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Filed under: — eric @ 24 November 2009

Nov. 24th, 2009 Copenhagen Diagnosis

The ‘Copenhagen Diagnosis‘, a report by 26 scientists from around the world was released today. The report is intended as an update to the IPCC 2007 Working Group 1 report. Like the IPCC report, everything in the Copenhagen Diagnosis is from the peer-reviewed literature, so there is nothing really new. But the report summarizes and highlights those studies, published since the (2006) close-off date for the IPCC report, that the authors deemed most relevant to the negotiations in Copenhagen (COP15) next month. This report was written for policy-makers, stakeholders, the media and the broader public, and has been sent to each and every one of the COP15 negotiating teams throughout the world.

Among the points summarized in the report are that:

The ice sheets are both losing mass (and hence contributing to sea level rise). This was not certain at the time of the IPCC report.

Arctic sea ice has declined faster than projected by IPCC.

Greenhouse gas concentrations have continued to track the upper bounds of IPCC projections.

Observed global temperature changes remain entirely in accord with IPCC projections, i.e. an anthropogenic warming trend of about 0.2 ºC per decade with superimposed short-term natural variability.

Sea level has risen more than 5 centimeters over the past 15 years, about 80% higher than IPCC projections from 2001.

Perhaps most importantly, the report articulates a much clearer picture of what has to happen if the world wants to keep future warming within the reasonable threshold (2°C) that the European Union and the G8 nations have already agreed to in principle.

The full report is available at Three of us at RealClimate are co-authors so we can’t offer an independent review of the report here. We welcome discussion in the comments section though. But read the report first before commenting, please.

146 Responses to “Copenhagen”

  1. 101
    Jordan L says:

    Great summary of the key points in this most important report. I’m quite nervous, to say the least, about what will result in Copenhagen. I wish there was a way to effectively educate the public the dangers a few degrees in temperature pose to ice sheets, sea levels and many climate processes that are difficult to control and understand such as ocean currents and extreme weather patterns. While this sort of report is necessary, I wonder how effective these scientists are at getting the word out on these disturbing findings. If you interested I further express my own frustrations, specifically at the American government, in a column on my blog: .

  2. 102
    TD says:

    Neophyte Request:

    For some years I have been searching for an ACCESSABLE book that explains AGW. The books I have consulted rely way, way to heavily on argument from authority. “Smart people say this, so you are wise to believe it.” They rarely explain the underlying data and pros/cons of using this data set or that data set. I find the Cophenhagen Diagnosis suffering from the same problem (at least for a neophyte like me)

    If I could order a book its outline would be like:
    1.Remembering your high-school earth science – explaining the radiative balance and heat distribution throughout the world. The roles of clouds, currents, etc. etc.
    2.CO2’s role in that balance and its significance/magnitude against other factors. (The report today addresses this when it compares C02 vs soloar!!!!)
    3.Measuring temperature from Ancient times (the past 1000’s of years.) The insight and problems of using proxy data. It would list the proxies. It would list the pro’s and con’s of each proxy.
    4.Measuring temperature in modern times. Weather stations, satellite, others. Getting this temperature at the Earth’s surface, significant altitudes and land vs sea.
    5.Explanation of the various forecasts and the significant factors that explain their difference.

    No AGW book that I have ever seen does this. Instead, they throw up a bunch of graphs and quote a lot of studies and say “now, we must act.” This is an argument from authority. As such, it is unpersuasive.

    I have had my eye open for such a book but one has never found me, nor I it.

    Books not worth recommending to me:
    1. Al Gore’s various books. Too political, even if it is good science.
    2. M Mann’s Dire Predictions. Just throws up the usual graphs. Does not explain the underlying pro’s and con’s of proxy data, for example
    3. Gavin’s book… too much on pictures and forecast. (Full disclosure, I had asked this question to him.)

    [Response: I think George Philander’s book “Is the temperature rising” is quite good, and David Archers “Understanding the forecast” is even better. For a really full treatment though, you have to go back to physics texts on radiative transfer. Dennis Hartman’s book ‘Global PHysical Climatology” is also excellent. For a really complete start-to-finish yet quite accessible (if you can handle a few equations) is RC’s own Ray Pierrehumbert’s book– really excellent, I might add — that is in proof form on this web site, here

  3. 103
    TD says:

    98 – Thanks… Just what I think I am looking for!

  4. 104
    William T says:

    @ Mark Gibb – the obvious reason why protagonists on both sides of this debate end up resorting to ‘alarmist’ scenarios is that otherwise nothing would get done. People (and politicians) are only going to agree to massive inconvenience if there is a really serious threat. Face it, this has to be a political issue because it is politicians who will decide on the changes needed to respond to the scientific evidence. The impact of that evidence has to be spelled out in terms of ‘alarming’ dangers in order to stir the politicians into action. (and of course on the other side, the downsides of action have to be made very ‘alarming’ in order to stir up opposition).

    Otherwise it is merely yawn-inducing scientific arguing points that most people will care nothing about.

  5. 105
    Bud says:

    @TD 102: as another “neophyte” I’ve started working my way (slowly, I’m a final year student so swamped enough already!) through Ray’s book, and I can fully recommend it.

    Eric, I honestly sympathise with that crap you just had to put up with from oracle2world. I’d leave that up as an example of why moderation on some blogs is needed. I come here to learn from experts (both above and below the line) and to see a reasonable subset of critical comments from those outside the consensus. Not to read pages and pages of that nonsense. That kind of post is why few people bother to argue at the Guardian blog anymore.

  6. 106
    Patrick 027 says:

    Re 97 myself (Re 46 Ryan O) –
    “maybe if you measure height from the tropopause, the two equilbrium temperature profiles above the tropopause (setting aside seasonal and regional variations) would match up or roughly so (?concievably?),”

    Actually, my impression has been that the tropopause level itself will be higher and colder at new GHG-forced-warming equilibrium, so …

    (Specific results may vary based on spectra and concentration variations (water vapor, ozone) of gases, and of course, cloud feedbacks, etc.)

  7. 107
    Journeyman says:

    Ike Solem, regarding daily high low temperature records, I would not expect the number of these record to be same, when I know the average current temperatures are higher than at the start of my instrumental record period. Given 100 years of lower temperatures, I would be shocked at the number of low records being found. If temperatures stayed in equilibrium after 100 years of warming, what ratio of highs to lows would you expect to find?

  8. 108
    Journeyman says:

    How is this different from the Copenhagen Synthesis Report?

  9. 109

    I am sure all GC models are geared up better since the 80’s, but El-Nino not flaring up like in 1997-98 with the same strength fascinates, and I wonder if there is a plausible explanation of its relative quiesence. Which is useful, since despite a weaker El-Nino than 1997 GT’s are warmer… There is some sort of synergistic convergence which creates strong El_Ninos, much a do with natural variability, would be nice to know what triggers a massive event. Surely 1997-1998 el-nino will be surpassed one year, but , in other words, what is stopping it from happening again?

  10. 110

    Nicolas Nierenberg #81, #87, #95:

    I read what you wrote and it looks generally OK, but one problem. Yes, cross-validation as done is a good way to find out if a relationship found is real, and how good it is, but note that in this case, the relationship is tested using only half of the data points. This means that you may not transfer back the conclusions unchanged to the fit based on all data points.

    If you do a linear regression, and then remove half of your data points, everything else unchanged, the standard error of your slope goes up by sqrt(2). If additionally, you shrink the span of values for the temperatures T and sea level rise rates dH/dt also by a factor of roughly 2, that adds a further 2x to the slope uncertainty. Totalling 2*sqrt(2) = 2.8x.

    Now let’s take your values 0.42 and 0.24 for the slope estimates from the two halves. Express it as 0.33 +/- 0.09. To carry over the uncertainty to the full data fit, you must divide by 2.8, yielding 0.33 +/- 0.03. 10% relative uncertainty. This is one-sigma only; climatologists seem to always want to see two-sigma, or 5%-95% bounds…

    Yes, the half-data fits are very uncertain and sensitive to small changes in method. This is not surprising: consider that 15-year smoothing was applied, so the number of independent data points in them cannot be more than 4, likely less, considering autocorrelation. And from that, you try to estimate two parameters. No surprise really.

    Unrelatedly, one problem with R07 that no critic seems to have hooked onto is, that it uses the language of hypothesis testing when it is actually doing nothing of the kind. Everybody seems to do that: the commenters on R07; even the IPCC, causing much head-scratching (google “silly nulls”; “the greenhouse effect doesn’t exist” is no less silly than “temperature doesn’t affect sea level”). Scientists doing what they learned in school and know how to :-)

  11. 111
    isotopious says:

    Figure 21, page 52.

    This is probably the worst figure I have ever seen. Look at the units!
    All the degrees centigrade are making me dizzy.


  12. 112
    Terry says:

    Eric…Thanks for your time on here. I understand atmospheric physics and the models pretty well, but I struggle with the concept of Antarctic Ice loss. I do understand WAIS loss by calving at the sea/ice interface if the sea temp is high enuf, but glacial loss has me stumped when it is below zero, unless is is mechanical due to a loss of ice at the sea interface. If you could point me to a robust backgrounder that includes the thermodynamics and correlations of sea/air temps with ice loss, I would be vey grateful. Many thanks

    [Response: First off, don’t confuse land ice and sea ice (I’m not saying you are, but I can’t quite tell as you’ve not being specific). I assume we are talking about land ice here. Second, the calving is all mechanical. Water temperature doesn’t matter (it’s always right about at freezing at the ice margin!). There are plenty good references on all this, but a great place to start is probably with The Physics Of Glaciers (Stan Paterson), readily found on Amazon or whatever. Hope that helps –eric]

  13. 113
    Ben says:

    Is it too much to ask for an html version with links to references and references hyperlinked to original articles or abstracts online? Peer-reviewed journals do that, why can’t you? And it’s not too hard to get hyperlinks in pdf. This report looks like an advertising brochure.

    [Response:Journals have staff and budgets to pay them for this sort of thing. We’re working in our spare time. If you’d like to do the work for us, we’ll gladly upload the finished project to the website.–eric]

  14. 114
    HR says:

    Anybody answering questions on the ‘science’ in this document? Because I have one.

    In the CO2 section it’s states that the rate of production of human CO2 has increased since 1990. It also says that the amount of CO2 absorbed by the natural sinks has fallen (by 5%). When you look at the graph that shows CO2 in the atmosphere in ppm you see a linear increase in this for the past 50 years.

    My question is if the first two points are correct you would expect to see CO2 accumulating in the atmosphere at a faster rate in recent times but the linear nature of the ppm graph suggests a steady rate of increase over 50 years. What am I misunderstanding here?

  15. 115
    Guy says:

    Eric – would be grateful if you could comment on #69, even though #84. My post in #69 comes right out of the report itself – some further detailed comment on context would undoubtedly help how this report is perceived by the public. Communication of science to the public is the raison d’etre for RC, isn’t it?

    So can the public objectively rely on the report’s conclusions as being a completely representative cross section of the climate science academic community, or is it a subset? I can’t think of a more important, or timely question to answer, and the lack of one does great harm imho.

    [Response: Are the report’s conclusions ” a completely representative cross section of the climate science academic community”? Probably not. This report didn’t go through the same level of review as did IPCC. Did we do our level best to make it representative? Yes. Why should you trust what I’m saying? Well, you don’t have to. You could go ask any of the other others (all 23 of them) who are *not* part of RealClimate. Or you could ask various people who are not even on the author list. Take a sample, see what you come up with. No doubt you will find people who will quibble with some details, but for the overall picture, and the major conclusions….I think the results of such a survey will restore your confidence.–eric]

  16. 116
    Didactylos says:

    HR (#114):
    The rate of increase is much easier to see if you look at a longer timescale. The report only shows 30 years (I would guess for consistency with the CH4 graph). Tamino has an excellent discussion of this, with his usual statistical analysis: CO2 Acceleration. He calculates that the acceleration is is about 0.025 ppm/yr/yr.

  17. 117
    Anne van der Bom says:

    Mark Gibb,
    24 November 2009 at 2:08 PM

    You seem to have made up your mind firmly before reading the report. Why waste time reading it?

  18. 118
    viento says:

    Why is the review paper by Milne et al, Nature Geoscience 2009, which also disagrees with Rahmstorf 2007, not even cited?

    [Response:That paper is an assessment of the causes of sea level change, not a paper on projections. And it doesn’t disagree with Rahmstorf. They say “We find that most studies constrain global mean sea-level rise to less than one metre over the twenty-first century…” and “For example, a recent study concluded on a sea-level rise of 30–80 cm by 2100 in northwest Europe. It is possible that in specific areas, the upper bound could be significantly higher…” Both these statements are in complete agreement with the mean (<1 m) and high end (>1m, but << 2m) of Rahmstorf (2007) and the several others studies we cite.--eric]

  19. 119
    greg kai says:

    Where is the “benefits” section in their cost/benefits analysis of future warming consequences? Or is there really no benefits involved? This means that we live (lived?) in the best of all possible worlds regarding temperature, sea level and other global environmental conditions??? I am glad that the report authors are so fond of Leibnitz…

    Seriously, there is no cost/benefits analysis analysis, it is exclusively an analysis of risks linked to projected temperatures. It is of course ok to do that, but I do not believe that it makes a correct summary for decision makers, as it, by definintion, paint a one-sided picture.

    My other gripe with the report is that it simplify the solar forcing to the single issue of global energy flux from the sun and it’s (very slight) variation. The hypothesis from the solar camp consider other parameters (spectrum, magnetic field variations), whose influence is much less direct (and hence much less clear), but on the other hand have much more variation accross solar cycles…

    [Response:Regarding risk analysis, I refer you to IPCC Working Groups 2 and 3, neither of which we claim to be updating here. And you might look at e.g. Battisti and Naylor in Science if you want to consider risks. As for the arguments made by the ‘solar camp’, they have not been convincing at all, as we have discussed at length. The evidence *against* the solar component being a major player is overwhelming. We do not claim that the Copenhagen Diagnosis is a comprehensive summary of all possible arguments ‘for’ or ‘against’. It is a summary of major new and convincing data. There has been nothing new or convincing from the solar camp.–eric]

  20. 120
    gbettanini says:

    Sorry but i can’t well understand the figure #16 about the sea level rise.
    The interpolation of the satellite observed rise indicates a level increase of about 35 cm every 100 years. The highest prediction of the rise from IPCC is around 60 cm every 100 years. So i think that the ‘IPCC Predictions’ zone must be higher than the zone displayed in figure #16.

  21. 121

    Chip: If models were getting things right (including weather noise), then the observed trends would be contained by the models at all time frames.

    BPL: Your “then” is a non sequitur. You’re confusing climate with weather.

    Chip: That they are not, is a robust result that the models (or at least some of them) aren’t working right.

    BPL: Wrong again. The models give projections for climate, not weather.

  22. 122
    Stuart says:

    Thanks for your response to comment #43:
    “Those calculation were done “Keeping everything constant except for the CO2 concentration.” They don’t take into account the water vapor feedback (or any other feedbacks).–eric”

    But isn’t it true that feedback is not understood and cannot be measured directly? I’m a non-climate scientist (originally an infrared spectroscopist) – I’m trying to get a handle on what all the assumptions are that have been made in inferring the predicted changes.

    See recent essay here by Roy Spencer:
    Despite the fact that the magnitude of anthropogenic global warming depends mostly upon the strengths of feedbacks in the climate system, there is no known way to actually measure those feedbacks from observational data.

    The IPCC has admitted as much on p. 640 of the IPCC AR4 report, at the end of section 8.6, which is entitled “Climate Sensitivity and Feedbacks”:

    “A number of diagnostic tests have been proposed…but few of them have been applied to a majority of the models currently in use. Moreover, it is not yet clear which tests are critical for constraining future projections (of warming). Consequently, a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.”…….
    And until such a test is devised, the warming estimates produced by the IPCC’s twenty-something climate models are little more than educated guesses.

    [Response: There are a number of papers which address the issues you bring up. For example, “Knutti, R. and Hegerl, G. C. [2008]
    The equilibrium sensitivity of the earth’s temperature to radiation changes Nature Geoscience ; 1 ; 735-743 “–eric]

  23. 123

    Jim Bullis: You can’t be serious that pV=nRT applies after millions of years of adjusting.

    BPL: Huh? What? Come again?

    Why would the ideal gas law stop working?

  24. 124

    Jere Krischel: What evidence do you have that a warmer world is worse for people,

    BPL: The fraction of Earth’s land surface “severely dry” by the Palmer Drought Severity Index was 12% in 1970. By 2002 that figure was 30%. Ask the Australians about global-warming-induced drought.

    Ref: Dai, A., K.E. Trenberth, and T. Qian 2004. “A Global Dataset of Palmer Drought Severity Index for 1870–2002: Relationship with Soil Moisture and Effects of Surface Warming.” J. Hydrometeorol. 1, 1117-1130.

    A billion people in Asia and Latin America depend on glacier melt for fresh water. The glaciers are receding fast. India and Pakistan have already exchanged fire and had troops killed over which side owns a glacier.

    JK: especially since we’ve already had that in the medieval warm period?

    BPL: No, we have not. The MWP was cooler than now:

    Bradley, R.S., Hughes, M.K., and H.F. Diaz 2003. “Climate Change in Medieval Time.” Science 302, 404-405.

    Goosse H., Arzel O., Luterbacher J., Mann M.E., Renssen H., Riedwyl N., Timmermann A., Xoplaki E., Wanner H. 2006. “The Origin of the European ‘Medieval Warm Period’.” Clim. Past, 2, 99–113.

    Osborn, Timothy J. and Keith R. Briffa 2006. “The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years.” Science 311, 841-844.

  25. 125

    dfree: Funny, but I never read any info here,that includes the contribution natural events may have in the spike of CO2 measured in the last 60 yrs? A spike of some 50 “p.p.m.”

    BPL: Try here:

    Revelle, R. and H.E. Suess 1957. “Carbon Dioxide Exchange between Atmosphere and Ocean and the Question of an Increase of Atmospheric CO2 During the Past Decades.” Tellus 9, 18-27.

    Suess, H.E. 1955. “Radiocarbon Concentration in Modern Wood.” Sci. 122, 415-417.

    dfree: like ..say “volcanoes”…I feel they have been over looked and not included in the equation of the composition of the aggregate amount of CO2, measured to date..that is attributable to human activity! last count was less then 4%!!..seem rather small to be getting excited about..or even re-engineer the last 12o years of how this country does business?

    BPL: Try here:

  26. 126
    NeilT says:

    It is claimed that this report is alarmist, that the tone and tenor of the report overstates the case and that the impacts of Global Warming will be much more benign than stated in the report.

    I see the short version as this. This report summary says nothing about storm intensity, surges or impact of even moderate storms in a world where sea levels are changed by warming. It does state that storms are getting worse, but that is only part of the picture. It says nothing about the sea defences which will be overwhelmed and people constantly talk about a 1M sea level rise as if it is static.

    Looking at the royal society report on the 1953 East Coast flooding in England and the Netherlands

    and the comments about the lack of calculation of sea level rise in the sea defence design, it is guaranteed that it will not take hurricanes or typhoons to inundate the land and kill people in 50 years time. It will simply take a 50 or 100 year storm. Which, if we are to believe the predictions, will be much more frequent.

    The report could have, quite easily, stated that displacement from storms would become more frequent and that significant portions of arable land would be lost to saltwater contamination for periods of years; damaging the food supply.

    Given that 100 year storms will come around every 70 years (or less), and it will only take 30 or 50 year storms to do the same damage as 200 year storms; with the sea level rises, I think the report is actually understating the impact of Global Warming and sea level rise by quite a large degree.

    And that is without the demographics of people moving to coastal regions with at risk areas seeing 30-90% increases in population increase based upon the “security” of these se defences.

    When we it starts to hurt, we won’t have 25 or 30 years to engineer solutions. We will have months. The best defence is not to go there in the first place.

  27. 127
    jean claude says:

    It’s okay to admit that there are some things we don’t know. That at our current level of understanding, some systems are beyond our complexity horizon.

    This does not mean that what we think we know is wrong. It also does not mean that what we think we know is right.

    Some variables are well defined, some are poorly defined and others are either ignored or unknown. The result of any honest AGW model is a very low degree of confidence. Degrees of confidence can not even be honestly calculated because of all of the unknowns and poorly understood variables.

    This is where the real dispute lies within the scientific community: Do we include all variables, those known and well understood; those that are moderately or poorly known; and those that remain unknown except in the sketchiest of details?

    If you deal only with those variables that are well known you can make predictions with what seems like a high degree of confidence, but how reflective are they of the actual system as it exists within nature?

    Any theory at this level of development can show promise in shedding light on the direction of future research. What it cannot do nor should not do is use such a poorly understood complex system as a platform to pontificate on public policies that will affect billions of lives and trillions of dollars.

  28. 128
    Dale says:

    This may be deleted but I know from my upbringing among denialist types (My father was a McCarthy apologist) that their reality is not based on facts but rather on factoids. They have about as much affinity to science as Little Abner has to Harvard. What they believe is unfettered capitalism is a pure and clean as the fresh driven snow and that any inconvenient truth no matter how compelling will never be accepted.

    I really appreciate what Gavin, you and others have to deal with. I see a mob mentality out there among the anti AGW crowd (To be honest there are a few with the ability to give and take but not many) and they remind me of the mob going off half cocked that drove Ryan White, the young AIDS victim from his school in Kokomo, Indiana in the 80’s.

  29. 129
    Richard Steckis says:

    Eric says:

    “Response: That’s the point. There are *costs* associated with global warming.–eric”

    There are both costs and benefits associated with any climate change whether man induced or not. That is the nature of changing ecosystems.

    You are anthropomorphising.

  30. 130

    The “Copenhagen Diagnosis” looks to me, a lay reader, to be a very well-produced and comprehensible update. I hope it receives a very wide distribution in the next few weeks.

    One thing confused me on p38. “The CO2 content of the oceans.. continues to increase by about 2 Gt per year (Sabine et al, 2004)” I’ve been quoting to people that CO2 (not carbon) emissions are about 26 Gt per year, and that up to a third of emitted CO2 is currently able to be absorbed by the oceans… which would be more than 8 Gt pa. Does this perhaps mean 2 Gt carbon rather than CO2? (And should we standardise on using carbon, CO2, or CO2e?) Alternatively, is the 2 Gt a net balance because some dissolved CO2 precipitates into insoluble carbonates or is taken out of solution by biological calcification?

  31. 131
    Ray Ladbury says:

    HR, Do a Taylor expansion of exp(t/t0). Now make delta t/t0 very small, and the linear term dominates. That does not, however, negate the fact that the increase is exponential. Likewise, look at interest on your CD. Over short times, the returns look constant. Only over longer terms does the compounding kick in. Make sense now?

  32. 132
    Ray Ladbury says:

    Isotopious @111

    Yeah, math is scary, huh!

  33. 133
    Alan Millar says:

    The whole basis of the cause of some of the observations described in the Copenhagen paper is completely unresolved at this time in my opinion.

    One of the most interesting of the leaked e-mails is, to my eyes, the one which iincludes reference to the 1910 – 1940 ‘problem’.

    “It would be good to remove at least part of the 1940s blip,
    but we are still left with “why the blip”.

    Let me go further. If you look at NH vs SH and the aerosol
    effect (qualitatively or with MAGICC) then with a reduced
    ocean blip we get continuous warming in the SH, and a cooling
    in the NH — just as one would expect with mainly NH aerosols.

    The other interesting thing is (as Foukal et al. note — from
    MAGICC) that the 1910-40 warming cannot be solar. The Sun can
    get at most 10% of this with Wang et al solar, less with Foukal
    solar. So this may well be NADW, as Sarah and I noted in 1987
    (and also Schlesinger later). A reduced SST blip in the 1940s
    makes the 1910-40 warming larger than the SH (which it
    currently is not) — but not really enough.

    So … why was the SH so cold around 1910? Another SST problem?
    (SH/NH data also attached.)”

    This 1910-1940 issue goes to the heart of what level of confidence we can have in the AGW theory and the associated GCMs.

    Upto now it seems that certain AGW scientists and advocates have been happy to wave their hands a bit whilst muttering Solar and Aerosols as the answer as to why global temperatures increased at a similar rate during this period as compared to the latter part of the century, with little help from increasing CO2 levels.

    I have known all along that this is rubbish. If you believe in AGW then you can only allow a small fraction of the observed increase in temperatures to be attributable to increased solar activity. As far as aerosols go this is a direct lie. Aerosols increased very sharply during this time. This is a fact confirmed by the Greenland ice cores.

    Now we can see, in writing, that this problem is unresolved by scientists at the heart of the AGW hypothesis and they do no believe the meme they have happily allowed to become established as the answer to this ‘problem’.

    So we know for certain that we have a situation where an unknown combination of climatic factors caused the global temperatures to rise at a significant rate comparable to the late 20th century and this remains unresolved.

    I am sure that most people here can see what this means for the AGW hypothesis. Logic dictates that if you cannot explain one rise over a similar period then you cannot explain another rise over a similar period. Unless you can identify and isolate the significant factors in the earlier period then you cannot know whether these unknown factors are driving the rise in the latter period, it is unarguable logic.

    This disconnect has been hidden in my view. It needs to be addressed and made known and highlighted in all discussions with policy makers etc. Willful failure to do so would be similar to sticking fingers in your ears and going “La La La……”!

    I would appreciate someone at RC addressing this issue and justify pushing ahead with very costly change to society whilst this huge issue lies unresoved at the heart of the AGW hypothesis.

    Please don’t give the glib answer that ‘Just because we don’t know everything, doesn’t mean that we know nothing’ Can there be a more fatuous and vacuous statement when it comes to science?

    Is there any other area of science that would give a free pass to a theory that had huge uncertainties, unresolved crucial issues and downright conflicts in emperical observations at the centre of the arguement just by using the phrase ‘Just because…….’?


  34. 134
    Paul UK says:

    Re: comment 8: sascha

    Sascha. I live near a city that is at risk of flooding, Portsmouth, Hampshire, England. Most of it is barely 5 metres above sea level and many parts are barely a metre or two above sea level. I recently took the bus down to Gun Wharf Quays and noticed the high tide mark around the bottom of the Millenium tower. Then I noticed that where I was standing was barely 1.5 metres above the high tide mark.
    This development was finished a few years ago. It’s going to be flooded (along with the posh quay side shops) in a few decades, does that make sense to you?

    Maybe in the time scales that consumerism is based on, then anything beyond a decade or two is a long time. But we can’t think like that any more.
    Portsmouth has a population of 200,000. Where I live it is a problem finding land to build 2000 homes let alone tens of thousands. We are already building on farmland here, rehousing Portsmouths population is going to be horrendous and I doubt any suitable sea defence will work.

  35. 135
    tharanga says:

    Is my eye playing tricks on me, or did somebody misspell Pielke as Piekle on p21, and the reference list?

  36. 136
    tharanga says:

    Regarding Antarctica, “Antarctica is not cooling: it has warmed overall over at least the past 50 years.”

    I haven’t read your paper yet (Steig et al), but referring to the figures here, , one can see cooling in East Antarctica in the time period of the ozone hole (as the report also mentions, but doesn’t show graphically). In the period since 1969, what is the trend for the entire continent? To my eye, it looks like the warming in West Antarctica and the Peninsula outweigh the cooling over the larger area of East Antarctica, but spatial averaging by eyeball isn’t very robust.

  37. 137
    Ike Solem says:

    Climate science update: from bad to worse

    by Staff Writers
    Paris (AFP) Nov 24, 2009
    “The planet could warm by seven degrees Celsius (10.8 degrees Fahrenheit) and sea levels could rise by more than a metre (3.25 feet) by 2100, scenarios that just two years ago were viewed as improbable, scientists said on Tuesday.”

    “In the widest overview on global warming since a landmark report by the UN Intergovernmental Panel on Climate Change (IPCC) report in 2007, the authors said manoeuvering room for tackling the carbon crisis was now almost exhausted.”

    A search of the NY times reveals no coverage of that story, just more articles on the “sinister emails” – and no condemnation or discussion of the sinister breach of security, or why they sat on the story for over a month before running it right before Copenhagen. You would think they would be embarrassed – maybe not being fired is a more important consideration – just look at what happened to CNN’s entire science & tech news team when they started running reports on global warming? Fired within six months.

    A search of the BBC reveal no coverage of that story either, just more on the climate emails – and an effort to respin their severe flooding as completely unrelated to climate change:

    No, this seems to be much closer to what insurance brokers sometimes call “an act of God”. Forgive my imperial education, but more than a foot of rain fell in Seathwaite Farm in just 24 hours!

    An Act of God? I think there’s a good argument that dumping billions of tons of fossil fuel CO2 into the atmosphere for over a century is responsible – and Britain has always been a world leader in fossil fuel development, so it’s hard to claim that it wasn’t something that they themselves had a big hand in, unwittingly enough.

    What the BBC neglects to report is that Britain had similar floods two years ago – and as now, the government declared them to be a “once in a lifetime event.” Once in a lifetime? Once in a thousand years? A 500-year flood?

    London’s Financial Times had an interesting interview with some climate scientists:

    “He believes that changes in rainfall patterns will have the most direct impact on people’s lives. In simple terms, he says, “the wet places will get wetter and the dry drier”. In the Mediterranean – one of the easiest regions to model – a 3°C temperature rise would cut rainfall by 20 per cent.”

    Compare that to British tabloids, which are printing glop like this:

    “Much more likely is that these floods and droughts are caused by old-fashioned, run-of-the-mill climate change of just the kind that occurs no matter how many cheap flights we take or how little we recycle.”

    Yes things just happen – why? Divine influence – yes, it is mysterious. Sacrifice a goat and pray for the rain to end, that’s my advice.

  38. 138
    pete says:

    “[Response: No, what you are doing is cherry picking. Those who work on sea ice understand perfectly well the vast differences between Arctic and Antarctic sea ice. The reason I assumed IPCC hadn’t done projections for the Antarctic is because I know (and the IPCC authors, of which I’m not one, know) that we can’t do that with any reliability. Antarctic sea ice (unlike Arctic) is a question of winds, and thermodynamics barely come into it, which makes it quite a lot harder. Again, there *is* a section on Antarctic sea ice, and it is perfectly clear, and accurate. You are looking for things to complain about. Any fool can do that, and most fools do.–eric]”

    Are you saying the Arctic sea ice is not subject to winds? If you honestly believe that, how can you explain the behavior of the ARCTIC sea ice the last 4 years. Going down to an historic (since 1973 satellite age, any other conclusion has absolutely no merit or evidence to the contrary) minimum, and now a scant two years later, the minimum extent has increased by well over 1 million km2.

    From NASA’s own website you get this quote……Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic,” he said. When that sea ice reached lower latitudes, it rapidly melted in the warmer waters.


    Please cite some literature which contradicts the quote from NASA above and this quote which seemingly explains the ‘histroic’ loss of Arctic sea ice this century….””The winds causing this trend in ice reduction were set up by an unusual pattern of atmospheric pressure that began at the beginning of this century,” Nghiem said.

    [Response: Sigh.. I never said Arctic sea ice isn’t affected by winds. What I said was the Arctic sea ice is expected to be more predictable than Antarctic sea ice. The question was about Antarctic sea ice. Read the report, it is very clear on the Antarctic sea. If you still have questions *after* you have read it, I am happy to try to answer them. Accusations of my ‘not telling the truth’ are not, by the way, appreciated.–Eric]

  39. 139
    Thomas says:

    At first I thought it was pretty good and compelling. But having slept on it I think there are some things missing.

    (1) The treatment of the way GHG cause warming was too simplistic (although a marvelous mental device to aid understanding). The obvious problem is that GHGes don’t operate as grey absorbers, so in some frequencies an IR photon emitted at the ground has a high probablity of directly escaping to space, while another whose frequency matches a strong absorption line will travel only a short distance. This observation combined with the line shape gives the logarithmic dependence on concentration…

    (2) GHGes other than CO2, and methane were barely mentioned. The fact that some novel (to the atmosphere) compound whose absorption bands/lines lie within the atmospheric windows can produce a hugely disproportionate forcing is important to understand. Clearly some of these industrial chemicals provide an important point of leverage for modifying the total anthropogenic forcing. Of course it needs to be emphasized that controlling the other GHGes alone will not prevent severe climate change. But ignoring them will lead to even greater anthropogenic forcings.

    Of course, some sort of balance between full detailed understanding and simplicity must be made to serve the wide audience for which this document is intended. I just think a few more details for the more technically inclined readers might have been in order.

  40. 140
    JBL says:

    @Eric: your response in this post (currently #23) is all kinds of garbled — what were the parts that got cut off?

    [Response: Fixed.]

  41. 141
    mauri pelto says:

    Ice loss when the temperature is below zero is dominated by the aforementioned calving which is easily observable, and the less observable and quantified basal melt by ocean water under the ice shelf. Under some ice shelves there is refreezing as well. Melt rates have commonly been observed to be over 10 meters per year.

  42. 142
    mike roddy says:

    This is a great report, especially the data graphs, and it should be sent to every news outlet and public school in the country. It’s clear, decisive, and urgently needed.

    My main quibble is the same one I often bring up: “Deforestation” should not be preceded with “Tropical”. Boreal and even US forest sinks sequester more carbon per acre, and are leveled just as relentlessly as in the tropics. Tree farm replacements are inadequate in terms of recovering soil and other biota, and are already showing poor survival compared to mature forests in terms of fire and pests.

    The reason scientists overlook this is that the US and Canada still have net forest CO2 sequestration due to their great size. This is already changing in British Columbia, and will soon change in the Rockies. In any case, net sequestration could be far higher if we slowed our profligate wood consumption and began to use truly sustainable foresty practices.

  43. 143
    pascal says:

    Hi Eric

    I think there is an error in the scale unity of the fig9
    (The Greenland melt area).
    It is not 10^6 km2, but 10^5km2.

  44. 144
    Chris Dudley says:

    I feel that the report does not cover adequately indications in the fossil record that sea level rise can occur very rapidly so that the 2 meter upper limit for 2100 may be spurious. AR4 did a better job of caveatting on this issue though there is was still too weak. Suggestion that mass loss in the East Antarctic Ice Sheet is accelerating by Chen et al. this week underscores that an upper bound for sea level rise this century is very hard to set.

  45. 145
    doug bennion says:

    Gavin this is germane to the properties of pop-up window itself, not the topic being discussed. When I follow a link, the window does not resize to fit the new link, and I cannot resize it myself, so have to scroll up and down and side to side. It’s just a mild irritant, and maybe nothing you can do about it, but sizeable would rock. Thanks.

  46. 146
    eric says:

    Comments are now turned off. Unfortunately, the comments are now running about 10:1 insults and innuendo. Serious discussion seems to have largely died off. The last couple of posters did raise some reasonable questions, and I will respond to them after Thanksgiving. Meanwhile happy Thanksgiving to all the American readers (and to everyone else, for that matter).–Eric