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The certainty of uncertainty

Filed under: — group @ 26 October 2007

A paper on climate sensitivity today in Science will no doubt see a great deal of press in the next few weeks. In “Why is climate sensitivity so unpredictable?”, Gerard Roe and Marcia Baker explore the origin of the range of climate sensitivities typically cited in the literature. In particular they seek to explain the characteristic shape of the distribution of estimated climate sensitivities. This distribution includes a long tail towards values much higher than the standard 2-4.5 degrees C change in temperature (for a doubling of CO2) commonly referred to.

In essence, what Roe and Baker show is that this characteristic shape arises from the non-linear relationship between the strength of climate feedbacks (f) and the resulting temperature response (deltaT), which is proportional to 1/(1-f). They show that this places a strong constraint on our ability to determine a specific “true” value of climate sensitivity, S. These results could well be taken to suggest that climate sensitivity is so uncertain as to be effectively unknowable. This would be quite wrong.

The IPCC Summary For Policymakers shows the graph below for a business-as-usual carbon emissions scenario, comparing temperatures in the 1980s with temperatures in the 2020s (orange) and 2090s (red). The latter period is roughly when CO2 will have doubled under this scenario. The resulting global temperature changes cluster between 2 and 5 degrees C, but with a non-zero probability of a small negative temperature change and long tail suggesting somewhat higher probabilities of a very high temperature change (up to 8 degrees is shown).

We have very strong evidence for the middle range of climate sensitivities cited by the IPCC. But what Roe and Baker emphasize is that ruling out very high sensitivites is very difficult because even the relatively small feedbacks, if they are highly uncertain, can have a very large impact on our ability to determine S.

Paleoclimate data do provide a means to constrain the tail on the distribution and perhaps to show the likelihood of large values of S is lower than Roe and Baker’s calculations suggest. In particular, 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 (see our post on this, here). Their result is a mean value of deltaT close to 3ºC, and a high probability that the sensitivity is less than 4.5ºC, for a doubling of CO2 above pre-industrial levels. Thus, we emphasize that Roe and Baker’s result do not really tell us that, for example, 11°C of global warming in the next century entury is any likelier than we have suggested previously.

On the other hand, there is a counterpoint to such a comforting result. Roe and Baker note that the extreme warmth of the Eocene — something that has stymied climate modelers — could in principle be explained by not-very-dramatic changes in the strengths of the feedbacks, again because small changes in f can produce dramatic change in S. The boundary conditions for Eocene climate remain too poorly known to include in a formal calculation of climate sensitivity, but at the very least the extreme climate of this time suggests that we cannot readily cut the tail off the probability distribution of S.

It would be wrong to think that climate scientists have been ignorant of the non-linear nature of feedbacks on climate sensitivity. Several papers dating back a couple of decades show essentially the same result (for example, Hansen et al., 1984; Schlesinger, 1988; see below for full citations). But Roe and Baker’s paper is probably the most succinct and accessible treatment of the subject to date, and is a timely reminder of some very basic points that are not always appreciated. For example, it is often assumed that the tail on the distribution of climate sensitivity is due to the large uncertainty in some feedbacks, particularly clouds. Roe and Baker make it very clear that this is not the case. (The tail in S results from the probability distribution of the feedback strengths, and unless those uncertainties are distributed very, very differently than the Gaussian distribution assumed by Roe and Baker, the tail will remain). Furthermore, they point out that “uncertainty” in the feedbacks need not mean “lack of knowledge” but may also reflect the complexity of the feedback processes themselves. That is to say, because the strength of the feedbacks are themselves variable, the true climate sensitivity (not just our ability to know what it is) is inherently uncertain.

What will get the most discussion in the popular press, of course, are the policy implications of Roe and Baker’s paper. Myles Allen and David Frame take a stab at this in their Perspective.* Their chief point is that it is probably a bad idea to assign a specific threshold value for CO2 concentrations in the atmosphere, above which “dangerous interference in the climate system” may result. 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°.

Allen and Frame suggest that the way to address this is though an adaptive climate change policy, in which there are movable CO2 concentration targets that can be revised downwards if future observations suggest that the climate sensitivity is indeed greater than the middle IPCC range. We agree that adaptive policies are needed. There is no point in continuing to pursue a 450 ppm stabilization goal in the eventuality that temperatures have already exceeded the expected 2 deg C. More reductions would be called for. Similarly, if temperature rises more slowly than expected, that would buy time. 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 — both of which are typically in short supply. If reactions to a worse-than-expected climate change are delayed, they make an overshoot of any temperature target very likely, and corrective action very expensive. Thus conservative strategies would seem in order, which probably implies initial targets of much lower than 450 ppm, and still subject to further revision.

The bottom line is that 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. This is something policy makers should recognize and confront.

Hansen, J.E., et al., in Climate Processes and Climate Sensitivity, J. E. Hansen, T. Takahashi, Eds. (Geophysical Monograph 29, American Geophysical Union, Washington, DC, 1984), pp. 130–163.
Schlesinger, M.E., 1988: Quantitative analysis of feedbacks in climate model simulations of CO2-induced warming. In Physically-Based Modelling and Simulation of Climate and Climatic Change, M. E. Schlesinger, Ed., NATO Advanced Study Institute Series, Kluwer, Dordrecht, 653-736.
*See also the news article in Nature. And our congratulations to Myles Allen and his colleagues who won the Euro Prix award for their work.

251 Responses to “The certainty of uncertainty”

  1. 201
    Hank Roberts says:

    And more, continuing to look up the claims that icecap ice only melts at the edge, from Benny Peiser’s latest newsletter.


    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.

    “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 ——-

  2. 202
    Dave Rado says:

    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.

  3. 203
    Dave Rado says:

    Re. henning, #191, as Hank says, please cite your peer reviewed sources.

  4. 204
    Aaron Lewis says:

    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.

  5. 205
    Nick Barnes says:

    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.

  6. 206
    Hank Roberts says:

    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:
    “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)
    “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).

  7. 207
    Lynn Vincentnathan says:

    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?

  8. 208
    Lynn Vincentnathan says:

    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?

  9. 209
    Hank Roberts says:

    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

  10. 210
    Andrew Sipocz says:

    Re: #193 Extratropical Storm Noel from the National Hurricane Center Web Page

    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.

  11. 211
    sidd says:

    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.


  12. 212
    Timothy Chase says:

    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.

  13. 213
    Imran Can says:

    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 ?

  14. 214
    henning says:

    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.

  15. 215
    Dave Rado says:

    James Annan has now responded in his blog, and is not at all impressed with the Roe and Baker paper.

  16. 216
    Charles Muller says:

    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.

    See also Jevrejeva 2006 on the same topics (non-linear trends in sea-level rise):

    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).

  17. 217
    Lynn Vincentnathan says:

    #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]

  18. 218
    Lynn Vincentnathan says:

    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.

  19. 219
    Ray Ladbury says:

    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.

  20. 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.”

  21. 221
    Anders Lundqvist says:

    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!

  22. 222
    henning says:

    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).

  23. 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: 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.

  24. 224
    Chuck Booth says:

    Re # 187 Pascal

    What makes you think the ocean has been cooling?

  25. 225
    PaulM says:

    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.

  26. 226
    Aaron Lewis says:

    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.

  27. 227
    Aaron Lewis says:

    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.

  28. 228
    Eachran says:

    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.

  29. 229
    Ike Solem says:

    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.

  30. 230
    Pascal says:


    re 224

    look at this graph built with Hadley data

    (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.


    For the correction of Lyman 2006, sorry but a graph, present in the draft, disappeared in the definitive version .

  31. 231
    Mary C says:

    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.

  32. 232
    Timothy Chase says:

    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.

  33. 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.

  34. 234
    g bruno says:

    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?

  35. 235
    James says:

    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.

  36. 236
    Ike Solem says:

    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.

  37. 237
    henning says:

    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.

  38. 238
    Lynn Vincentnathan says:

    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.

  39. 239
    Paul Baer says:

    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.


  40. 240
    henning says:

    @Paul 239
    Forgive my Englisch. I meant to say “hydrogen”.

  41. 241
    Dave Rado says:

    Hydro powered cars may not exist but air-powered cars do, and strike me as a far better option that hydrogen. See here.

  42. 242

    In comment # 238 Lynn states:”… 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!

  43. 243
    J.S. McIntyre says:

    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.

    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.

  44. 244
    John Mashey says:

    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.”

    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.

  45. 245
    henning says:

    @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.

  46. 246
    James says:

    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?

  47. 247
    Hank Roberts says:

    When specifying desirable alternatives, remember:
    “If wishes were horses, then beggars would ride.”

    Pointing to specific existing technology rather than vaporware helps.

  48. 248
    David B. Benson says:

    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:

  49. 249
    Dave Rado says:

    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.

  50. 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.