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The IPCC Fourth Assessment SPM

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We’ve had a policy of (mostly) not commenting on the various drafts, misquotes and mistaken readings of the Fourth Assessment report (“AR4” to those in the acronym loop) of the IPCC. Now that the summary for policy makers (or “SPM”) has actually been published though, we can discuss the substance of the report without having to worry that the details will change. This post will only be our first cut at talking about the whole report. We plan on going chapter by chapter, hopefully explaining the key issues and the remaining key uncertainties over the next few months. This report will be referenced repeatedly over the next few years, and so we can take the time to do a reasonable job explaining what’s in it and why.

First of all, given the science that has been done since the Third Assessment Report (“TAR”) of 2001 – much of which has been discussed here – no one should be surprised that AR4 comes to a stronger conclusion. In particular, the report concludes that human influences on climate are ‘very likely’ (> 90% chance) already detectable in observational record; increased from ‘likely’ (> 66% chance) in the TAR. Key results here include the simulations for the 20th Century by the latest state-of-the-art climate models which demonstrate that recent trends cannot be explained without including human-related increases in greenhouse gases, and consistent evidence for ocean heating, sea ice melting, glacier melting and ecosystem shifts. This makes the projections of larger continued changes ‘in the pipeline’ (particularly under “business as usual” scenarios) essentially indisputable.

Given all of the hoopla since the TAR, many of us were curious to see what the new report would have to say about paleoclimate reconstructions of the past 1000 years. Contrarians will no doubt be disappointed here. The conclusions have been significantly strengthened relative to what was in the TAR, something that of course should have been expected given the numerous additional studies that have since been done that all point in the same direction. The conclusion that large-scale recent warmth likely exceeds the range seen in past centuries has been extended from the past 1000 years in the TAR, to the past 1300 years in the current report, and the confidence in this conclusion has been upped from “likely” in the TAR to “very likely” in the current report for the past half millennium. This is just one of the many independent lines of evidence now pointing towards a clear anthropogenic influence on climate, but given all of the others, the paleoclimate reconstructions are now even less the central pillar of evidence for the human influence on climate than they have been incorrectly portrayed to be.

The uncertainties in the science mainly involve the precise nature of the changes to be expected, particularly with respect to sea level rise, El Niño changes and regional hydrological change – drought frequency and snow pack melt, mid-latitude storms, and of course, hurricanes. It can be fun parsing the discussions on these topics (and we expect there will be substantial press comment on them), but that shouldn’t distract from the main and far more solid conclusions above.

The process of finalising the SPM (which is well described here and here) is something that can seem a little odd. Government representatives from all participating nations take the draft summary (as written by the lead authors of the individual chapters) and discuss whether the text truly reflects the underlying science in the main report. The key here is to note that what the lead authors originally came up with is not necessarily the clearest or least ambiguous language, and so the governments (for whom the report is being written) are perfectly entitled to insist that the language be modified so that the conclusions are correctly understood by them and the scientists. It is also key to note that the scientists have to be happy that the final language that is agreed conforms with the underlying science in the technical chapters. The advantage of this process is that everyone involved is absolutely clear what is meant by each sentence. Recall after the National Academies report on surface temperature reconstructions there was much discussion about the definition of ‘plausible’. That kind of thing shouldn’t happen with AR4.

The SPM process also serves a very useful political purpose. Specifically, it allows the governments involved to feel as though they ‘own’ part of the report. This makes it very difficult to later turn around and dismiss it on the basis that it was all written by someone else. This gives the governments a vested interest in making this report as good as it can be (given the uncertainties). There are in fact plenty of safeguards (not least the scientists present) to ensure that the report is not slanted in any one preferred direction. However, the downside is that it can mistakenly appear as if the whole summary is simply up for negotiation. That would be a false conclusion – the negotiations, such as they are, are in fact heavily constrained by the underlying science.

Finally, a few people have asked why the SPM is being released now while the main report is not due to be published for a couple of months. There are a number of reasons – firstly, the Paris meeting has been such a public affair that holding back the SPM until the main report is ready is probably pointless. For the main report itself, it had not yet been proof-read, and there has not yet been enough time to include observational data up until the end of 2006. One final point is that improvements in the clarity of the language from the SPM should be propagated back to the individual chapters in order to remove any superficial ambiguity. The science content will not change.

Had it been up to us, we’d have tried to get everything together so that they could be released at the same time, but maybe that would have been impossible. We note that Arctic Climate Impact Assessment in 2004 also had a similar procedure – which lead to some confusion initially since statements in the summary were not referenced.

How good have previous IPCC reports been at projecting the future? Actually, over the last 16 years (since the first report in 1990), they’ve been remarkably good for CO2 changes, temperature changes but actually underpredicted sea level changes.

When it comes to specific discussions, the two that are going to be mostly in the news are the projections of sea level rise and hurricanes. These issues contain a number of “known unknowns” – things that we know we don’t know. For sea level rise the unknown is how large an effect dynamic shifts in the ice sheets will be. These dynamic changes have already been observed, but are outside the range of what the ice sheet models can deal with (see this previous discussion). That means that their contribution to sea level rise is rather uncertain, but with the uncertainty all on the side of making things worse (see this recent paper for an assessment (Rahmstorf , Science 2007)). The language in the SPM acknowledges that stating

“Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude.”

Note that some media have been comparing apples with pears here: they claimed IPCC has reduced its upper sea level limit from 88 to 59 cm, but the former number from the TAR did include this ice dynamics uncertainty, while the latter from the AR4 does not, precisely because this issue is now considered more uncertain and possibly more serious than before.

On the hurricane/tropical strorm issue, the language is quite nuanced, as one might expect from a consensus document. The link between SST and tropical storm intensity is clearly acknowledged, but so is the gap between model projections and analyses of cyclone observations. “The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period.”

We will address some of these issues and how well we think they did in specific posts over the next few weeks. There’s a lot of stuff here, and even we need time to digest it!

364 Responses to “The IPCC Fourth Assessment SPM”

  1. 51
    Lynn Vincentnathan says:

    #15, thanks, Spencer, for that clarification. I had thought that 1.5-4 degree C range must have been the climate sensitivity range for 2X CO2, because 4 degrees didn’t seem like the worse-case human emissions scenario (at highest sensitivity). And I believe TAR had the upper figure (of worse case scenario) at 5.8 degrees C. So the AR4 figure would be an increase — am I right? But the media have been jumping around these past few months saying AR4 indicates GW will not be so bad, bec they’ve ratcheted down the warming figures.

    #16, Jake, I’m also concerned with natural GHG emissions increasing due to the warming that the human emissions have caused. I do hope AR4 deals with that, even though such positive feedbacks entail a lot of uncertainty.

    So my question then would be, is 6.4 degrees C the upper end only for the worst case of human emissions (at the highest sensitivity), and thus leaves out the positive feedbacks (nature emitting due to the warming, lower albedo from melting ice)? I mean, is there a possibility of even a higher temp when both human emissions and positive feedbacks are considered.

    From what I understand, positive feedbacks (e.g., from melting permafrost & clathrates, & reduced albedo) are not included in the models.

    #17, I do think a 3 degree increase would be pretty disasterous, esp for the poor peoples of the world (& it would make the rich a lot poorer); it’s sort of like the reichter scale – the change from a 6 to a 7 involves a lot more danger & harm than from a 5 to a 6, so a rise from 2 to 3 degrees C with GW would probably entail a lot more harms than a 1 to 2 degree increase, with a 5 to 6 degree increase extremely bad. You don’t want to go there. I’m just waiting to get Mark Lynas’s SIX DEGREES when it comes out in March; in lay language he takes us through each degree increase — 1, 2, 3, 4, 5, 6 degrees — and what each degree increase would mean re effects and harms.

  2. 52
    Oldfart says:

    Just today the opposition ( is claiming that language such as “One final point is that improvements in the clarity of the language from the SPM should be propagated back to the individual chapters in order to remove any superficial ambiguity. The science content will not change.” is simple proof that making the science fit the summary is what is being done. The idea that a negotiated political “summary” should propagate it’s language back to the detailed science is very suspicious to many people for whom global warming as a result of human activity is NOT a clear fact.

  3. 53
    Ark says:

    #43: Sean, I’m pretty sure that it’s mm/year in both Greenland and Antarctic ice sheets numbers 1961-2003 (like in 1993-2003 numbers). So in metres/century: 0.042+0.050+0.005+0.014=0.111, or approx 0.11.

  4. 54
    Karan says:

    This is extremely shameless. Steven Milloy at has released the draft of the working group 1. How desperate will these political puppets get?

  5. 55
    Ells says:

    Re #15: Maybe just a typo but the SPM defines “very likely” as 90% to 95% certain, “Extremely likely” covers 95% to 99% certain. Very glad to to see the precise definitions of terms that still carry an effective qualitative message.

  6. 56
    Hans Erren says:

    re 19:

    Will Al Gore adapt his sea level projection for The Netherlands?

  7. 57
    pete best says:

    I personally believe that the biggest issue related appears to be the rate of CO2 increase and hence the time that it takes for 2 C of warming to take place. Currently annual emissions increases are 2 ppmv but recent years have seen 2.6 and 2.5 ppmv increases, if that accelerates to 3 ppmv somehow then we could be out of time as 100 ppmv increase to 480 ppmv which would take 50 years at 2 ppmv will only take 33 years at 3ppmv.

    i wonder what the latest 2006 annual increase rates are and whether this is set to increase?

  8. 58
    Sean Davis says:

    I just put up a new post summarizing what (I noticed) has changed in the IPCC from TAR to AR4.
    IPCC SPM- So What’s New?


  9. 59
    Walt Bennett says:

    (If my comment is not suitable for posting, please email me and explain why, thank you.)

    I had asked in the previous blog post (comment was not posted):

    Do we have some sort of numerical representation for the greenhouse effect? In other words, a measurement of total solar energy which reaches the surface, and what percent is direct sunlight versus what percent is the greenhouse effect. Do we have such a number, and have we tracked changes in it (and for how long?

    Thank you.

  10. 60
    SecularAnimist says:

    Off topic, but …

    The American Solar Energy Society today released a 200 page report, “Tackling Climate Change in the US: Potential U.S. Carbon Emissions Reductions from Renewable Energy and Energy Efficiency by 2030” which outlines how the USA can reduce its carbon emissions by 60 to 80 percent by 2030 with improvements in efficiency and deployment of existing clean, renewable energy technologies.

    The 60 to 80 percent reduction is in line with what is needed to keep CO2 concentrations below 450 to 500 ppm, which is what most scientists believe is necessary to prevent the worst effects of global warming.

    Fifty-seven percent of the carbon reductions are from energy efficiency improvements, and forty-three percent are from renewables. No expansion of nuclear power is included in the proposal.

    I know that many frequent contributors to these comment pages are very interested in solutions to the problem of reducing US carbon emissions, and will find this report useful.

  11. 61
    Ajit Singh says:

    Dr Rajendra Pachauri, IPCC chairman and DG, The Energy and Resources Institute & Chair IPCC: “A number of scientists say Siachen should be made a protected area, a heritage site of sorts, and that there should be no army presence on either side. For purely ecological reasons, this *might* be a good idea. But I *don’t* see why there would be melting as a result of military presence and activity.” The *s show a vagueness unworthy of an environment leader who ought to ask for withdrawal of all troops immediately! Click to see the view of chairman IPCC
    So, we should not expect a lot from IPCC, currently head by Dr Rajendra Pachauri, as his biased, unprofessional remarked already appeared in news paper and enough to say that it would be another media hype and noting else.

  12. 62
    SecularAnimist says:

    Walt Bennett wrote: “Do we have some sort of numerical representation for the greenhouse effect? In other words, a measurement of total solar energy which reaches the surface, and what percent is direct sunlight versus what percent is the greenhouse effect. Do we have such a number, and have we tracked changes in it (and for how long?”

    Yes, NOAA tracks that, and reports on it every year in the Annual Greenhouse Gas Index, using 1990 as the baseline.

    NOAA’s May 2006 report, for 2005, found that the total “greenhouse effect” had increased by 21 percent since 1990.

  13. 63

    In the SPM-0 table, in the 1993-2003 column, not only do the central values not add up, but the errors don’t compute either. If the Antarctic uncertainty was 0.35m/century, that would dominate the uncertainty in the sum which would therefore have to be much larger than 0.07m/century.

    Pretty surprising to see elementary errors like this in such a profoundly important document. Too many late nights? It’s still broken as of right now.

    [Response: It’s a simple unit conversion error, some values (including their error bars) are accidentally in mm/yr, not in m/century, hence they are a factor of 10 too large. -stefan]

  14. 64
    SecularAnimist says:

    More evidence of global warming:

    PUNXSUTAWNEY, Pennsylvania (AP) — A new pair of hands pulled Punxsutawney Phil from his stump this year, so it was only fitting that the groundhog offered a new prediction.

    Phil did not see his shadow on Friday, which, according to German folklore, means folks can expect an early spring instead of six more weeks of winter.

  15. 65
    Marcus says:

    #52: Walt: Figure SPM-2 in the new summary shows the (direct) anthropogenic contribution to the greenhouse effect of 1.6 W/m2 (0.6 to 2.4 W/m2 bounds). One presumes there would be a further indirect effect of increased water vapor forcing and albedo change from melting ice that aren’t quantified here (though they do quantify albedo change from black carbon in snow and land use).

    This compares to: average sunlight: about 240 W/m2 (that’s 1368 W/m2 divided by 4 for surface area of a sphere vs. a circle times 0.7 for earth’s albedo) (said insolation keeps us at 255 K), plus natural greenhouse of about 150 W/m2 (bringing us to 288 K). With about 0.1 W/m2 solar increase since 1750.

    They don’t report the increased forcing from the 6 SRES scenarios, but I would guess (looking at temperature changes) that the direct forcing increases range from 3.5 W/m2 to maybe 12 W/m2 above preindustrial.

    So perhaps 8 W/m2 direct anthropogenic forcing, with additional forcing from water vapor/cloud and ice albedo changes of perhaps 3 times the direct effect (a rough estimate based on a climate sensitivity of 3), means 32 W/m2 human caused forcing, which would be equal to an increase of 20% in natural forcing or a 13% increase in the Sun, or an 8% increase in all forcing. That’s pretty big (enough for 6 degrees C above preindustrial at equilibrium). Obviously, changes in climate sensitivity estimates or emissions forecast can increase or decrease that number by a lot.

    (RC moderators, please correct me if I’ve made any calculation errors)

  16. 66
    Dan says:

    re:53. “How desperate will these political puppets get?”

    Money talks a lot for the likes of them.

  17. 67
    Pat Neuman says:

    Re 49 … a lot of extra precpitation looking for somewhere to go. Where will it all end up?

    A lot of the extra precipitation will end up falling as rain in the higher latitude regions.

    The increase in humidity will increase latent heat.

    The significance of latent heat for snowmelt has been described by Dunne and Leopold (1978):

    �If water from moist air condenses on a snowpack, 590 calories of heat are released by each gram of condensate. This is enough energy to melt approximately 7.5 gm of ice, which when added to the condensate yields a total of 8.5 gm of potential runoff�.

  18. 68
    SolarNTrains says:

    Re: 59 – Excellent URL with good, pragmatic information. IMHO I don’t think it is realistic to assume 60 to 80% alt energy is achievable without nuclear. While I can’t speak for the other sources, I know from work experience that solar has major challenges, and even the authors of the article don’t describe potential outcomes as “likely”. But any amount would be an excellent start.

    BTW, secularanimist, go lite on us conservatives(ala 34 and other comments on RC) that don’t always agree with you.

  19. 69
    RepublicanGuy says:

    “The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive.” Greenhouse Gas via Wikipedia.

    Well what is it for CO2? 9% or 26%? That looks to me a pretty big margin of error. A multitude of 3 margin of error, ouch.


    99 ppm added CO2 from pre-industrial to 2007.

    So how much more thermal energy is added to earth per square kilometer, with 99 more ppm, and how much would that theoretically raise the temperature of the earth in total? Theoretically speaking. No need to adjust for clouds, water vapor, etc, just how much more thermal energy is added.

    [Response: Funny guy. You should probably investigate where that information came from – I’m sure it’s reputable and they’ll probably explain what the range means…. (hint) – gavin]

  20. 70
    Marcus says:

    RepublicanGuy: 9% to 26% is not _margin of error_ it is a fundamental difficulty in assigning a number. The number you get by taking a vacuum and adding 270 ppm of CO2 is a lot different than the number you get by taking the preindustrial atmosphere and subtracting 270 ppm CO2 (I would guess that 26% is the first approach and 9 % the second). This occurs because the various gases have overlapping spectra.

    The SPM states that the increase in CO2 leads to a 1.66 W/m2 increase in forcing. I know that doubled CO2 (4 W/m2) has about a 0.8 degree C direct contribution to temperature (along with .7 to 3.7 degrees feedback), so 1.66 W/2 would be about 0.3 degree C, with 0.3 to 1.4 degree additional feedback expected. We’ve seen 0.8 degrees of warming, and expect 0.6 degrees more, which falls within that range.

    Does that answer your question?

  21. 71
    Joseph Siry says:

    The current scientific consensus is (found in comparing AR-4 to TAR) based on far greater certainty that global warming is due to human actions, that the sharp rise in heat trapping gases since the 1950s is not a natural cycle, and this condition will not soon go away. The evidence is clear that actions must be taken soon because the rates at which carbon dioxide, methane and nitric oxide are increasing are unprecedented. Present levels of carbon dioxide in the atmosphere have not been detected on earth for over 600,000 years.

    Because of these facts, ocean chemistry and temperature are undergoing an accelerating change. Levels of rainfall are increasing in the polar latitudes. Heavy precipitation events occur more frequently and rapid runoff of rainwater increases the rate of erosion. In the sub-tropics there is less rainfall predicted. Given such trends, our inability to manage water, protect low-lying coastal areas and reduce the loss of topsoil should promote widespread caution.

    These facts make it clear that actions needed to cap and then reduce the rate of heat trapping gas emissions will have greater impact if taken sooner, than if we stall in efforts to be more energy efficient. Because warmer oceans and land areas will persist for decades, if not centuries, institutional changes must be encouraged now to assist the most vulnerable and curb inherent inefficiencies in power consumption and transportation.

    As the U.K. government campaign is fond of saying tomorrow’s climate depends on today’s actions.

  22. 72
    Dave says:

    Does anyone have any insight as to how Richard Lindzen developed views that are so far out of the scientific mainstream? Is he just kissing the hand that feeds him or are his views of climate change part of a monetary (Grover Norquist-like) or religious (rapture – obsessed) conservative ideology?

    [Response: Somebody else can figure out the psychology of Lindzen’s denialism, but it’s not really important. What’s important is whether he has any arguments that bear scrutiny. The last actual argument he published was the IRIS cloud feedback mechanism, a good many years back, which did not stand up to scrutiny. All of his earlier arguments (cumulus drying, super-lapse-rate feedback) were demonstrably wrong. So far as I can tell he has stopped making scientific arguments. That’s what counts. He’s playing his MIT professorship for all that it’s worth, but that’s all he’s got going for him right now. –raypierre]

  23. 73
    Roger Smith says:

    I think Lindzen’s always been a maverick and because of that has asked questions about what others just assumed to be true. This approach may be wrong 99% of the time, but it’s the 1% that wins scientific awards. Hopefully he’ll stop wallowing in the 99% soon and move on.

  24. 74
    Dave Cohen says:

    I’ve got to ask — what is the deal? I posted (#8), and my colleague (#64, and others) posted on how the AR4 math is wrong, showing that global sea level rise is not well accounted for in the publicly released document.

    I am forced to ask — considering some “Freudian Slip” situation — how the release of this long-awaited 2007 document could both 1) do the math wrong and 2) discount current sea-level rise trends from the big ice sheets in Greenland and W. Antarctica.

    I eagerly await some reponse — or “rationalization” — as to how this can be explained.

  25. 75
    Lee Morrison says:

    #71 Sorry that you disliked my post sufficiently to zap it, Dan. I’m retired, but I was a successful and (I think) respected scientist for almost 40 years. I do know a little bit about what constitutes science. Computers have made our work immeasurably easier, but they haven’t yet replaced the ability of human beings to think logically and collect data objectively. Clever computer programming is a valuable skill, but it isn’t science.

  26. 76
    Scott L. Montgomery says:

    #61. Thanks very much for the link to this report! It does indeed talk about renewables and energy efficiency, as carbon mitigation measures for the U.S. and proposes we can reduce carbon emissions by 60-80 percent this way. Unfortunately, the report is a theoretical treatise–its authors were asked what they thought could be potentially accomplished, given resource assessments and technological capabilities. No consideration is given to many real world aspects, such as the politics of land use and ownership, full costs of deployment and existing power plant replacement, grid adjustments, ecological problems (due to the very large land requirements for large scale solar and wind), and much much more. These sorts of pie in the sky studies have plagued renewables from the beginning and torture us with the prospect of revolutionary change, but they do a disservice to an industry that is now in the throws of real practical expansion, due to both high energy prices and climate change worries. But these forces have their limits, as do renewables themselves. As presently conceived, renewable sources will not run the world, or even a large portion of it. They are currently less than 1 percent of global energy use, and though very important for a range of countries, from Iceland to India, they are far from equal to the task of turning over the 12 trillion dollar fossil fuel system. The future lies with energy diversity, an expanding and increasingly flexible portfolio of sources. Technology won’t solve it all, by any means, but it will help enormously. For a good discussion of energy issues related to climate change, see John Holdrens article The Energy Innovation Imperative, at
    The future lies with a diversity of sources

  27. 77
    Robin Henkys says:

    Doing some late night reading on this subject as a result of the vast media coverage of the IPCC report. I personally haven’t really had any doubts about the human impact on global warming, but I am merely a student of Computing and have no deep scientific understanding of the subject (one tries though).
    This is just a thank you to the authors for this blog.

  28. 78
    Stormy says:

    To the editors:

    According to The Guardian, the AEI (American Enterprise Institute) thinktank is offering $10,000 to anyone who will cast doubt on the report, scientists and economists included.

    I suggest you get a copy of that letter and publish it here, together with who funds the AEI.

  29. 79

    #37 Pat, Rebound has been continuous process since the last ice age, quite severe in the Arctic, where you find very old Bow head whale skeletons, ancient half burried walruss skeletal heads 160 meters above sea level! Present rate around where I live is about 2 cm a year, where raised beach ridges are a common shoreline sight..
    What recent GW does to rebound is a very good question…

  30. 80
    Andrew Dessler says:

    I blogged on the new IPCC report and my take here. Take a look and let me know what you think.

    [Response: Hi, Andrew. I think this is a very nice summary of the highlights of the report. I’ll leave it to Mike Mann to comment on your take on whether the nuances of the NAS statement on climate of the past millennium is significantly different from what the SPM says. It all comes down to details of how one estimates the uncertainty in reconstructions of medieval warmth. Nobody can say that the Medieval was definitely warmer (hemispherically) than the present, but some might say that the error bars are large enough that one cannot rule out the possibility. In some sense you are right that there were no real scientific breakthroughs reported in this round. The improvements were incremental, and the big news was in how fast the Earth’s climate is changing. The SAR, in contrast, introduced a breakthrough in the aerosol connection to interrupted warming, whereas the TAR had some breakthroughs in coupled ocean-atmosphere modelling. The timing of AR4 just missed the next big breakthrough — which will be in improved and coupled modelling of glacier dynamics, including fracture mechanics, ice shelves and all that stuff. I think one mustn’t discount a breakthrough of a technological sort in AR4 though: The number of model runs exploring more of scenario and parameter space is vastly increased, and more importantly, it is available in a coherent archive to the full research community for the first time. The amount of good science that will be done with this archive in the next several years is likely to have a significant impact on our understanding of climate. –raypierre]

    [Response: One clarification on the point made by Ray P above. Actually, the IPCC statement is stronger than what Ray suggests. The careful choice of wording by the IPCC on this indicates that they did think we can rule out the possibility that Medieval large-scale warmth was comparable to the present at a moderately (likely=67%) high level of confidence, and that is of course taking into account the fact that there are uncertainties. –mike]

    [Response: As we note in the piece above, the NRC did endorse the key conclusions of IPCC (2001) with regard to millennial reconstructions, hence news reports in e.g. Nature such as “Academy Affirms Hockey-Stick Graph”. Nonetheless, the NRC report was a rush job, was forced to ignore key papers in the pipeline, and had limited representation of experts in paleoclimatology (perhaps seeking breadth but sacrificing depth in this key area in their selection of panel members). By contrast, the IPCC was a long, careful, deliberate process, based on several years of thorough assessment of the literature, the IPCC paleoclimate chapter was written by leading experts in the field of paleoclimatology, and input was solicited from essentially every leading expert in the field. It should be unsurprising that they came to a somewhat different (and in my view, more accurate) bottom line. I hope that answers the question for you Andrew? –mike]

  31. 81
    Colorado Bob says:

    Neal Boortz is on the attack :
    25 Reasons to blah, blah, blah ……

  32. 82
    Peter says:

    What are your thoughts regarding Christopher Monckton’s analysis of the 4AR?

  33. 83
    Alvia Gaskill says:

    Bodman et al. Embrace IPCC Report Sort Of

    After the IPCC Committee delivered its report, officials from the U.S. government gave their take on it. Energy Secretary Sam Bodman, NOAA Administrator Conrad Lautenbacher and EPA Administrator Stephen Johnson each made remarks and answered questions. (shown on CSPAN2).

    They said that they and the Bush Administration embraced the IPCC report and that without the funding for scientific research sought for and received by the president starting in 2002, the IPCC would not have been able to deliver its final product. In other words, U.S. government funded research was responsible for much of the scientific content in the report.

    Bodman cited 7 DOE supercomputers funded by the Bush administration as key elements in generating this scientific work.

    All three repeatedly referred to the $29 billion spent by the Bush administration over the last 6 years on climate change research and greenhouse gas mitigation.

    So where did this figure of $29 billion originate? Only a few years ago the White House was claiming that it spent $2 billion a year on climate research and then $3 billion and now the $29 billion figure so frequently quoted by administration spokesmen today.

    That would work out to about $5 billion per year and indeed seems be consistent with the numbers in a WH press release from last year. See below.

    From 2001 To The End Of 2006, The Federal Government Will Have Devoted Over $29 Billion To Climate Programs, More Than Any Other Nation. The President�s 2007 Budget proposes $6.5 billion for climate change activities.

    However, others, including the National Environmental Trust, the GAO and AAAS haven’t had much success in verifying these numbers.

    Some people, like James Hansen, for example, have openly complained about budget cuts in monitoring programs. What then is the true story of the $29 billion? The link below to the USAID provides a breakdown by agency and area.

    The money spent in 2006 was about as follows:

    Climate Science $1.9 billion of which $1.3 was from NASA.

    Climate Change Technology Program $2.8 billion of which $2.5 was from DOE

    Tax Credits $1 billion

    The proposed increase in 2007 is mostly due to a big increase in the tax credits, while the science funding drops off.

    EPA and NOAA’s funding are less than $200 million each, although Lautenbacher and Johnson did not seem concerned about this.

    Of the DOE’s budget, around $1.2 billion is in the category Energy Efficiency and Renewable Energy. Somewhere between $500 million and $1 billion is associated with carbon capture and sequestration.

    The biggest complaint about these numbers is that the Bush administration has continually broadened the definition of what constitutes climate change research and mitigation, thus making it appear that the funding for this area is skyrocketing when in fact it is actually going down in some categories.

    Bodman also said that the U.S. would not adopt a GHG cap unilaterally, out of concern this would drive jobs overseas to countries with no caps and lax air pollution standards, thereby making the overall problem worse.

    A reporter then pointed out that Germany has had caps in place for several years and has experienced job growth. Bodman said he was sure someone would perform an economic analysis that would clarify this.

    Another reporter asked that since California now has its own version of a GHG cap in place, wouldn’t it be expected to lose jobs? Bodman said he thought this would be the outcome.

    One hopeful note. Bodman said that U.S. scientists would be made available to talk to the media about the IPCC report. Of course, he didn’t say which scientists and under what circumstances. After all, buried somewhere in the $29 billion is a line item titled Salaries.

  34. 84
    BarbieDoll Moment says:

    (Re: 2

    Could tectonic rebound from ice loss on Greenland and Antarctic result in additional significant increases in sea level? )

    However there are not the observed temperature changes in the Antartic, so isn’t that
    putting the cart before the horse? ….

    “Climate Change 2007: The Physical Science Basis Summary for Policymakers
    Working Group I”
    IPCC WGI Fourth Assessment Report, (Feb 2007) report

    …..”Some aspects of climate have not been observed to change. {3.2, 3.8, 4.4, 5.3}

    “â?¢ Antarctic sea ice extent continues to show inter-annual variability and localized changes but no statistically
    significant average trends, consistent with the lack of warming reflected in atmospheric temperatures
    averaged across the region. {3.2, 4.4} “….

    …”It is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica (see Figure SPM-4).”….

    …”â?¢ Global average sea level in the last interglacial period (about 125,000 years ago) was likely 4 to 6 m higher than during the 20th century, mainly due to the retreat of polar ice. Ice core data indicate that average polar temperatures at that time were 3 to 5°C higher than present, because of differences in the Earthâ??s orbit. The Greenland ice sheet and other Arctic ice fields likely contributed no more than 4 m of the observed sea level
    rise. There may also have been a contribution from Antarctica. {6.4}”…

    …”Current global model studies project that the Antarctic ice sheet will remain too cold for widespread surface melting and is expected to gain in mass due to increased snowfall. However, net loss of ice mass could occur if dynamical ice discharge dominates the ice sheet mass balance. {10.7}”…

    and one could refer to any of the following as well for other science on the matter

    ECORD: IODP Expedition 310-Tahiti Sea Level

    “So far, the only sea-level record that encompasses the whole deglaciation is based on offshore drilling of Barbados coral reefs which overlie an active subduction zone and was located close to the former ice sheets during the Last Deglaciation. Vertical tectonic movements in such areas may be large and are often discontinuous, implying that apparent sea level records may be biased by variations in the rates of uplift. Hence, there is a clear need to study sea level changes in tectonically stable regions or in areas where vertical movements are slow and/or regular. Furthermore, the eustatic function is best estimated from sea level data collected far from the former ice margins where the the influence of glacio-isostatic rebound is minimized”…

    Volcanic and tectonic processes coinciding with glaciation and crustal rebound: an early Holocene rhyolitic eruption in the Dyngjufjöll volcanic centre and the formation of the Askja caldera, north Iceland
    Bulletin of Volcanology 64 (3-4), 192 (2002)

    “A pronounced volcanic production maximum on the rift zones through Iceland coincided with rapid crustal rebound during and after glacier melting at the Pleistocene/Holocene boundary. At peak glaciation, ice thickness over central Iceland may have reached 1,500-2,000 m, causing 400-500-m depression of the crust. Rapid climatic improvement caused glacier melting and removal of the ice load within about 1,000 years. Low mantle viscosity resulted in rapid crustal rebound which was completed in about 1,000 years, with an average rate of uplift on the order of nearly half a metre per year over central Iceland.”..”A model is proposed involving uplift of tectonically well-defined crustal blocks to the north and west of the Askja caldera, combined with downsagging caused by voluminous outpouring of basaltic lava. The southern and eastern borders of the caldera are remnants of a subsidence following the 10-ka Plinian eruption, partly reactivated by the 1875 A.D. Plinian eruption. The model provides a satisfactory explanation for the enigmatic Ã?skjuop pass, and it is in agreement with a gravity survey of the Dyngjufjöll centre. The uplift coincided with rapid crustal rebound which was amplified by crustal deformation (doming) of the volcanic centre caused by high magmatic pressure in the plumbing system of the volcano. This is supported by emission of very large lava flows produced in the first millennia of the Holocene. ”

    Decontaminating tide gauge records for the influence of glacial isostatic adjustment: The potential impact of 3-D Earth structure
    Geophysical Research Letters 33 (24), 24318 (30 Dec 2006)

    Observation of glacial isostatic adjustment in â??stableâ?? North America with GPS
    G F Sella et al.
    Geophys. Res. Lett 34 (L02306), (26 Jan 2007)

    RE: (51. …”Yet the report forecasts droughts and reductions in rainfall most places.”)

    “Climate Change 2007: The Physical Science Basis Summary for Policymakers
    Working Group I”
    IPCC WGI Fourth Assessment Report, (Feb 2007)

    ..”â?¢ The frequency of heavy precipitation events has increased over most land areas, consistent with warming
    and observed increases of atmospheric water vapour. {3.8, 3.9}”…

    RE: (46. Where is the discussion of natural variability in all this?”)

    “Climate Change 2007: The Physical Science Basis Summary for Policymakers
    Working Group I”
    IPCC WGI Fourth Assessment Report, (Feb 2007)

    ….”â?¢ Difficulties remain in reliably simulating and attributing observed temperature changes at smaller scales.
    On these scales, natural climate variability is relatively larger making it harder to distinguish changes
    expected due to external forcings. Uncertainties in local forcings and feedbacks also make it difficult to
    estimate the contribution of greenhouse gas increases to observed small-scale temperature changes. {8.3,

    and the footnote

    “1 Climate change in IPCC usage refers to any change in climate over time, whether due to natural variability or as a result of human activity. This usage differs
    from that in the Framework Convention on Climate Change, where climate change refers to a change of climate that is attributed directly or indirectly to human
    activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods.”

  35. 85
    naught101 says:

    why to the IPCC use the “Virtually certain”, “Extremely likely”, “Very likely”, “Likely”, “More likely than not”, “Unlikely”, “Very unlikely” and “Extremely unlikely” qualifiers? it makes it difficult to read. it would make much more sense to just use a range of likelyhoods – “it is 90-99% likely that x will happen.” much easier to read, and also less restrictive, as figures such as 85-95% could be used, or specific figures with uncertainties: 90% ±4%. this would make the entire report that little bit more accurate, and MUCH, MUCH easier to read.

    the same could go for the “High Confidence” etc.

    #26: absolutely classic. I haven’t heard a comment so backwards for years! I’m gonna have fun with comments like these in the next few weeks.

  36. 86
    Mike Hart says:

    A quick question for the RC crew or any other scientist re Polar cap changes. ‘Are there any studies about the possibility of a orbital shift for the planet with the change in mass from ice to water?”. I note a recent private published book by Prof Lance Endersby who suggests that such orbital shifts may have been induced by glacial change in the past. A suddent orbital shift would be more than catastrophic it would suggest a major extinction event. Any responses would be appreciated

  37. 87
    BarbieDoll Moment says:

    I gather that this prelim policy laymen’s type of summary report is not the actual technical bling-bling we should expect of the IPCC AR4 coupled climate models, because according to LLNL, such will be released in chapter 8?

    As far as a sense of homogeneity across the models, what actual number of modeling input factors (ex: Co2, solar, clouds) would encompass the said physical sciences of “atmosphere, land surface, ocean and sea ice” that were submitted specifically to the IPCC AR4 for consideration? Ten ? More, less?

    Additionally, will the release of chapter eight further quantify the uncertainties, bias, differences and so forth in relation to the various model versions simulations, within their range and scope, in consideration to their ability to reproduce, replicate, and or be in some form of a consensus data output agreement?

    Or will we have diverging model outputs that persist in diverging projected climatic opinions or lack of certaintities? Excusing of course the nonlinearity factors of the natural climate systems which will always, I assume, interject its whims; especially at the shorter intervals versus longer climate patterns; further compounding the matter for modelers.

    About IPCC Model Output
    …”the PCMDI is archiving coupled ocean-atmosphere general circulation model output to support the Working Group 1 component of the IPCC’s 4th Assessment Report. The data archived by the PCMDI from each participating coupled ocean-atmosphere model is a subset of that model’s output. Working Group 1 of the IPCC focuses on the physical climate system — atmosphere, land surface, ocean and sea ice — “…

    Important Information for Analysts and Authors
    ..” The overall purpose of Chapter 8 of the AR4 is to assess the ability of the global climate models to make projections of future climate change.”…

    IPCC Climate Model Documentation, References, and Links

  38. 88
    BarbieDoll Moment says:

    (RE:2 ..”Greenland glaciers finally melt (either slowly or in a big whoosh) tectonic rebound will probably increase the frequency and magnitude of earthquakes around the world.”…)

    If the thought intrigues you, there are research papers out there
    discussing the topic and or similar trains of thoughts.


    “In a new study, NASA and United States Geological Survey
    (USGS) scientists found that retreating glaciers in southern
    Alaska may be opening the way for future earthquakes.”…”Even though shrinking glaciers make it easier for earthquakes
    to occur, the forcing together of tectonic plates is the main
    reason behind major earthquakes.”…

    “Earthquakes in Greenland: Are They Related to Postglacial Rebound?”
    Chung, W. AGU 2000 Spring Meeting“S32A”

    “An intriguing observation in Greenland is a clear spatial correlation between seismicity and deglaciated areas along passive continental margins, a piece of evidence of earthquake triggering due to postglacial rebound. Another piece of evidence of induced seismicity due to deglaciation is from earthquake source mechanisms.”…”These and two prior events support the theory that the shallow part of the lithosphere beneath the deglaciated margins is under horizontal extension. The observed stress field can be explained as flexural stresses due to removal of ice loads and surface loads by glacial erosion. These local extensional stresses are further enhanced by the spreading stress of continental crust and reactivate preexisting faults. Earthquake characteristics observed from Greenland may be typical of those along the deglaciated passive margins elsewhere. ”

    Lateral viscosity variations beneath Antarctica and their implications on regional rebound motions and seismotectonics
    Wu, P. P.; Kaufmann, G.; Ivins, E. R. American Geophysical Union, Spring Meeting 2004, abstract #G33A-13 (05/2004)

    …”Fault stability is predicted over much of Antarctica today, indicating that the seismically quite state is probably due to the presence of the thick ice. At the site of the 1998 Balleny Island Earthquake (Mw=8.1), the induced fracture stresses are relatively small by comparison, and interestingly become more prone to stress failure when a three-dimensional earth model is assumed.”

    Glacial isostatic stress shadowing by the Antarctic ice sheet
    Ivins, Erik R.; James, Thomas S.; Klemann, Volker Journal of Geophysical Research, Volume 108, Issue B12, pp. ETG 4-1, CiteID 2560, DOI 10.1029/2002JB002182 (12/2003)

    “Numerous examples of fault slip that offset late Quaternary glacial deposits and bedrock polish support the idea that the glacial loading cycle causes earthquakes in the upper crust. A semianalytical scheme is presented for quantifying glacial and postglacial lithospheric fault reactivation using contemporary rock fracture prediction methods”…”A thick lithosphere, of the order of 150-240 km, augments stress shadowing by a late melting (middle-late Holocene) coastal East Antarctic ice complex and could cause present-day earthquakes many hundreds of kilometers seaward of the former Last Glacial Maximum grounding line.”

  39. 89
    Steve Bloom says:

    Re #74: Dave, obviously the arithmetic error in the table is a bit embarrassing, but it’s really just another sign that the just-released document was itself still somewhat a draft. The point is that the substance of the document isn’t affected. I’m sure they’ll fix the problem pronto.

    Regarding your specific concern, I think the SPM made it clear that all that can be done now is to allow for sea level rise from 1) thermal expansion, 2) melt in place and 3) a more or less linear extrapolation of the small amount of dynamical melting that has been observed so far. While it is the expert judgement of many glaciologists that dynamical melting will accelerate very rapidly, there aren’t the needed models or terrain surveys in place as yet to be able to do more than make educated guesses. As a result, all that could really go into the AR4 was the vague statement to the effect that dynamical melting could make things much worse. Really I’m just re-stating what was said toward the end of the post, but hopefully I’ve made things a bit more clear.

  40. 90
    pete best says:

    One other small point, we do not have anywhere near enough fossil fuels reserves to achieve the higher and hence more alarmist scenarios unless we invoke large scale positive feedback loops for large releases of CO2 from natural sources such as the siberian permafrost, or rain forests etc and as RC are always telling us the Science does not tell us that until temps reach 3 C above now. By 2030 Oil and Gas would have peaked and coal cannot scale to take there place so the REALITY of the climate situation is that we are going to get around 1 to a 2 C rise in temps as a maximum.

    So lets not get too alarmist about the doomed world.

    [Response: Would that this were true. There is more than enough coal to go to at least 4xCO2, depending somewhat on how fast you burn it, and if they figure out how to tap into seafloor methane clathrates, it could go even higher. What’s the support for your statement that “coal cannot scale to get there”? –raypierre]

  41. 91
    Pat Neuman says:

    Excerpt from interview transcript posted at Climate Science Watch website regarding sea level issue, BBC World News, February 2, 2007.

    … Interview with Sharon Hays, Associate Director/Deputy Director for Science [OSTP] at the White House Office of Science and Technology Policy, leading the United States delegation, and Rick Piltz, Director, Climate Science Watch.

    BBC interviewer in Paris: �[Sharon Hays] told me what she learned:

    BBC: And the sea level rise is one of the issues that is most contentious through the week. Many people have said, many people are saying that, what you�ve agreed is effectively too conservative, it�s too low, that sea level is rising quicker than what is reflected in this report.

    Hays: Right. What happened with this report is that the model projections we know don�t fully take into account the melting of the ice that we are seeing. And I think that the report dealt with this issue in a very a satisfactory way in that it reported the projections that the models have put out�and I should note that those models now have less certainty than they did in the previous report�but it deals with the fact that this ice is melting at a faster rate than we expected and is not accounted for in the models, by simply stating that. And it states it in the report very clearly and makes it clear that the projections are a baseline, so to speak, that we expect the melting to be greater.

  42. 92
    llewelly says:

    pete best (now #57) said:

    Currently annual emissions increases are 2 ppmv but recent years have seen 2.6 and 2.5 ppmv increases, if that accelerates to 3 ppmv somehow then we could be out of time as 100 ppmv increase to 480 ppmv which would take 50 years at 2 ppmv will only take 33 years at 3ppmv.

    Last 10 years annual mean CO2 rise (ppmv), from NOAA’s ERSL, global monitoring division :

    1997 1.96
    1998 2.90
    1999 1.38
    2000 1.24
    2001 1.84
    2002 2.36
    2003 2.23
    2004 1.65
    2005 2.41
    2006 2.25

    Note the Mauna Loa results at the top of the same page have slightly higher numbers for some years:

    1997 1.98
    1998 2.95
    1999 0.91
    2000 1.75
    2001 1.61
    2002 2.55
    2003 2.31
    2004 1.54
    2005 2.54
    2006 2.34

    But for this purpose, point samples should not be used alone when global averages are available.
    This is not to say that 3 ppmv global annual increases are not possible, but there has not been anything above 2.5 since 1998.

  43. 93
    matt says:

    What is the potential albedo effect relating to increased desertification, has anyone researched the potential of desert albedo to offset global warming, and due to the higher angle of incidence would this have more or less effectthan the melting of the artic per unit area(assuming the desert is near the equator)? Do you think I could convince Lindzen that this is his next big idea?

  44. 94
    Pascal says:

    It seems that CO2 cycle feedback are, in AR4, included.
    It’s said in this report that this feedback explains till +1°C for the high value of the range(for A1F1).
    Were this effect also included in TAR?

  45. 95
    Ray Ladbury says:

    It is interesting to me that so-called skeptics have chosen to attack the climate change issue based on the science, when in reality the source of their opposition is clearly the economic consequences that may result from combatting climate change. My experience is that they often understand economics much better than they understand climate science. I think there is a constructive role in the debate for conservative economic opinion. We certainly will not be able to address climate change if our economy is weakened. Continuing to attack the science at this point is merely a recipe for moving yourself to the margins of the debate.

  46. 96
    bill says:

    Could someone elucidate the section on page 10 under the “projections of future climate changes” heading? I’m looking at the part about “even if all concentrations of ghgs and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1 c per decade would be expected.” Am I right in reading that to mean that if, for example, we’d gone to work hard in 1988 and done everything we needed to do to stop emissions growth by 2000 we’d now be seeing increases in temperature at about half the current rate? I think it’s interesting if that’s the correct reading, because it should give us some sense of the scale of change that real efforts could produce. But I’m not sure I’m reading it correctly (and I have to say that this SPM is not as well-written as the TAR)

    [Response: Thanks for stopping by Bill, its an honor. Your read on this is correct, its the so-called ‘commitment to warming’ rearing its head once again. The mid and deep ocean continue to warm for decades in response to any given perturbation in greenhouse gas concentrations. This makes stabilizing global mean surface temperature a bit like steering a supertanker. This is why many, such as Jim Hansen, have indicated we don’t have much time to act (a decade perhaps) if we are to avoid crossing thresholds that may represent ‘dangerous anthropogenic interference with the climate’. –mike]

  47. 97
    Pat Neuman says:

    Re: We should also be aware of less absorption of atmospheric CO2 by oceans as the waters keep warming and out-gassing of CO2 from some shallower and warmer sea regions.

  48. 98
    Phil says: are so upset at what they see as political interference in the IPCC scientists’ report that they have leaked the full drafts of the fourth assessment:

  49. 99
    Lynn Vincentnathan says:

    RE #45 & natural climate variability. I see it like this, the ocean has waves, up & down, and ebb & flood tides. But then something outside this system happens, an ocean earthquake, and we get a tsunami.

    We all felt very bad re the tsunami victims, that they didn’t even know what was coming though the signs (to the knowledgeable) were there. Let’s become wise, listen to the knowledgeable & act now to avoid disaster.

    As Sen. McCain recently said, the debate is over; it’s time to act. Something I was saying 17 years ago, before science reached scientific certainty on this. Would a person take poison because it was only 94% likely to kill, and not 95% certain? Would a doctor tell a patient they won’t remove the lump because it’s only 94% certain to be cancerous, so come back in a year & see if it reaches 95% certainty?

  50. 100
    tamino says:

    Re: #95

    I think there is a constructive role in the debate for conservative economic opinion.

    I agree. But I don’t think the attacks on the science are coming from those who are truly economic conservatives.

    There’s a vast difference between economic conservatives and robber-barons. The present U.S. administration serves the latter, while paying lip service to the former. What kind of true economic conservative gives us the biggest federal budget deficits in the history of the world — isn’t paying your bills fundamental to sound economic conservatism? It’s high time we (the voting public) stopped accepting plain old greed as “economic conservatism.”

    Perhaps the best analysis of global warming from an economic standpoint is the Stern report. And the so-called conseratives (actual robber-barons) are about as angry about that, as they are about the IPCC report.