “A doubling / decade of this rate (0,35mm/yr) would give approx. 3,58 m for 2100 (plus thermosteric). Well, isn’t it a bit… pessimistic ?”

    Quite.

    But i will say this. When i see articles like Velicogna and Wahr, Nature, 443, 2006, informing me that, in the Greenland Ice Sheet (GIS)
    “The rate of ice loss increased by 250 per cent between the periods April 2002 to April 2004 and May 2004 to April 2006″
    it does darken my views. if the doubling time for mass loss in GIS is on the order of years, rather than millenia, what credence may i place on estimates for WAIS and EAIS ?

    i submit that the downside is too big, this wager is too rich for my blood.

    and what of the generations to follow ?

    sidd

    Comment by sidd — 30 Oct 2007 @ 11:32 PM

  164. pete best (#151) wrote:

    With regard to the certainty of uncertainty I read an article in the UK newspaper the Independent the other day stating that sinks were becomming sources decades earlier than expected. Is this possibly true?

    I am not sure that I have heard that story as of yet. However, in a certain sense pretty much all carbon sinks are also carbon sources. The ocean releases carbon dioxide in warm weather, absorbs in the cold. Plants take up carbon dioxide as they grow and release it upon death. But a net carbon sink may become a net carbon emitter – or it may be weakened so that it is no longer acting all that effectively as a carbon sink.

    And the major carbon sinks appear to be weakening….

    With the South Ocean we are seeing a significant decline in its ability to absorb our emissions. However, the mechanism behind this is a little different from what had been expected. Instead of it simply becoming more saturated it, changing atmospheric circulation is resulting in surface winds that cause upwelling of rich organic material from below which then releases both carbon dioxide and methane.

    Please see:

    The CO2 flux variability from the longest inversion correlates with the Southern Annular Mode (SAM), an index of the dominant mode of atmospheric variability in the Southern Ocean. Here we use the SAM definition of Marshall (2003; 19) based on the difference in mean sea level pressure between 40ºS and 65ºS, which is entirely based on observations and fully independent of our inversion. The correlation of the monthly mean anomalies is small (r=+0.22) but significant at the 99% level (16,18). The positive correlation indicates that the ocean outgasses CO2 compared to its mean state when the SAM is positive, i.e. when the winds are intensified South of 45ºS (20), and suggests that wind-driven upwelling and associated ventilation of the sub-surface waters rich in carbon dominates the variability in CO2 flux (18).

    Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change
    Corinne Le Quéré, et al
    Science, Vol 316 22 June 2007

    Open Access from Global Carbon Project page:
    http://www.globalcarbonproject.org/products/SO_ScienceMay07.htm

    The following mechanism is what had actually been expected – and it is occuring rapidly in the North Sea…

    New observations from the North Sea, a NW European shelf sea, show that between 2001 and 2005 the CO2 partial pressure (pCO2) in surface waters rose by 22 matm, thus faster than atmospheric pCO2, which in the same period rose approximately 11 matm. The surprisingly rapid decline in air-sea partial pressure difference (ΔpCO2) is primarily a response to an elevated water column inventory of dissolved inorganic carbon (DIC), which, in turn, reflects mostly anthropogenic CO2 input rather than natural interannual variability. The resulting decline in the buffering capacity of the inorganic carbonate system (increasing Revelle factor) sets up a theoretically predicted feedback loop whereby the invasion of anthropogenic CO2 reduces the ocean’s ability to uptake additional CO2. Model simulations for the North Atlantic Ocean and thermodynamic principles reveal that this feedback should be stronger, at present, in colder midlatitude and subpolar waters because of the lower present-day buffer capacity and elevated DIC levels driven either by northward advected surface water and/or excess local air-sea CO2 uptake. This buffer capacity feedback mechanism helps to explain at least part of the observed trend of decreasing air-sea ΔpCO2 over time as reported in several other recent North Atlantic studies.

    Rapid decline of the CO2 buffering capacity in the North Sea and implications for the North Atlantic Ocean
    Helmuth Thomas, et al
    Global Biogeochemical Cycles, Vol 21, GB4001, doi:10.1029/2006GB002825, 2007

    In the main text the authors note that similar observations have been made in the North Pacific Ocean (2006) and parts of the North Atlantic Ocean (2007).

    There is also a fair amount of evidence that plants are weakening as a carbon sink. However, if so, this would appear to be a function of stress due to heat and drought.

    Please see:

    In general, we find that the remarkable feature of the 2002-2003 anomaly seems to be that climate fluctuations, not only related to El Nino and occurring across all latitudes, acted together to create an unusually strong outgasing of CO2 of the terrestrial biosphere. Further research will be required to investigate if this fluctuation carries features of projected future climate change and the CO2 growth rate anomaly has been a first indicator of a developing positive feedback between climate warming and the global carbon cycle.

    Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002-2003
    Knorr, et al
    Geophysical Research Letters, Vol. 34 (5 May 2007), L09703.
    http://www.agu.org/pubs/crossref/2007/2006GL029019.shtml
    (subscription or purchase)

    Each instance of a carbon sink weakening is an instance of positive feedback from the carbon cycle. With respect to the South Ocean and plants, I believe we weren’t expecting them to weaken significantly for several decades. In time, as the temperature rises, even the oceans may become net emitters as the warmer upper layers lose their capacity to hold the carbon dioxide which they have already absorbed.

    Comment by Timothy Chase — 31 Oct 2007 @ 12:17 AM

  165. Regarding the estimated linear feedbacks used in the paper:

    “Researchers (17, 18) estimated mean and SD of feedback factors calculated from two different suites of climate models. First, Colman (17) found a mean and SD of (0.11, 0.06) for the albedo feedback factor; (0.17, 0.11) for the cloud feedback factor; and (0.42, 0.06) for the water vapor and lapse rate feedbacks combined.”

    “Second, Soden and Held (18) found a mean and SD of (0.09, 0.02) for the albedo feedback factor; (0.22, 0.12) for the cloud feedback factor; and (0.31, 0.04) for the water vapor and lapse rate feedbacks combined. The water vapor and lapse rate feedbacks are typically combined because models show a strong negative correlation between the two. Although the combined feedback for water vapor and lapse rate has the largest magnitude, the greatest contributor to uncertainty is the cloud feedback.”

    17. R. Colman, Clim. Dyn. 20, 865 (2003).
    18. B. J. Soden, I. M. Held, J. Clim. 19, 3354 (2006).

    And the nonlinear feedbacks:

    “The first nonlinearity we consider is that at higher temperatures the T4 dependence of the Stefan-Boltzmann equation means the climate system is able to more effectively compensate for radiation perturbations than at lower temperatures. The second nonlinearity is that the water vapor feedback depends on the moisture content of the air, which via the Clausius- Clapeyron relation is a nonlinear function of temperature. Physically, the Stefan-Boltzmann feedback becomes more negative and the water vapor feedback becomes less positive as the temperature increases.”

    By focusing soley on the equilibrium climate sensitivity, the authors do miss a lot of features important to people about the overall climate system – for example, what’s the equilibrium sensitivity of the carbon cycle to the temperature change brought about by 2X CO2? What are the chances of exhausting carbon sinks? (That would mean that a 50% reduction in CO2 emissions would have no effect on the rate of growth of atmospheric CO2). What are the chances that existing net carbon sinks could turn into net sources of CO2 to the atmosphere (for example, wildfires turn biomass into atmospheric CO2)? At what temperature do such effects kick in?

    Taking a “wait-and-see” approach to such questions seems like a bad idea.

    Comment by Ike Solem — 31 Oct 2007 @ 12:40 AM

  166. J.S. McIntyre (#161) wrote:

    Open question (spurred by the 5.6 temblor some 15 miles from my home this evening)…

    As the West Antarctica and Greenland Ice Sheets decay, melt or however you care to describe it, this also means there will be an eventuallt lessening of weight upon the earth’s crust. And I realize for this to be a significant effect it may take a loonngg time, but…

    …will the release of weight trigger quakes, and will the effect be local, or more global?

    Yes, we can probably expect more conventional earthquakes (as opposed to glacial “earthquakes”), but it should be on what are essentially “short” geological timescales. And it should be local.

    Please see the inline to Climate Insensitivity, comment 92

    Response: I am happy to be able to correct you that tectonic rebound from the Greenland ice sheet won’t have impacts on earthquakes around the world. Big earthquakes are due to processes much deeper in the earth’s crust, and much more localized. It is, on the other hand, rather likely that rising sea levels will help to destabilize the Antarctic ice sheet. On what timescale, however, remains quite uncertain. –eric

    PS

    We aren’t noticing the effect as of yet, either. Greenland’s conventional earthquakes aren’t showing any trend despite the loss of glacial mass balance. So this is one thing we probably won’t have to worry about all that much any time soon.

    [Hmmm. I have been the bearer of good news -- and the world hasn't come to an end. But there could be some sort of lagtime.... I will give it another twenty-four hours just to make sure.]

    Comment by Timothy Chase — 31 Oct 2007 @ 12:53 AM

  167. @Dave Rado 156
    I never said it was reason to celebrate. My point is that we actually have started doing something – and evidence suggests that we’ll do more in the future. You can’t shut down global economy from one day to the next. It takes some time to adjust, to invent new technologies and bring them to market. I’ve read the IPCC reports (well most of them) cover to cover and the current debate in here about signs everywhere indicating that AR4 means nothing and everything will be much worse and much sooner and totally irreversible does not convince me. If that was true, we should demand our money back from the IPCC and rather spend it on a couple of additional life-boats.
    The Problem with Roe and Baker is, that it opens the gates for utter exaggeration. Soon Climate Scientists will have to defend their findings not only against the “it doesn’t exist” folks but even more so against the “in reality it is much worse and you just didn’t calculate your feedbacks scary enough” crowd. We should come back to the modeled basis and not start always quoting the top end of the error bar plus a generous Roe/Baker factor – that won’t help speeding things up – rather produce the notion of too-late-anyway.

    Comment by henning — 31 Oct 2007 @ 3:14 AM

  168. #163

    sidd

    there is a contradiction between the fact that is pointed in this link:

    http://earthobservatory.nasa.gov/Study/Greenland/greenland5.html

    “The second and potentially greater source of the discrepancy is time. Different studies used data from different years. Scientists now know there was a substantial jump in ice loss from 2002 through 2004 compared to previous years. ”

    and the fact that we don’t see any acceleration of sea level increasing in the last ten years.

    look at this graph (built with Univ of Colorado data)

    http://www.host-img.com/visitors/1193819840.jpg

    where can we see a jump since 2002?

    Comment by Pascal — 31 Oct 2007 @ 3:44 AM

  169. OK, I have read all and very interesting it is too.

    I especially dont like the long tail and its implications.

    Some of you seem to be going down the GIMBI (Group (RC) Ice Mass Balance Index) route.

    So to get you started, I say this : 1m sea level rise before 2050.

    You could use 1m by 2050 as the benchmark and calculate the GIMBI from there : thus by trending (you dont have to use straight line) sea level rise to that date and valuing every additional piece of new information as it happens the trend will be affected and therefore GIMBI. So if a chunk of the Greenland ice sheet unexpectedly falls into the water and increases sea level then GIMBI will tend to be in excess of 1. An alternative way of looking at the index is by observing how much closer or further away is the 1m benchmark.

    A simpler way of doing a GIMBI is to ask a team of experts their best guess, and to take an average.

    Dont be shy, when I was working in industry we (all experts) used to have best guesses at exchange rates and interest rates and the like for a Christmas sweepstake the next year : we were always wrong and sometimes disastrously so.

    But all you experts, we laypeople need to know what it is that you really believe. None of this, if and but and maybe stuff : that is for the peer reviewed journals.

    It is a bit of fun too, amidst all the gloom.

    Comment by Eachran — 31 Oct 2007 @ 6:43 AM

  170. NIck Barnes, are you sure that the Greenland Ice Sheet is resting on rock that is at or above sea level? How much above sea level?

    Comment by catman306 — 31 Oct 2007 @ 8:02 AM

  171. catman306 @170: I stand corrected, thank you. The bedrock under the central GIS is depressed by the weight of the ice, and forms a shallow basin reaching 300m below sea-level (cf 2500m under the WAIS). Without the ice, the basin would probably rebound, but we don’t know how far. The basin is surrounded by higher ground. I was right to state that the WAIS is different from the GIS and EAIS: the WAIS meets the sea in the R&R ice shelves, the GIS only feeds the sea through glaciers.

    Comment by Nick Barnes — 31 Oct 2007 @ 8:12 AM

  172. #159,#160
    I think you guys have been watching a little too much Waterworld …. why don’t you compare the IPCC 2001 global temperature rise predictions to current global means (year averages or rolling averages – whatever you want). I think you’ll find the 2007 world is way below the ENTIRE ENVELOPE of the scenarios – which doesn’t say much about the IPCC’s ability to understand the uncertainty on the lowside (topical). And I think you’ll sleep better at night.

    Imran
    PS You can find the graph on p34 of the Summary for Policy Makers.

    Comment by Imran Can — 31 Oct 2007 @ 8:31 AM

  173. Eachran (#169) wrote:

    Some of you seem to be going down the GIMBI (Group (RC) Ice Mass Balance Index) route.

    So to get you started, I say this : 1m sea level rise before 2050….

    A simpler way of doing a GIMBI is to ask a team of experts their best guess, and to take an average.

    Currently the IPCC is consistently underestimating the level of sea level rise. Even prior to any large feedback involving the ice sheets or carbon cycle, the actual rise in sea-level continues to be at the top edge of the envelope of the IPCC’s predictions.

    Please see:

    Rates of sea-level rise calculated with climate and ice sheet models are generally lower than observed rates. Since 1990, observed sea level has followed the uppermost uncertainty limit of the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR), which was constructed by assuming the highest emission scenario combined with the highest climate sensitivity and adding an ad hoc amount of sea-level rise for “ice sheet uncertainty” (1).

    A Semi-Empirical Approach to Projecting Future Sea-Level Rise
    Stefan Rahmstorf
    Science 19 January 2007:
    Vol. 315. no. 5810, pp. 368 – 370
    DOI: 10.1126/science.1135456
    http://www.sciencemag.org/cgi/content/abstract/1135456

    We can do better.

    Please see:

    We can explore the consequences of this semiempirical relationship for future sea levels (Fig. 4), using the range of 21st century temperature scenarios of the IPCC (1) as input into Eq. 2. These scenarios, which span a range of temperature increase from 1.4° to 5.8°C between 1990 and 2100, lead to a best estimate of sea-level rise of 55 to 125 cm over this period. By including the statistical error of the fit shown in Fig. 2 (one SD), the range is extended from 50 to 140 cm. These numbers are significantly higher than the modelbased estimates of the IPCC for the same set of temperature scenarios, which gave a range from 21 to 70 cm (or from9 to 88 cm, if the ad hoc term for ice sheet uncertainty is included). These semiempirical scenarios smoothly join with the observed trend in 1990 and are in good agreement with it during the period of overlap.

    ibid.

    This approximation (very) closely tracks sea-level rise from 1880 to 2000 by assuming that the rate at which height increases is a strict linear function of the temperature with a straight averaging of the calculated rate for a period from 15 years before to the point in time for which height is being calculated (i.e., the embedding period).

    Now this won’t take into account strong positive feedback from the ice sheets or the carbon cycle. Neither will be linear and both have a great deal of uncertainty attatched. This will lead to an underestimation – in the long term. But it also doesn’t take into account the fact that we will be running out of glaciers – which appear to be responsible for more melt than that due to glaciers. This will lead to overestimation. And to some extent the two uncertainties can be expected to compensate for one another, at least in the short term.

    Incidentally, no need to look at the center of the range — as the uncertainty given is largely a function of our bad behavior.

    PS

    I gave Hank and Stefan a hard time when Hank brought this up before. Not sure that they know, but that was me being tongue-in-cheek. I like it. Big improvement.

    Comment by Timothy Chase — 31 Oct 2007 @ 8:47 AM

  174. Well, Imran (#172), that’s just what I wanted to avoid, WATERWORLD science. Where did they get all that water? Not from this planet! (I love sci-fi, but not when it extremely violates the laws of physics or common sense.)

    What MIGHT (possibility, not nec high probability) it look like in 1000 years if much of earth’s cryosphere melts & waters expand if we reach 6C warming is the question. Presumably there is a maximum amount of sea rise, unless those pesky Gorkians from Planet Gork insist on dumping more water on earth to gorkiform it for their inhabitation.

    Comment by Lynn Vincentnathan — 31 Oct 2007 @ 9:04 AM

  175. Correction to #173

    In the second to last paragraph:

    Now this won’t take into account strong positive feedback from the ice sheets or the carbon cycle. Neither will be linear and both have a great deal of uncertainty attatched. This will lead to an underestimation – in the long term. But it also doesn’t take into account the fact that we will be running out of glaciers – which appear to be responsible for more melt than that due to ice sheets. This will lead to overestimation. And to some extent the two uncertainties can be expected to compensate for one another, at least in the short term.

    The italicized sentence should be “But it also doesn’t take into account the fact that we will be running out of glaciers – which currently appear to be responsible for more melt than that due to ice sheets.”

    Comment by Timothy Chase — 31 Oct 2007 @ 9:07 AM

  176. I’m going to work through a thought-experiment… let me know where i screw up:

    First, let’s assume that the vast majority of the WAIS is below sea level and that the percentage above sea level is negligible (anyone know the accuracy of that assumption?). let’s assume that the entire WAIS calves (which, i assume to mean that it breaks away from the continent and floats off into the ocean). That, according to #154, adds 3 million sq km. of ice to the ocean. Almost instantaneously, the sea level will fall (the shelf was displacing its volume, now it’s floating and is displacing it’s weight).

    If that’s correct, then melting the WAIS will lower the sea level, not raise it. the mitigating factor is the aforementioned assumption: how much of the WAIS is currently below sea level?

    Hence we may only need to address the GIS and EAIS as potentially raising the sea level. the EAIS is basically unchanged (some studies say it’s growing, some say its shrinking). The GIS is shrinking. the net result over the last decade or so is basically no change to the sea level.

    which leads me to wonder if all the fears being generated from a 60m sea level rise is simply an emotional argument aimed at trying to scare us…

    and when people resort to emotional arguments on a scientific subject in order to get me to do something, i immediately grab my wallet, because it’s going to cost me.

    Comment by dean_1230 — 31 Oct 2007 @ 9:17 AM

  177. Nick Barnes, because the GIS is a bowl, with it’s bottom below sea level, melt water and heat flow to the bottom, not into the oceans. That heat will probably destabilize the ice mass faster than predicted. The glaciers would flow fast like a river. There are grooves cut into the sea bottom where ice has done this in the past, probably without much warning.

    Comment by catman306 — 31 Oct 2007 @ 9:27 AM

  178. sidd (#163) wrote:

    if you would look at the data
    http://podaac.jpl.nasa.gov/DATA_PRODUCT/OST/index.html#jason
    and perhaps try your own curve fits, you will see that the rate from 1993 to 1996 was 2 mm/yr and you may see from the Lombard (2007) reference that the 2003-2006 rise is 4mm/yr.

    Pascal (#168) responded:

    #163 sidd
    there is a contradiction between the fact that is pointed in this link:

    http://earthobservatory.nasa.gov/Study/Greenland/greenland5.html

    “The second and potentially greater source of the discrepancy is time. Different studies used data from different years. Scientists now know there was a substantial jump in ice loss from 2002 through 2004 compared to previous years.”

    and the fact that we don’t see any acceleration of sea level increasing in the last ten years….

    Two problems.

    The statement by NASA is regarding Greenland. The chart is a chart of the rate of sea level rise. The majority of sea level rise is still due to thermal expansion. Likewise you are omitting the embedding period from your analysis. (See #173)

    Oh, and sidd was comparing 1993-6 to 2003-6. 2 mm/y vs 4 mm/y. The rate has accelerated.

    Comment by Timothy Chase — 31 Oct 2007 @ 9:38 AM

  179. re 157, 170, 171

    NIck Barnes, are you sure that the Greenland Ice Sheet is resting on rock that is at or above sea level?

    =================

    Being one of those members of the peanut gallery wanting specifics, I looked the GIS up just to get an idea of how thick it was. From Wiki:

    “The Greenland Ice Sheet is a vast body of ice covering roughly 80% of the surface of Greenland. It is the second largest ice body in the world, after the Antarctic Ice Sheet. The ice sheet is almost 2,400 kilometres long in a north-south direction, and its greatest width is 1,100 kilometres at a latitude of 77° N, near its northern margin.

    “The mean altitude of the ice is 2,135 metres. [1] The ice sheet covers 1.71 million km², or roughly 80% of the surface of Greenland. The thickness is generally more than 2 km (see picture) and over 3 km at its thickest point. It is not the only ice mass of Greenland – isolated glaciers and small ice caps cover between 76,000 and 100,000 square kilometres around the periphery.”

    That’s quite a bit of ice. Makes me think of Lex Luthor’s obsession with beachfront property….

    http://en.wikipedia.org/wiki/Greenland_ice_sheet

    Comment by J.S. McIntyre — 31 Oct 2007 @ 10:11 AM

  180. There is a graphic on this website that does a good job of showing that GreenLand is changing quickly in more than one way:

    http://earthobservatory.nasa.gov/Library/ICESat/

    Change in Ice Sheet Thickness

    Comment by J.C.H. — 31 Oct 2007 @ 10:11 AM

  181. catman306 @ 174: an interesting conjecture. As I said, we don’t have a good understanding of the ice sheet dynamics, and what you say is plausible at first sight. A few minor points:

    - the central surface of the GIS is colder than the periphery, and the basement of any ice-sheet is well-insulated from the surface. Would melt water reach the central basement of the GIS still carrying much heat? We’d need to model it.

    - I don’t have a topo map of the Greenland bedrock. Anyone?

    - I don’t have a map of the glaciers around the GIS and the ice streams within it. Anyone? If there is a pronounced basin within the GIS, ice streams will not flow to the sea. Presumably this means the GIS will melt in-place??

    - Possibly interesting paper here. Any AGU subscribers who can peruse it and report back? http://www.agu.org/pubs/crossref/2001/2001JD900087.shtml

    - At least some melt water flows along rivers inside (not underneath) the sheet (ref: moulin studies in Greenland in the last couple of years). This is a bit like cave formation in limestone rocks.

    - the WAIS has some interesting ‘fold’ features which suggest rapid flow in the past (ref: Google WAIS fold).

    Comment by Nick Barnes — 31 Oct 2007 @ 10:17 AM

  182. I must say that this particular thread is particularly depressing. Just to note a few points that are touched on by the most recent comments:

    1. Empirically observed effects of anthropogenic warming, eg. melting and sea level rise, are consistently more rapid and more extreme than predicted by models.

    2. Positive feedbacks that either reduce the ability of the Earth system to absorb excess CO2 (saturation or weakening of carbon sinks), or cause the Earth system to emit more CO2 and methane (eg. thawing permafrost), are being observed much sooner than expected.

    3. There are growing indications that the Earth’s biosphere is already suffering from the effects of warming, eg. oceanic phytoplankton, a very high rate of species extinction, and severe damage to entire bioregional ecosystems (eg. the Amazon) that may ported their collapse.

    4. Anthropogenic emissions of CO2 are increasing, and accelerating, and current proposals for reducing them present no plausible scenario in which emissions will actually peak and decline in anywhere near the time frame that is required to avoid what are generally considered “dangerous” levels of CO2 (although points 1-3 above suggest that the current levels are more dangerous than has been generally believed).

    It is very hard to imagine a realistic happy ending to this story.

    Comment by SecularAnimist — 31 Oct 2007 @ 10:20 AM

  183. Nick Barnes- Thanks for finding my conjecture interesting. Every educated person knows that the world wasn’t always as it was on the day they were born. The ice will melt. People who frequent this site might just find out the reason, the when, and how fast.

    Comment by catman306 — 31 Oct 2007 @ 11:36 AM

  184. Tim Chase — there’s a noun wrong in this bit:

    > we will be running out of glaciers – which appear
    > to be responsible for more melt than that due to glaciers.

    Re this

    > PS I gave Hank and Stefan a hard time … being tongue-in-cheek.

    It’s hard to tell at best what the writer was feeling, there’s no emotional tone in ASCII except the reader’s projection, and as you said in a slightly different context “

    Comment by Hank Roberts — 31 Oct 2007 @ 11:53 AM

  185. SecularAnimist – Without disagreeing with your four points, it’s possible that the next dominant species will see evidence of our passing and ponder the reasons. They’ll see the mistakes homo sapiens made, and vow not to repeat them. THAT will be the happy ending.

    Comment by catman306 — 31 Oct 2007 @ 11:58 AM

  186. dean_1230 Says at 31 October 2007, 9:17 AM:
    “First, let’s assume that the vast majority of the WAIS is below sea level and that the percentage above sea level is negligible (anyone know the accuracy of that assumption?)…Almost instantaneously, the sea level will fall (the shelf was displacing its volume, now it’s floating and is displacing it’s weight)”

    this is inaccurate. WAIS would, if melted, contribute as much as greenland to sea level rise.

    Nick Barnes Says, at 31 October 2007,10:17 AM:
    “I don’t have a topo map of the Greenland bedrock. Anyone?”

    here is one i made a while ago from nsidc data:
    http://membrane.com/sidd/greenland.html

    “I don’t have a map of the glaciers around the GIS and the ice streams within it. Anyone? ”

    please see:Rignot et al., Science, 311, 2006.

    For similar map of Antarctica, Rignot et al. Science, 297, 2002.
    For Antarctica without ice
    http://commons.wikimedia.org/wiki/Image:AntarcticaRockSurface.jpg
    ICESAT rendition of Antarctic ice surface:
    http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16758

    sidd

    sidd

    Comment by sidd — 31 Oct 2007 @ 12:11 PM

  187. re #178

    Timothy

    I quote:

    “Oh, and sidd was comparing 1993-6 to 2003-6. 2 mm/y vs 4 mm/y. The rate has accelerated.”

    the sea level rise was 2.2 mm/y in 1993-1996 and 3.3 mm/y in 2003-2006.

    So we must not exagerate.

    And If I “choose” the 4 years precedent period (1999-2002) I find 4.6mm/y.
    So what is your opinion between 1999-2002 and 2003-2006?

    My position is always that there is no acceleration in the last ten years.
    It’s a fact.

    But rather to quibble about this evidence, it’s more interesting, I think, to ask oneself: why?

    My assumption is that the ocean cooling, found by Lyman(2006) for 2003-2005, is real, even if the amplitude of this cooling is too high.
    You can observe, after the rectification of Lyman 2006, that there is, at best, a stabilization of 0-750m temperature anomaly.
    I don’t repeat, for the Xth time, that SST are decreasing since 2003, but it’s also a fact.

    This little cooling or stabilization compensates the loss of ice of our prefered ice sheets.

    Another question is: why such an ocean cooling?

    Comment by Pascal — 31 Oct 2007 @ 1:00 PM

  188. Well, somehow these threads always turn to sea level rise predictions. How quickly will Greenland’s land surface rebound as it loses its ice? How quickly does the ocean basin respond to increased water weights (ocean basin deepening)? Do these crust/mantle processes occur on similar time frames or does rebound outstrip basin deepening? Can we consider the ocean basin volume as static for the purpose of sea level change prediction because the speed of water inputs will far outstrip the speed of mantle movements? And I’m totally confused on this point: is there a loss of ocean basin volume as the below sea level bed of Greenland rises up and displaces it? Maybe just answer this: Are the geologic models that predict the wishy washy flows of the earth’s mantle accurate or are there additional degrees of uncertainty in sea level rise estimates due to unknown continental and oceanic crust/mantle reaction times and magnitudes? You do have to be a rocket scientist to get this all down. BTW: Timothy translated Dr. Hansen’s possible “several” meters of potential sea level rise as 5 meters. I choose to believe several translates as 4 meters as my home and another 40,000 plus homes in Galveston County will only be under during spring tides at 4 meters whereas 5 puts the home in the big pool all the time.

    Comment by Andrew Sipocz — 31 Oct 2007 @ 1:02 PM

  189. RE 188: I live on the coast of Maine, where during the last glaciation there was a two mile thick layer of ice. The ice melted faster than the geostatic rebound and the area was subsequently submerged under about 200 feet of ocean. The land eventually rose and we are now about 50 feet above sea level.

    Comment by B Buckner — 31 Oct 2007 @ 1:39 PM

  190. Pascal Says at 31 October 2007, 1:00 PM:

    “the sea level rise was 2.2 mm/y in 1993-1996 and 3.3 mm/y in 2003-2006″
    1)what are the error bars on this result ?
    2)may i ask where these numbers from? the graph you posted earlier has no attribution.

    i use data from
    http://podaac.jpl.nasa.gov/DATA_PRODUCT/OST/index.html#jason. i obtain 2 mm/yr +/-0.2 mm/yr for 1993-6 and 4 +/- 0.2 mm for the 2003-6 period. the latter estimate agrees with Abdalati, Pg 10 http://www.laseagrant.org/forum/docs/03-20-07/WaleedAbdalati.pdf
    as well as with Lombard et al.Lombard et al,Earth and Planetary Science Letters, 254, 2007. With regard to the period 2003-2006 i quote directly from page 200 of the Lombard eta al. “…the Jason-1 sea level curve rises by 4.0+/-0.4 mm/yr. ” For the period 2002-2006 they go on to give a value of 3.1 +/- 0.2 mm/yr. which is closer to your estimate for 2003-2006. So it seems that your source is not quite in agreement with mine, and so i would be most interested to see the data or publication from which your graph derives.

    sidd

    Comment by sidd — 31 Oct 2007 @ 1:46 PM

  191. Is climate science becoming a gloom contest now? My understanding is, that Greenland and Antarctica iceshields are actually warmest at their base where they’re being warmed by the earth. Sliding ice is a geothermal effect – never an atmospherical and has nothing to do with global warming. Most of the shield itself is way below freezing point and won’t melt in a couple of millenia. Melting occurs on the edges and any percipitation in the center regions will accumulate and cause the shield to grow. I think its false to assume, that meltwater from the edges or the surface can penetrate deep into (and under) the very cold ice body and cause it to just swim away.

    Comment by henning — 31 Oct 2007 @ 2:00 PM

  192. OK, so it looks that we have a number of candidates for estimating GIMBI.

    It really is not a bad measure to keep the mind concentrated and for the layman it is a number which requires no thought.

    So TimothyChase wants to re-base 2050 to 1,5m : no problem with that, but for GIMBI we need to have a nice, good looking number, like 1000.

    So 1000 equals 1,5m. OK

    What about the Group, or Mr Hansen for that matter?

    The Group could put the GIMBI on the home page so all can see it with their coffee and croissants in the morning.

    Incidentally I am not at all depressed about the future : worried but not depressed.

    Comment by Eachran — 31 Oct 2007 @ 2:04 PM

  193. RE 160
    We do not need 6C rise in atmospheric temperatures to trigger ice sheet collapse. All we need is enough heat in the oceans, and a mechanism to transfer heat from the ocean to the ice. Rain works.

    Last summer, stationary “cyclonic” storms setup on the edge of the Arctic Sea ice (July) and the east coast of Greenland (June), apparently driven by the temperature differential between the open seawater and the ice. (They are clearly visible on the satellite photos, but I have not seen anything about them by weathermen and climate experts.) Thus, there is enough heat in seawater adjacent to NH ice to drive heat transfer mechanisms. Less ice on the Arctic Ocean is likely to intensify these mechanisms.

    The first question is: How long would it take to transfer enough energy to the Greenland Ice Sheet – not to melt it, but to weaken it so that sections of it collapse under their own weight, and potential energy is converted to kinetic energy? That is a very different question from the IPCC assumptions of Greenland Ice sheet melting in place. (Last summer’s ice surge observations may not “prove” anything to the scientist, but they suggest things to the prudent engineer.)

    In Hansen, 2005, he talks about the use of the word “explosive” in relationship to ice sheet collapse. I would disagree. “Explosive” implies material moving at supersonic speeds. Ice collapse is a sub-sonic process. However, since ice collapse is driven by water with a potentially large head (pressure), material can reach terminal velocity very rapidly.

    It is worth looking at the Lake Missoula floods in Washington State for what can occur. While the Missoula floods are normally presented as a failure of an ice dam on the Clark River, the nature of ice dams on rivers results in Lake Missoula having a significant sub-glacial character. (See the USACOE pages on river ice.) And, similar channels in Antarctica show that discharges from sub-glacial lakes can have similar erosion features. “Potholes” is worth walking, and easier to get to than Antarctica.

    The Lake Missoula floods moved large volumes of ice, hundreds of miles across a downgrade of only 2 or 3 %. And, they occurred not once, but time after time. Was it explosive? No! It only went 40 miles per hour.

    Certainly the basement rock in Greenland is relatively flat. However,the thickness of the ice sheet itself provides enough height to provide potential energy for at least a partial collapse process. I am aware of modeling of the profile of the Greenland Ice Sheet that suggests that the ice will melt to a shape that is stable. However, these models seem to ignore the formation of moulins and more importantly, rain. They seem to assume that there will be ice on the Arctic Ocean. That is no longer a valid assumption for a risk assessment.

    The second questions is: When will ocean water with a temperature of above 0C contact the base of the WAIS? Again the ice sheet does not need to melt in place for sea level rise to occur. All we need is enough heat to soften the foundation of the ice, so that the ice collapses into the sea under its own weight. Much less heat is required to soften the foundation, than to melt the body of the ice. Therefore, less time is required to transfer the heat.

    The IPCC Summary for Policy Makers provides unwarranted comfort.

    Comment by Aaron Lewis — 31 Oct 2007 @ 2:18 PM

  194. Henning, what’s your source for your information? Why do you believe it’s true? You’re using almost exactly the words just published by the inimitable Benny Peiser in his newsletter. Have you read his source?

    Comment by Hank Roberts — 31 Oct 2007 @ 2:29 PM

  195. Hank Roberts (#184) wrote:

    Tim Chase — there’s a noun wrong in this bit:
    (#173)
    “we will be running out of glaciers – which appear to be responsible for more melt than that due to glaciers.”

    Fixed it in 175:

    The italicized sentence should be “But it also doesn’t take into account the fact that we will be running out of glaciers – which currently appear to be responsible for more melt than that due to ice sheets.”

    Hank Roberts (#184) wrote:

    Re this

    “PS I gave Hank and Stefan a hard time … being tongue-in-cheek.”

    It’s hard to tell at best what the writer was feeling, there’s no emotional tone in ASCII except the reader’s projection, and as you said in a slightly different context “

    Humour. (I’m told mine is dry.) Affection. (But I prefer not to be obvious.)

    Despite the fact that this is all text, I like to think that I can read people and get to know their characters — and know when they are special human beings. And that matters to me.

    Comment by Timothy Chase — 31 Oct 2007 @ 2:35 PM

  196. sidd

    re#190

    my source is Univ of Colorado

    http://sealevel.colorado.edu/results.php

    and for the data this file:

    http://sealevel.colorado.edu/current/sl_noib_ns_global.txt

    Comment by Pascal — 31 Oct 2007 @ 2:37 PM

  197. Here is:

    ” a computer model depicting changes in the Antarctic ice sheet since the peak of the last ice age nearly 20,000 years ago. The West Antarctic ice sheet has lost nearly two-thirds of its mass during this period, a volume sufficient to raise sea level 33 feet (10 m).”
    http://www.mos.org/soti/icecore/
    http://www.mos.org/soti/icecore/images/AntChange2.mov

    Comment by Hank Roberts — 31 Oct 2007 @ 2:41 PM

  198. People will tell you the Antarctic ice can melt only on the edge.
    This popped up just recently in Benny Peiser’s newsletter and is making the rounds.

    You can look this stuff up if you’re practicing to become skeptical about what people tell you.

    For example, from tossing a few likely search terms at Google and perusing the first few dozen hits:
    http://www.jpl.nasa.gov/releases/2001/borehole.html

    —–excerpt——-
    March 16, 2001
    ICE PROBE REVEALS FIRST-EVER IMAGES DEEP WITHIN ANTARCTIC STREAMS

    Scientists have had their first inside look at ice layers, frozen debris and a surprising channel of water deep beneath an Antarctic ice stream, thanks to an ice probe designed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

    Plunged more than 1,200 meters (more than 3,900 feet) down four boreholes drilled in the West Antarctic ice sheet …..
    ….
    Equipped with two cameras and lights, JPL’s ice probe revealed what appears to be a basal water system, or series of water channels at the base of the ice stream. In places, this water-filled cavity measured approximately 1.4 meters deep (4.6 feet). Based on previous calculations, researchers expected the depth of a water basal cavity to be only in the millimeter range…..
    ——end excerpt——-

    There’s more to be found if you check what people tell you.

    Comment by Hank Roberts — 31 Oct 2007 @ 2:50 PM

  199. See also:
    http://skua.gps.caltech.edu/hermann/upc/pressrelease.html

    “UNEXPECTED BASAL CONDITIONS UNDER ANTARCTIC ICE STREAM C DISCOVERED WITH A NEW BOREHOLE VIDEO PROBE

    Barclay Kamb and Hermann Engelhardt (Caltech),
    Frank Carsey, Lonne Lane, and Alberto Behar (JPL)

    In a recent study of Anarcticas Ice Stream C, a joint NSF-NASA research team has discovered a surprising gap between the base of the ice stream and the rock below. The gap is up to 1.4 m (60 inches) wide, and is filled with water at a pressure nearly high enough to lift the ice stream off its bed. The discovery is significant in relation to the mechanism for rapid movement of the ice streams, which are huge, fast-flowing ice currents within the slow-moving ice sheet that covers most of Antarctica. The mechanism for their rapid movement is being intensively studied because of the possibility that rapid ice-stream flow may cause the ice sheet to disintegrate, resulting in a disastrous rise in world-wide sea level. …”

    Comment by Hank Roberts — 31 Oct 2007 @ 2:52 PM

  200. Aaron Lewis (139) — Well stated. A minor point is that the maximum flow rate of the Bretz (Missoula, Spokane) floods was almost 130 km/h (80 mph), from the Wikipedia article.

    With regard to sea stand rise with 3C global warming, I opine that 15 meters, plus whatever contribution from the melting of the Patagonia ice caps, Tibetan and other glaciers, is it. I doubt this would be significantly higher even at 6C global warming as the EAIS is under extremely cold air so that the warming would have little effect. But I’m only an amateur at this.

    Comment by David B. Benson — 31 Oct 2007 @ 3:22 PM

  201. And more, continuing to look up the claims that icecap ice only melts at the edge, from Benny Peiser’s latest newsletter.

    Wrong.

    Dr. Peiser seems not to be looking before publishing.
    That’s regrettable practice by an editor, seems to me as a reader.
    It means I need to check every claim I find in what he publishes.

    Good practice to developing healthy skepticism, of course.

    This is from 2001.
    http://www.aad.gov.au/Asset/magazine/2007-12/28AMISOR.pdf

    —–excerpt—–
    “The Amery Ice Shelf Ocean Research
    (AMISOR) project is part of a broad
    umbrella study of the entire Lambert
    Glacier Basin, Amery Ice Shelf system
    (located between Mawson and Davis in
    East Antarctica), to understand both the
    climatic history of the region, and its
    probable response to global warming.
    The project is part of the Australian
    Antarctic Division’s Ice, Ocean,
    Atmosphere and Climate programme and
    the Sea Level Rise programme within
    the Antarctic Climate and Ecosystems
    Cooperative Research Centre.

    “… the [biological] community beneath AM01 is
    indistinguishable from that commonly
    found on the Antarctic continental shelf in open
    water. Before now, if palaeontologists had found
    the fossil remains of such a complex community
    of organisms, they would probably assume that
    the site was free of the ice shelf when these
    animals were living there. Although a reasonable
    assumption, it turns out to be incorrect…..

    …. Another intriguing discovery of the AMISOR
    project has been the porous nature of the marine
    ice toward the base of the ice shelf at sites AM01
    and AM04. This feature manifested itself during
    the drilling process when a pressure sensor in the
    well indicated that hydraulic connection with the
    ocean cavity had been achieved whilst the drill
    head was still many tens of metres above the true
    base of the shelf.

    Borehole video footage showed that the lower
    70-100 m of the marine ice was honeycomb in nature
    with ice platelets (large ice crystals) welded together,
    and interstitial sea water filling progressively larger
    and larger cavities. The ability of sea water to move
    relatively freely through this honeycomb ice makes
    these parts of the shelf vulnerable to any increases
    in sea water temperatures…. ”

    ——- end excerpt ——-

    Comment by Hank Roberts — 31 Oct 2007 @ 3:28 PM

  202. Re. henning, #167, no new technologies are needed. All that is needed is political will. In Germany there is a fair amount of political will. Outside Germany, for the most part, there is not. Germany is reducing its emissions, while in the world as a whole, emissions are accelerating rapidly.

    I don’t know where you get the idea from that anyone here thinks that AR4 means nothing. I have not read a single post here to that effect. AR4 specifically excluded Greenland and Antarctica ice sheet melting, due to the uncertainties about ice flow dynamics, and also specifically excluded slow feedbacks, also due to the uncertainties involved. Pointing this out, and discussing the likely implications of that, in the light of the observed data, is hardly a reason to “demand one’s money back from the IPCC”, as you appear to be claiming it is. The IPCC was quite honest and upfront about this.

    The idea (quoted in the United Nations Environmental Programme report) that in order to be reasonably sure of avoiding dangerous and potentially irreversible climate change, a minimum of a 50% cut in global emissions compared with 1990 levels is required by 2050, is based firmly on the IPCC-led consensus, contrary to the impression you appear to have. In fact the British government regards the 50% figure as too low.

    You’ve also misread the implications what has been said here about Roe/Baker. Everyone (more or less) who has posted would agree with the IPCC’s “best guess” of 3 degrees C for climate sensitivity, and with it’s likely range of 2-4.5 degrees C. However, an insurance company does not insure only against likely risks; and and nor do sensible policy makers. To point that out is not exaggeration, as you claim, it is simply sound business practice.

    Comment by Dave Rado — 31 Oct 2007 @ 3:32 PM

  203. Re. henning, #191, as Hank says, please cite your peer reviewed sources.

    Comment by Dave Rado — 31 Oct 2007 @ 3:41 PM

  204. Re 191
    Henning, I had an ice field slide out from under my feet a couple of years ago. It had been there for generations. It slid on melt water from atmospheric warmth.

    I would encourage you to take up ice climbing and go “rub your nose” against a few thousand vertical feet of ice per year. Ice climbing is better than rock climbing. Ice is always changing and interesting. Ice climbing teaches you to get up early and climb while the ice is cold and hard, because it softens and weakens fast when the heat of the day hits it. But mostly, ice climbing teaches you to stay off the ice when it is raining, because the ice tends to slid downhill — suddenly.

    Certainly, I have never climbed the big ice sheets, but I have rubbed my nose on a fair bit of ice, and learned few lessons. One of those lessons is that flowing water moves heat a lot faster than stationary rock.

    Comment by Aaron Lewis — 31 Oct 2007 @ 3:45 PM

  205. sidd @186: thank you for those maps etc.

    henning @191: when you say “Sliding ice is a geothermal effect – never an atmospherical and has nothing to do with global warming”: I’m doubtful. The Greenland experts speaking to the media at the Ilulissaq meeting said that the major coastal glaciers are accelerating due to the lubrication by melt-water, reaching the basement from surface melt through an unprecedented number of moulins. The surface melt is of course due to global warming, and also due to arctic sea ice loss (which is at least partly an effect of global warming).

    If, as seems likely, the arctic sea ice loss worsens in coming summers, we will get rain in increasing amounts on increasingly large areas of Greenland. That’s not going to improve things: not all precipitation on an ice sheet is good!

    I think sidd and others (e.g. Aaron Lewis @ 193) might be erring on the alarmist side with talk of (e.g.) sustained 40mph ice movement. But I don’t think it’s reasonable to expect “business as usual” in an ice sheet subjected to sudden temperature increases and rain.

    Comment by Nick Barnes — 31 Oct 2007 @ 3:46 PM

  206. PS to Tim Chase — I too like to believe I can get to know people online, and be clever, but in public some later reader will always find in the ASCII their own feelings and project them. Much studied:

    http://www.csmonitor.com/2006/0515/p13s01-stct.html
    “One strategy: Read it aloud in the opposite way you intend, whether serious or sarcastic. If it makes sense either way, revise….”

    Another thought on this, addressed to the Contributors, the same article notes: “the pitfalls of e-mail interaction were easily overcome by a single phone call.”

    I’d suggest considering putting small video clips, perhaps of you answering one FAQ in your area or saying why you care about what you’re doing. The new generation relies on video, enormously, and this research really says clearly, good video can help nonscientists believe you’re credible:

    “SCIENCE NEWS October 23, 2007
    How to Win an Election: Make a Good First Impression (in Less than 250 Milliseconds)
    ——excerpt——–
    “All of the action goes on in the first 250 milliseconds of exposure, and then there’s not much going on,” says Alexander Todorov, an assistant professor of psychology and co-author of the study, which appeared in Proceedings of National Academy of Sciences USA, noting that these 250-millisecond trials yielded the greatest predictive success….”
    ——-end excerpt——–

    Scientists work by text and have a lot more buffering against emotional meltdown than ordinary readers like those of us here, trying to understand the science. Y’all are doing great. A little help for the ASCII/text with a phone call or video might go far.

    Pardon the digression. Icecaps and emotions can both melt down from inside and underneath as well as from contact at the edges, that’s the connection (grin).

    Comment by Hank Roberts — 31 Oct 2007 @ 3:50 PM

  207. RE #191 & “Greenland and Antarctica iceshields are actually warmest at their base where they’re being warmed by the earth”…

    Sounds quite logical and plausible to a layperson like me, not very savvy in the science. Only question is why didn’t it melt before, like 100 years ago, since it doesn’t need GW?

    Comment by Lynn Vincentnathan — 31 Oct 2007 @ 4:03 PM

  208. RE #193, are we talking about 2 things then, which are perhaps intertwined a bit?

    (1) One is the ice sheet and glacier mechanical collapse, which doesn’t require a whole lot more warming, but will happen with some set minimum amount of warming over some time period; and (2) the other is global warming that keeps increasing beyond the level needed to cause #1, which among other things will perhaps lead to positive carbon feedbacks (e.g., from melting permafrost and hydrates).

    Of course there are interrelations — I understand that a lot of energy (& heat) goes into melting ice, and the area (water, air) remains cool up until all/most the ice is melted, then the water and air are “free” to rise rapidly in temp to their new equilibrium (according to whatever the particular GW forces are). That’s what I’m envisioning now.

    Is it possible to have just this lower level of warming, just warm enough to melt most of the cryosphere (eventually), but not necessarily warm enough to set in motion a severe positive carbon feedback loop that takes us way up in warming for many thousands of years (like a hysteresis event). Or would melting of most of the cryosphere (given this input of just enough warming to cause that) ensure that we go into a long term extreme warming hysteresis event, leading to perhaps hydrogen sulfide outgassing and massive extinction?

    Comment by Lynn Vincentnathan — 31 Oct 2007 @ 4:31 PM

  209. http://www.bepress.com/ev/vol4/iss3/art3/

    The Berkeley Electronic Press
    Editor: Joseph Stiglitz, Columbia University

    The Economists’ Voice
    Special Issue: Global Climate Change
    Special Editor: Lawrence H. Goulder, Stanford University
    ….
    Climate Change: The Uncertainties, the Certainties and What They Imply About Action
    Thomas C. Schelling

    Comment by Hank Roberts — 31 Oct 2007 @ 4:36 PM

  210. Re: #193 Extratropical Storm Noel from the National Hurricane Center Web Page

    http://www.nhc.noaa.gov/refresh/graphics_at1+shtml/203525.shtml?5day#contents

    This is going to bring a lot of rain to the Greenland Ice Sheet. What if total tropical cyclone energy in the North Atlantic does increase greatly with AGW as some believe? Anyone know the amount of rain these things bring to the Greenland coast? What about the interior? Lots of snow or rain? Regular dousings of 5 or 10 inches of rain onto the GIce Sheet might change things relatively rapidly.

    Comment by Andrew Sipocz — 31 Oct 2007 @ 4:59 PM

  211. Nick Barnes Says at 31 October 2007, 3:46 PM

    “sidd @186: thank you for those maps etc.”

    you are most welcome.

    “I think sidd and others (e.g. Aaron Lewis @ 193) might be erring on the alarmist side with talk of (e.g.) sustained 40mph ice movement.”

    i am afraid that you must credit Mr. Lewis with the Missoula metaphor.

    I do want to expand a little on another point he made. When i began to look at mass and heat flow in and out of ice sheets, i assumed that flows in the ocean would be responsible for most of the heat, since water has a heat capacity almost a thousand times that of air. But, we live in a temperature range around the triple point, and the ocean (being much cleverer than i) has discovered a way to put heat into the ice that i had not seriously considered: rain. 540 cal/gm + 80 cal/gm is a serious multiplier. Thank you Mr. Lewis.

    sidd

    Comment by sidd — 31 Oct 2007 @ 5:47 PM

  212. Eachran (#192) wrote:

    So TimothyChase wants to re-base 2050 to 1,5m : no problem with that, but for GIMBI we need to have a nice, good looking number, like 1000.

    I might think that 1.5 m by 2050 is possible, I wouldn’t even be surprised if we get something above this, particularly after having read what Aaron Lewis had to say (193), but the formula was being applied to 2100 in the article with 95 cm being the midpoint of one standard deviation. And it still assumes things go linear. Aaron is suggesting that things won’t.

    My opinion?

    The formula (173) fits the data we have to date. I suspect that it will continue to do so for a while.

    How long? Hard to say.

    But I am not an expert, so even if I had an opinion — beyond the view that by the end of the century 5 m might be more realistic (the doubling-per-decade figure Hansen has spoken of — which is itself a guess, albeit with some support) — it really wouldn’t count for much of anything. But personally throwing out a number on a complete whim in the form of a “bet” makes me uncomfortable — given what I take those numbers to imply.

    Comment by Timothy Chase — 31 Oct 2007 @ 8:07 PM

  213. #174
    Lynn – thanks for your response – indeed if you talk about millenia, then indeed the scenarios are meaningful and indeed sea level could rise by 80m. But this has happened before and if we followed the historic warming / cooling cycles over previous millenia, then it would not have been unreasonable for sea-level to drop by 120m then rise again …. thats the cycle we are in.

    I’m still curious though – and have not had any good answer – sea-level is a function of global temperature. Since the 2001 IPCC report significantly overestimated T rise (current global temepratures are below the entire envelope !!), why do you have any faith in the 2007 report ?

    Comment by Imran Can — 1 Nov 2007 @ 3:31 AM

  214. I was just quoting textbook stuff – and I certainly don’t need a peer-reviwed article to know that water will melt around 0C and certainly not at -20C . Works about geothermal influences on the ice sheets and their internal structures have been around for some time. Very recently Adalgeirsdottir (and Dahl-Jensen?) concluded from magnetic satellite measurements that the heat fluxes below the ice are anything but uniformal and (should) have a major effect on ice modelling in the future.
    Surface temperatures, let alone those of the ice body itself, never come close to 0C in Antarctica and barely ever reach 0C on the Greenland sheet. So how can melting have an effect on the body? On the other hand, all the snow falling on top of the sheet accumulates. As long as there is more accumulation than melting on the edges, the mass grows and the resulting effect on sea-level is negative. Doesn’t AR4 list a negative sea-level effect of Antarctica for that very reason?
    The idea of a warming so huge and so rapid that it could melt away substancial parts of the Greenland or Antyarctica bodies in a couple of decades is pure alarmism. – as is the idea of the Greenland and Antarctica bodies sliding into the sea on an flow of meltwater. Living in the Alps I have experienced things like this myself. But we’re not talking about a couple of meters of ice on the slope of a mountain in spring time.

    Comment by henning — 1 Nov 2007 @ 4:43 AM

  215. James Annan has now responded in his blog, and is not at all impressed with the Roe and Baker paper.

    Comment by Dave Rado — 1 Nov 2007 @ 5:11 AM

  216. A point about sea-level: in this discussion (off topic), many consider that recent and short term trends measured by T-P or Jason can be extrapolated to the whole 21st century, and some even sugest an exponential rise.

    But decadal variablity in sea-level rise is the rule. For example, Holgate 2007 finds a +5,31 mm/y rate centered on 1980, more than the recent 4mm/yr.
    http://www.agu.org/pubs/crossref/2007/2006GL028492.shtml

    See also Jevrejeva 2006 on the same topics (non-linear trends in sea-level rise):
    http://www.agu.org/pubs/crossref/2006/2005JC003229.shtml

    The same is true for one source of sea-level rise, Greenland melting measured by GRACE : GRACE is a new instrument demanding calibration and Greenland a region known for its marked pluridecadal variability. So it seems a climatological non-sense to suppose that a 6 or even 10 years trend is a firm basis for a 100 years estimate.

    This does not mean that Greenland will not continue to melt (it will very probably on long term) and sea-level wil not continue to rise (idem).

    (Many will consider that as evident in other situations: when a skeptic says surface or low tropopshere temperature of the last 6 years has a modest slope if any, for example, they will promptly object that such a phenmenon is common and is due to the residual natural variability hiding for some years the anthropogenic forcing. So let’s be coherent with this attitude).

    Comment by Charles Muller — 1 Nov 2007 @ 5:34 AM

  217. #214, you bring up another very important issue here. While it seems Roe and Baker leave out the more external feedbacks (like the carbon issue & melting permafrost, etc), we others addressing those factors are pretty much holding the sun & its radiation constant.

    I’m thinking that if solar irradiation starts increasing (due to orbital factors or whatever) that could make matters REALLY bad, added on top of our anthropogenic forcing.

    (& BTW I think the reason we haven’t yet felt the full force of our GHG emissions being translated into warming is because of the short-term cooling effect of aerosols emitted while emitting CO2, the ocean inertia (a watched pot never boils effect), and other such factors (maybe the energy going into melting ice rather than directly into heat), and such.)

    So it extremely behooves us to reduce our GHG emissions very drastically very quickly…just in case the solar output starts increasing, adding heat on top of our anthropogenic global warming.

    Are there any other certain uncertainties we’ve missed?

    [Response: Just to be very clear, "orbital factors" aren't going to change on anything other than, well ... orbital timescales. That's tens of thousands of years, and not an immediate worry! As for the sun itself getting "hotter" suddenly, there's is no much evidence it has been all that much stronger, or weaker, in the past. It has changed, certaintly, but GHG forcing by humans greatly outweighs it's importance. --eric]

    Comment by Lynn Vincentnathan — 1 Nov 2007 @ 7:04 AM

  218. Oh, yeh….what if the sunshine decreases and it starts getting cooler (despite all our AGW).

    We really should stop using fossil fuels right this minute. We’ll need them once it gets really cold.

    So I can’t think of any argument at all to continue using fossil fuels (certainly at the rate we are using them), esp since we have better and cheaper alternatives.

    Comment by Lynn Vincentnathan — 1 Nov 2007 @ 7:08 AM

  219. Henning, re 214., have you looked at the heat fluxes they are talking about? They are of order mW per square meter. Not negligible to be sure, but not of the same order of magnitude as sunlight, etc. Ice dynamics is not a simple subject. It is one of the most uncertain as we try to estimate sea level rise. Heat can be transported by a veriety of methods, including meltwater.
    The facts are that the ice balance is negative. Most of the uncertainties lead to increased melting, rather than decreased, and the effects could be quite nonlinear.

    Comment by Ray Ladbury — 1 Nov 2007 @ 7:32 AM

  220. henning writes:

    [[ Sliding ice is a geothermal effect - never an atmospherical and has nothing to do with global warming.]]

    Warm air melts ice. And do a google search for the term “moulin.”

    Comment by Barton Paul Levenson — 1 Nov 2007 @ 8:17 AM

  221. Re: #116 David, thanks for the clarification regarding the graph and the probability density functions. Being a non-professional in these areas, I really appreciate it!

    Comment by Anders Lundqvist — 1 Nov 2007 @ 8:24 AM

  222. Despite the small amounts of energy involved, I thought that i.e. the Greenland boreholes showed more than 20 degree warmer temperatures at bedrock than at the surface, which cannot be explained by climatic influences. Doesn’t that support the theory of flow being primarily lubricated by geothermal influence rather than meltwater – especially in the center regions where there are less cracks in the ice and less melting at the surface during the summer (if any)? I agree with the opinion that little seems to be known about the effects ultimately determining why and how the sheets behave the way they do. Many aspects are obviously just beginning to surface (like the variety in geothermal flux mentioned above).

    Comment by henning — 1 Nov 2007 @ 9:07 AM

  223. Citizens of the US can add another certainty besides death and taxes. After reading Chris Mooney’s article in the November-December 2007 issue of the Bulletin of the Atomic Scientists”, titled “An Inconvenient Assessment”, we can be sure that no meaningful steps will be taken on AGW before January 2009. This an eye opening revelation of the lengths that conservative think tanks, with the help of the highest echelons of the White Hosue along with some in the Congress, will go to supress good scientific information and keep the public from hearing what the fossil fuel interests don’t want us to hear.

    The article deals with the supression of the National Assessment ( it’s official title is “Climate Change Impacts on the United States:The Potential Consequences of Climate Variability and Change”) by a lawsuit against it initiated by Sen. James Imhofe,of Oklahoma, which tried to prevent the Report from being released. He was supported by The Conservative Enterprise Institute and others in Congress. Bush himself sneered that it was something prepared by “the bureaucracy”. But the National Academy of Sciences endorsed it and used it.The web site of The Bulletin is: http://www.thebulletin.org though the site still shows the September-October issue as the latest issue, as of this morning.

    In addition there’s an article by Bill McKibben dealing with climate change, and an interview of Brice Smith who speaks about the high risk consequences of using nuclear power as a substitute for fossil fuels.

    Comment by Lawrence Brown — 1 Nov 2007 @ 10:05 AM

  224. Re # 187 Pascal

    What makes you think the ocean has been cooling?

    http://www.realclimate.org/index.php/archives/2007/04/ocean-cooling-not/

    Comment by Chuck Booth — 1 Nov 2007 @ 11:38 AM

  225. As incredibly intelligent humans are we have one genetic (I am NOT going to say flaw) shortcoming that actually is the root of global warming, that is our genes have no built in “governor” shall I say that lets us know when enough is enough. Our genes want us to survive, and will keep on reproducing without any sensible or chemical constraints on the issue. Furthermore, we subordinate ourselves to this decree in every way possible, even by having a real climate website no offense intended. For example, real climate contributers, lets take the responder of post number one here, eric, who believes post number one is a thoughtful intelligent post, which it is, and thus satisfies one crucial requirement of this website, that of enriching the minds of the contributers so they can perhaps advance the science. But this is merely satisfying a genetic command, of furthering the species at all costs. A scintillating response resonates well with the contributers and they may respond in kind. But let us not forget why this is all to be, a genetic decree to survive. Unfortunately, a genetic shortfall across the board in all human endeavors is we don’t have a command for “we have ideal numbers, lets stop production” gene that is ultimately our demise. This whole website fits into the genetic scheme, it is actually nothing more.

    Comment by PaulM — 1 Nov 2007 @ 12:10 PM

  226. Re 214

    A bit of soot on ice under sunlight allows melting to occur, even when the temperature is 0C. This can happen even when the air temperature a few cm above the ice is below freezing. This provides meltwater that can move through the ice tranfering heat.

    More importantly, the the surface temperature in Greenland has risen. In 1970, it was still possible to find old men that had lived on Greenland all their life and had never seen rain. Last year, rain was reported in every month of the year from somewhere in Greenland, and last summer, large swaths of the “interior” had significant rain events. With open water on both sides of Greenland in the summer, it is seeing more days when the temperature is above 0C.

    Comment by Aaron Lewis — 1 Nov 2007 @ 12:11 PM

  227. Gloom and Doom? Not at all!
    If this site was about gravity, we would say, Gravity is real and you must deal it! Do the necessary! Build your sky scraper strong enough to resist gravity and put big enough engines in your airplanes.”

    However, this site is about climate change. Our message is: “Climate change is real, and we need to deal with it.”

    We have not been showing the political will and engineering necessary to deal with climate change. We encourage people to do the necessary by reminding them that however onerous the “necessary” seems, failure to do the necessary is much worse.

    Comment by Aaron Lewis — 1 Nov 2007 @ 12:31 PM

  228. OK, I have read James Annan’s blog and written a reply but all I was asked for was google rubbish to verify something, so it wasnt posted. Never mind.

    I accept that the tail is a bit dodgy because I trust Mr Connelly and Mr Annan on the maths and if I wanted to challenge I would have to revise my stats for the next three months and I cant do that.

    The more important point is that the one known unknown is sea level rise : all the other IPCC stuff is OK by me apart from being at least a few years out of date.

    Is it not too much to ask someone somewhere to tell me what is their best guess of sea level rise by 2050?

    Let’s have a GIMBI.

    It would be a good way to bring science into the 21st century, dont you think?

    I dont think that Newton would have had a problem answering the question. And he wouldnt have started with : well Eachran there are too many uncertainties and this and that and the other and well I dont really know.

    What he would have said would have been probably something like : Eachran, X metres, now please go away and leave me alone to solve more important problems.

    Comment by Eachran — 1 Nov 2007 @ 1:03 PM

  229. River hydrology, water supply and vanishing glaciers: Regions of concern:

    Northwest China
    China’s glaciers that supply water to arid regions to vanish by 2100

    Himalaya and Tibet
    Himalayan glaciers that feed the seven great rivers of Asia are in retreat

    South American Andes and Kilimanjaro
    Kilimanjaro loses 1/4 of ice from 2000-2006; Andes melt rate increases 10X in 20 years

    European Alps
    All glaciers in the Alps likely to be gone by 2050

    Canadian Ice Cap
    Melting glaciers in Canada reveal pristine 7,000 yr-ol tree stumps

    Given that these melting rates are a response to current climate forcings, it seems fairly obvious that the glaciers will all melt, even if CO2 levels are stabilized at today’s levels. The climate system temperature hasn’t yet equilibrated to the current forcing, either – the estimate seems to be that there is about 0.6C of lag at present? More water vapor from a warming ocean, less precipitation in continental interiors, more precipitation in coastal zones, more precipitation as rain rather than as snow, drier soil and vegetation in an expanding subtropical dry zone – and that’s just under current conditions.

    What’s remarkable in the discussion about responses is how few people have tried to explain how we can replace 90% of the current energy generated globally with fossil fuels with renewables. From a policy perspective, nations, states and cities should really be coming up with realistic plans to deal with a scenario in which only 10% of existing fossil fuel-sourced energy is available. Renewable energy generation and management needs to be supported, and the use of fossil fuels needs to be discouraged in all areas – in industry, in agriculture, and in residential communities. Cosmetic measures are entirely inadequate. We need engineering-based solutions to the energy supply problem, and that will require a complete rethinking of global energy economics.

    Comment by Ike Solem — 1 Nov 2007 @ 1:31 PM

  230. chuck

    re 224

    look at this graph built with Hadley data

    http://www.host-img.com/visitors/1193941797.jpg

    (it is not 1198, but 1998, obviously)

    as NH land temperature goes up, the SH ocean (and global ocean) temperature goes down since about 2003.

    I don’t say this is a heavy trend but, at least, this phenomenon merits an explanation.

    No?

    For the correction of Lyman 2006, sorry but a graph, present in the draft, disappeared in the definitive version .

    Comment by Pascal — 1 Nov 2007 @ 1:40 PM

  231. Re 227. To say nothing of the fact that some of us, at least, believe that much of the “necessary” is not only not necessarily onerous but in fact desirable for reasons other than dealing with AGW.

    Comment by Mary C — 1 Nov 2007 @ 2:51 PM

  232. Pascal (#240) wrote:

    as NH land temperature goes up, the SH ocean (and global ocean) temperature goes down since about 2003.

    I don’t say this is a heavy trend but, at least, this phenomenon merits an explanation.

    And before 2003…? Your graph shows that they were moving in similar directions.

    Sure – the weak “counterintuitive” difference in trends might be something worth looking into. But it doesn’t change the overall trend of both over the past century towards higher temperatures.

    And I wouldn’t consider it a major mystery.

    We have warm El Ninos followed by cooler La Ninas, the North Atlantic Oscillation, the Pacific Decadal Oscillation, the Julian Oscillation, … When we want to refer to them as a whole, we will call it “internal variability.” Or maybe its aerosols from China’s economic ramp-up. Locally they enhance global warming, but globally they result in a cooling effect.

    What is involved here?

    Don’t know. I am not a climatologist. Might be interested in finding out, though. So when you solve this major mystery please let me know.

    Comment by Timothy Chase — 1 Nov 2007 @ 3:05 PM

  233. “Is it not too much to ask someone somewhere to tell me what is their best guess of sea level rise by 2050?” asks Eachran in #228
    Not at all Eachran- But before you take out the contour maps be aware that it’s an uneducated guess with the emphasis on guess,but if it puts me in the company of Newton, I’ll take a shot in the dark.

    For the number below to happen that more land ice will have to melt than is currently projected. However, it’s not just the absolute rise in sea level but the accompanying storm surges that would occur with any rise and the resultant flooding of all unprotected low lying lands,which are at higher elevations than the absolute rise. O.K. here goes- .4 meters( about one and 1/4 feet). I fervently hope I’m wrong and that we take steps that will avoid such a rise that will jeopardize millions of people in Bangladesh and other areas around the world.

    Comment by Lawrence Brown — 1 Nov 2007 @ 4:05 PM

  234. Why are glaciers melting a problem? (apart from sudden melts causing floods?)
    Surely its the precipitation/rain/snow annual input that finally limits the river-output.
    If precipitation increases then rivers & their peoples will be OK.
    If precipitation is irrelevant, how long have we been “Mining” these glaciers. Are glaciers then a non-renewable resource?

    Comment by g bruno — 1 Nov 2007 @ 6:49 PM

  235. Re #234: [Surely its the precipitation/rain/snow annual input that finally limits the river-output.]

    Glaciers (and snowpacks) tend to smooth out seasonal & annual variations in precipitation. For instance, here in northern Nevada most of the precipitation falls as snow in the Sierra. That snowpack melts gradually, often lasting into July, with bits at the higher elevations sometimes persisting all summer. However, it’s possible to get warm rains during the winter, if storm tracks move to the southwest. Enough of that warm rain and the snowpack melts, quite suddenly, and we get floods, then drought in summer.

    In a world without glaciers, you’d find this sort of thing happening much more often. Instead of dependable river flows, you’d see cycles of flood and drought.

    Comment by James — 1 Nov 2007 @ 10:52 PM

  236. g bruno – think that through a little more. If all the precipitation falls as rain in the spring, then what you have, instead of the development of a snowpack in the mountains (or on top of the glacier), is massive flooding in the spring, followed by a long dry summer and fall. Such events are already quite frequent.

    Millions try to rebuild lives after S.Asia floods, Sun Sep 2, 2007

    Chinese floods leave dozens dead, Sunday, 10 June 2007

    Record Flooding Hits Britain, June 2007

    So, what are we seeing here? Freak events or a consistent trend? The United Nation’s emergency relief coordinator, Sir John Holmes, has this to say:

    “We are seeing the effects of climate change. Any year can be a freak but the pattern looks pretty clear to be honest. That’s why we’re trying … to say, of course you’ve got to deal with mitigation of emissions, but this is here and now, this is with us already.”

    There are a number of different factors. First is that warmer air can hold more water vapor, leading to torrential rains in coastal regions that last longer than usual. The fact that wamer air can hold more water vapor is also leading to more drought in continental inland regions, since the soil water goes into the air, but there’s less precipitation (due to the warmer, but unsaturated, air).

    One might think that more precipitation would then lead to more snowfall in regions such as the Sierra Nevada, which gets air masses saturated with oceanic moisture, but with the increasing temperatures at altitude, the precipitation is as rain, or if as snow, doesn’t last as long.

    As far as the glaciers go, over the past thousands of years they appear to have been in steady state, more or less, with summer melt being made up by winter snowfall. The water resource that we’ve been mining has been groundwater, for example, the Ogallala reservoir of the US Midwest.

    So, what will happen to regions that depend on late summer snow-or-glacier-melt as their only source of water? Floods part of the year, and severe drought the other. This will of course play havoc with agriculture. Before anyone mentions it, it’s clear that dams are no solution to this problem.

    Comment by Ike Solem — 1 Nov 2007 @ 11:14 PM

  237. Ike Solem 229: “… how we can replace 90% of the current energy…”
    Good question – and surely the one thing almost everybody in almost all industries thinks about. Over here we’ve started taxing energy higher than ever before. Fuel is at 1.4 Euros per liter (almost 7.7 dollar/gallon). My new car does more than 50 miles/gallon as a result and the pressure to make electric cars that actually work becomes ever greater. This years motorshow in Frankfurt had not a single manufacturer who didn’t show at least a study of a purely electric or hydro powered car. It will take time but for the first time one had to get the impression that this wasn’t some exotic sample to keep the green party happy but a serious effort to fundamentally change the industry.
    Windmill power plants pop up everywhere – so many that they’re beginning to dominate the appearance of the country. And its hard not invest in them because its very good business. My electricity comes from renewables only (biomass, wind, water) not because I panic in the face of warming but because its cheap.
    What I’m trying to say here: It CAN be done and it WILL be done. Global economy will not pay ever rising prices for oil and just shut down when the final drop has been used. Politicians can try to cautiously speed up the process but they must not exaggerate. A lasting economic breakdown on top of the consequences from AGW, some of which we’ll have to face anyway, would be disastrous. So politics is confronted with a standard regulation problem. Keeping economy healthy and reducing GHG and deal with the consequences from warming and making sure they get re-elected and all that on a constrained budget. Not an easy task.

    Comment by henning — 2 Nov 2007 @ 2:56 AM

  238. RE #223 & “…no meaningful steps will be taken on AGW before January 2009…The article deals with the supression of the National Assessment…”

    I agree that it would be very helpful if our leaders were on board helping us mitigate GW, but there is tremendous amount individiuals and families can do and most responsibility rests with them.

    Also I think states have been putting out their own impact statements. I ordered and received the one from Illinois in the mid 1990s, which predicted (among other things) there would be more flooding in certain areas. I had it in hand when I told the head of the Public Opinion Lab (which had been severely flooded — a area which had never been flooded in known history) that it may have been caused by GW. She laughed in my face at the idea. I waved the manual in her face, saying even Gov. Jim Edgar had signed it.

    Still it would be nice if our leaders were on board.

    Comment by Lynn Vincentnathan — 2 Nov 2007 @ 9:07 AM

  239. Re #237: “This years motorshow in Frankfurt had not a single manufacturer who didn’t show at least a study of a purely electric or hydro powered car.”

    A hydro-powered car is something I’ve got to see!

    Seriously, I just checked in on this thread, and I’m glad to see that the authors recognize the implications of “precautionary policy” in the context of this kind of uncertainty.

    –Paul

    Comment by Paul Baer — 2 Nov 2007 @ 10:04 AM

  240. @Paul 239
    Forgive my Englisch. I meant to say “hydrogen”.

    Comment by henning — 2 Nov 2007 @ 11:50 AM

  241. Hydro powered cars may not exist but air-powered cars do, and strike me as a far better option that hydrogen. See here.

    Comment by Dave Rado — 2 Nov 2007 @ 2:51 PM

  242. In comment # 238 Lynn states:”…..it would be very helpful if our leaders were on board….there is tremendous amount individiuals and families can do and most responsibility rests with them.
    “Also I think states have been putting out their own impact statements. I ordered and received the one from Illinois in the mid 1990s……….”

    I definitely agree that all levels of government and groups and individuals can do a lot to reduce the releases of GH gases. The problem with this administration is that they are not only not aboard but they’re ramming the ship!

    Chris Mooney points to our friend from “An Inconvient Truth”, the lawyer, Philip Cooney, who edited many of the documents on climate for the White House and played the lead in enforcing the White House’s effort to suppress the National Assessment! His resume? Prior to his White House appointment he worked for the American Petroleum Institute and after it he went to work for (who else?) Exxon Mobil!

    The states have taken the initiative in this area, especially California, where an attempt to make mileage standards higher than the federal ones, and an attempt ot curb GHGs of power plants await decision in the courts.

    Fortunately the spirit of Eliot Ness lives on in the hearts( and guts) of career civil servants and those who like yourself,who have given yeoman service to this problem. They can’t be silenced, bought off or scared off by thuggish tactics. Yet, it would be nice if, the White House and their cohorts, at least if they don’t come aboard, would stop trying to sink the ship!

    Comment by Lawrence Brown — 2 Nov 2007 @ 3:51 PM

  243. RE #223 & “…no meaningful steps will be taken on AGW before January 2009…The article deals with the supression of the National Assessment…”

    I agree that it would be very helpful if our leaders were on board helping us mitigate GW, but there is tremendous amount individiuals and families can do and most responsibility rests with them.

    =================

    There is an arguement that a change of leadership doesn’t necessarily mean a change of direction.

    http://www.truthout.org/docs_2006/103107F.shtml

    To echo Lawrence Brown’s comments in 223, the problem is U.S. global security is predicated on keeping oil flowing to maintain the way of life that exists here. It’s been that way since the end of the second world war and I see nothing to suggest there is any sincere effort to deviate from that policy. And a policy of keeping oil flowing that includes boots on the ground means dissent is not welcome. Arguments to mitigate AGW invariably involve an ultimate reduction in the flow of oil. And as we’ve seen with the manner in which the current administration has approached the science of AGW, such arguments are apparently not welcome.

    I see nothing in the current crop of potential candidates that give me any reason for hope that American Global Policy will change any time soon, or that sincere efforts to address AGW will occur.

    Comment by J.S. McIntyre — 2 Nov 2007 @ 4:22 PM

  244. re: #236
    Yes, for sure, and the state planners here in CA worry about this all the time, as do the ski resorts. Arnold and the legislature may disagree about the solutions, but I think they agree the problem exists. [Unfortunately, we'll need conservation + (a few more, most of the good places are used) dams + downsize agriculture (probably)], and we’ll probably get by … but then, CA is fairly rich, and accustomed to dealing with disasters and trying to plan ahead, and not every place has those characteristics.

    More and more, I think the Evil Trio is Global Warming, Peak Oil, and Water, and I’m not sure of the priority. As Peak Oil hits (if it hasn’t already in 2006, as per T. Boone Pickens), massive engineering works for adaptation, like moving cities, or rebuilding levees in central CA, will be a lot more expensive without petroleum…

    As for leaders (Lynn), I keep reminding:

    “President Bush announced today that the United States has agreed with other industrialized nations that stabilization of carbon dioxide (CO2) emissions should be achieved as soon as possible.”

    http://www.presidency.ucsb.edu/ws/index.php?pid=17765

    That *was* 1989, but really, there are a fair number of leaders in various places who are trying. CA will sue the EPA shortly, and there are a bunch of other states with that.

    Comment by John Mashey — 2 Nov 2007 @ 6:22 PM

  245. @Dave 241
    This is way off topic, but the air car is one of those city-only-and-may-exist-some-time-in-the-future-never-mind-the-law-suits-filed-against-the-inventor efforts. Just search the web for Guy Negre. Hydrogen powered cars (internal combustion and fuel cell) are real today.

    Comment by henning — 3 Nov 2007 @ 5:35 AM

  246. Re 245: [Hydrogen powered cars (internal combustion and fuel cell) are real today.]

    More off-topic: Hydrogen powered cars are real. What’s unreal is a source of H2 that doesn’t produce more CO2 than the same car burning gasoline.

    If you want an efficient alternative, how about a grid-chargable hybrid, primary electric drive using a very efficient Stirling-cycle engine for long range? Possibly using high-speed flywheels instead of batteries?

    Comment by James — 3 Nov 2007 @ 11:27 AM

  247. When specifying desirable alternatives, remember:
    “If wishes were horses, then beggars would ride.”

    Pointing to specific existing technology rather than vaporware helps.

    Comment by Hank Roberts — 3 Nov 2007 @ 1:21 PM

  248. The populace in the United States of America are, in fact, doing something about global warming and climate change. A conference of mayors has just concluded in Seattle with more details about that and many other (small) steps being taken to be found on the U.S. Conference of Mayors web site:

    http://usmayors.org/uscm/home.asp

    Comment by David B. Benson — 3 Nov 2007 @ 1:59 PM

  249. Re. #247, Hank, I agree. IMO, Hydrogen as a viable alternative fuel is a red herring, because as James said, “what’s unreal is a source of H2 that doesn’t produce more CO2 than the same car burning gasoline.”

    But manufacturers could dramatically increase fuel efficiency on all new cars now, especially in the US. There’s no need to use alternative fuels in order to achieve efficiency gains of around 30% on average, only the political will is lacking. (See also here).

    For cars that are already on the road, emissions could be reduced by around 20% if strong financial incentives (grants and tax incentives) were given to convert to LPG .

    The price differential between hybrids and fossil fuel cars could be removed at a stroke if sales tax levels were set based on a car’s GHG emissions per mile, and this would be likely to make a huge difference to take-up of hybrids – again, the problem is not technology, it is simply lack of political will.

    Comment by Dave Rado — 3 Nov 2007 @ 2:04 PM

  250. I agree with you,J.S.( comment #243) that our leaders will continue to try to protect oil interests in the mid east.We’ve been playing up to them since President Rooosevelt courted favor with the Sheiks,Mullahs,Princes and Imams in the mid 1940s. But this only part of the supply side of the equation.

    This administration refuses to consider any caps on CO2 other than recommending voluntary measures. They’ve also been lax in proposing incentives for renewables. The fossil fuel industry is getting the lions’s share of subidies. For all of me, these current leaders have brought political interference on science to a new level. When James Hansen was interviewed on “60 minutes” he was accompanied by an appointed “escort”. This is over the top. Yeah, all administrations interfere to some extent, but not to such a degree.

    Then there’s the demand side of the equation. Efficiency and conservation are crucial elements to cutting GHG emissions by targets of up to 80% by 2050! Yet, we have a very influential Vice President who believes that conservation is as he puts it “a personal virtue”. The abuse of science won’t end after the next inauguration in 2009,but it’s bound to get better. I don’t see how it can get worse.

    Comment by Lawrence Brown — 3 Nov 2007 @ 7:01 PM

  251. A bunch of mayors sitting around drinking coffee having a conference while thousands of people in Mexico are trapped in a flood and two days rain in Haiti has washed poor people out of their shelters (homes) is exactly what is wrong with the present situation. Thanks for the U.S. Conference of Mayors website link, but as a member of the populace of the U.S., you Mayors should be ashamed of yourselves. Let me guess,how many Mayors weighed over 250 lbs. and had the gut the size of a foal? How many comfortable dinners did you have “conferring” while many many poor people are suffering? Having a conference is not doing something about global warming the populace says.

    Comment by PaulM — 3 Nov 2007 @ 7:06 PM

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