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Copenhagen

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 www.copenhagendiagnosis.org. 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. 1
    Bill says:

    In view of this impending potential disaster and the syated need for urgent actions, I would suggest that >95% of the planned attendees at Copenhagen cancel their trips, stay at home and use the internet and save untold amounts of CO2. The need to set examples needs to start here !

  2. 2
    James Allan says:

    Nice work. One thing I like is the big emphasis on observational data; thinking back to the the time of TAR, one of the most common (largely misguided) complaints from the sceptics was that climate science entirely relied on models and that the of the prophesies of doom were nothing more than hyperbole. Now that we have so much more data, that line of argument is more or less defunct and I think the balance in this report is a good reflection of that.

    [Response: Thanks, yes. I think that is a real strength to the report. The raw observations speak pretty loudly, and as Lonnie Thompson likes to say, the data have no political agenda.--eric]

  3. 3
    DavidCOG says:

    The perfect response to the stolen emails sideshow.

    Thank you to all the hard-working, serious scientists that contributed and who are helping us understand what is happening to the climate.

  4. 4
    David Hutton-Squire says:

    Instead of the non-existent http://www.copenhagendiagnosis.org/ under the logo at the top, you clearly meant http://www.copenhagendiagnosis.com
    Thanks for the (almost) pointer.

    [Response: Works fine. There may have been some delay in the updating of .com-->.org after the initial release.--eric]

  5. 5
    Chris Dudley says:

    I found the projection of a 40% loss of permafrost by 2030 regardless of emissions scenario to be something that could use more discussion. This seems like a large potential feedback in the near term that should be quantified. What would happen if we stabilized at 350 ppm early, say in the 2040′s? There are emissions scenarios that have not been explored yet.

  6. 6

    Eric,

    As you may or may not know, I am currently working on trying to properly compare observed global temperature trends during the past 5-15 years with model projections during similarly short periods—a less than straightforward endeavor. So I am somewhat familiar with the behavior of recent temperatures.

    The CopenhagenDiagnosis seems at odds with at least my interpretation of recent events. For instance, try as I may, I cannot seem to reproduce Figure 3 (top) from the CopenhagenDiagnosis report from the tool for plotting temperature trends available at NASA GISS. For one thing, I am not sure why the report which is intended to provide the most updated information only shows the trends (in Fig 3top) through 2007, when annual data through 2008 is readily available from GISS (in fact Fig3 bottom uses data through August 2009). But whether I use data from 2001 through 2007 or 2008, the trends map I produce from the GISS site is much different from the one depicted in their Fig 3 top. Perhaps I am doing something wrong.

    And the general handling of whether models are correctly capturing recent temperature changes is given a rather less than robust handling in the section “Has global warming recently slowed down or paused” (p. 15). The observed temperature behavior is a bit less simple than presented (for example, see my discussion here). And only about half the difference in short-term temperature trends between the GISS and the CRU data can be explained by coverage differences (so the difference is not as readily swept under the rug as the CopenhagenDiagnosis indicates). Further, there is virtually no discussion about how well models capture the shorter-term temperature trends, say during the period 2001-present (the period depicted in Figure 3 top). During this period, it is less clear that the models, which include natural variability, are accurately capturing what is going on. For instance, Knight et al. (BAMS 2009), which has overly wide confidence intervals because they include variability besides weather noise, show that the observed trend falls out on the lower shoulder of the HadCM3 projected trends. In my investigations, some other climate models don’t fare as well as the HadCM3 (nor does the HadCM3 fare as well when variability is properly constrained).

    So, in my view, the point that you highlighted “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” is not well-supported.

    -Chip

    [Response: Chip: Why on earth are you trying to "compare temperature trends during the past 5-15 years with model projections during similarly short periods". That's a pointless, fruitless, silly exercise. Models reproduce well the statistics of stochastic climate variability, not the details. Homework: Read page 13 of the report again.--eric]

  7. 7
    sascha says:

    First, I’d like to thank the authors for taking the effort to present the facts in such a way that non-scientist like myself can understand them. Also, thanks for making the whole report available online and free of charge.

    Still, I was a little disappointed:

    Just when I was convinced I was actually reading a non-alarmist, non-political fair summary on the most recent state of knowledge of climate science, I came accross page 51 (chapter “The Future”) where it says:

    “[...] global mean warming of even just 1.5-2.0°C still carries a significant risk of adverse impacts on ecosystems and human society. For example, 2°C global temperature rise could lead to sufficient warming over Greenland to eventually melt much of its ice sheet (Oppenheimer and Alley 2005), raising sea level by over six meters and displacing hundreds of millions of people worldwide.”

    …even though page 31 (chapter “Global Sea Level”) clearly states two meters as the upper (!) limit for 2100.

    So I assume this means the “six meters” mentioned here could, if ever, only be reached gradually over the course of several centuries or even milennia into the future – a time span for which:
    a) no credible meaningful climate predictions can be made, even with todays most sopisticated computer models (please correct me if I’m wrong), and
    b) for which “displacement” is a rather nonsensical concept, as over the course of many generations, civilisation and the way it uses the earth’s surface will gradually evolve/shift anyhow and no individual will nececcarily ever be “displaced” by this shift.

    Therefore, I feel that even though it might be scientifically correct that 100% of Greenland’s ice melting would theoretically correspond to 6 meters in sea level rise, it’s rather dishonest to phrase it like it was in the report, pretty much using it as an excuse for introducing the alarmist notion of iminent massive human tragedy.

    I can already picture in my mind tons of press releases/articles by Greenpeace, Time magazine, etc. where the only words they will quote from the this report will be:
    “raising sea level by over six meters and displacing hundreds of millions of people worldwide”.

    Was this really necessary?

    [Response: Not every sentence in the report is going to please everyone. But there's nothing 'alarmist' here. 'Merely' 1 m by 2100 is going to have a huge impact, itself displacing hundreds of millions of people. And yes, 'displacing' is exactly what we're talking about (people will have to move to another place). And it's not just the third world either. Ever flown into Vancouver, BC? You'll still be able to land at the Vancouver airport after 1 m of sea level rise .... if you have a seaplane. Finally, tme will keep marching forward past 2100. --eric]

  8. 8
    DrCarbon says:

    Eric, Looks like your time stamp is off as this was posted under Nov 21 instead of Nov 24. FYI.

    [Response: Fixed, thanks.]

  9. 9
    dhogaza says:

    So I assume this means the “six meters” mentioned here could, if ever, only be reached gradually over the course of several centuries or even milennia into the future…

    Well, yes, that’s what “eventually” vs. “by 2100″ means. Clear as day to me.

    Therefore, I feel that even though it might be scientifically correct that 100% of Greenland’s ice melting would theoretically correspond to 6 meters in sea level rise, it’s rather dishonest to phrase it like it was in the report, pretty much using it as an excuse for introducing the alarmist notion of iminent massive human tragedy.

    You’re reading something into it (“imminent”) that’s not said. I suppose they could preface each paragraph with “please read carefully and take care not to misconstrue what we say”, but even that probably wouldn’t prevent misreadings.

  10. 10
    sascha says:

    Well, yes, that’s what “eventually” vs. “by 2100″ means. Clear as day to me.

    As long as “eventually” is not defined in any way, it isn’t that clear to me.

    You’re reading something into it (”imminent”) that’s not said.

    Well, they do use the statement in the context of warning about mass “displacement” – a phrase that implicitly carries with it the connotations of “catastrophe” and “short time span” (as I stated before, it doesn’t make sense when looking at long time spans).

    That’s what I ways trying to say.

    [Response: Sascha: Fair enough, and I appreciate your balanced tone. However, you should recognize that while it is virtually certain that business as usual scenarios will eventually destroy the Greenland ice sheet, the timescale for this remains very uncertain. So all we can really say at this stage is "eventually". We don't use the word "catastrophe", and I agree that would be a loaded an inappropriate term.]

  11. 11
    dhogaza says:

    Well, they do use the statement in the context of warning about mass “displacement” – a phrase that implicitly carries with it the connotations of “catastrophe” and “short time span”

    Short time span when they explicitly discuss two meters, not six meter, as the maximum possible sea-level rise by 2100?

    C’mon … it’s obvious that “eventually” means “long after 2100″, in context.

    Of course, I’m a native speaker of English, while the name “sasha” implies that maybe you aren’t, but still, you’re adding a lot of personal prejudice into the words that were actually said.

  12. 12
    pete says:

    I think Jaxa might diagree with your Arctic Sea ice declining mantra….minimum this year over 1 million sq km above 2007 and second straight year of recovery………..
    http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

    [Response: The relevant part of that figure is where 2009 intersects with Sept -- around 5.5 million km2. Put that data point on the graph (Figure 13) in the report.-eric]

  13. 13

    Eric, Re#6 comment,

    Ok. I went back and reread page 13. Is Figure 3 top correctly captioned?

    If assessing model behavior over the short term is a silly idea, then why are there so many references on page 15 about 10 year trend values? Why not 8 or 9 year values? Knight et al. looked at trends from a short as 2 years! Apparently the reviewers didn’t reject that paper as being a “pointless, fruitless, silly exercise.” Why not?

    -Chip

  14. 14
    Chad says:

    The models actually track temperature trends since 2000 quite well (using Santer’s method of comparison). Redo the analysis starting with 2001 and you get different results. Just goes to show you that such analysis over a short period of time is not robust. I’ve got all the results up for those interested.

    http://treesfortheforest.wordpress.com/2009/09/26/ar4-model-hypothesis-tests/

  15. 15
    Tonyb says:

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

    Where? Please cite a reliable source.

  16. 16
    Steve Bloom says:

    The problem is that the possibility of a short-term large response from the GIS can’t yet be excluded.

  17. 17

    Chad, Re14:

    If models were getting things right (including weather noise), then the observed trends would be contained by the models at all time frames. That they are not, is a robust result that the models (or at least some of them) aren’t working right.

    -Chip

  18. 18
    Mark Gibb says:

    My problems with the AGW community do not involve the slow, methodological plodding of good science, it is the alarmism that is desired by politicians so they have the cover they need to empower themselves.

    I am reading the report now, so I cannot yet comment on the contents, but by first impressions, it looks to me that the “sky-is-falling” tone is the first thing someone sees when they look at the cover. The images look like they could have been taken right out of a disaster movie, complete with what looks to me to be a computer-rendered angry-ocean picture.

    Just giving the customers what they are after, I guess.

  19. 19
    dhogaza says:

    If models were getting things right (including weather noise), then the observed trends would be contained by the models at all time frames. That they are not, is a robust result that the models (or at least some of them) aren’t working right.

    This nonsense is the best denialist science can give us? Really? How disappointing.

  20. 20
    Eli Snyder says:

    Re: 7

    Sascha, would you mind providing a definition of “alarmist?” I’m not clear on exactly what you mean by that. You seem to indicate that it means saying that there is “imminent massive human tragedy,” which is not entirely clear either — but let’s take “imminent” to mean “within the next century” and “massive” to mean “affecting very large numbers of people” (say, more than a few million) and “tragedy” to mean “something that would severly adversely affect their lives”(for example, turning them into refugees). Those sound like reasonable definitions.

    In that case, even under conservative estimates (only 1 meter of sea level rise) we are facing “imminent massive human tragedy” just from sea level rise alone, and that’s only one of the many projected adverse effects even with relatively mild warming.

    If that’s the definition of “alarmist” then even the most conservative projections of what will happen on the current emissions path are “alarmist,” so it becomes a pretty meaningless term.

    Is there something else you mean by it?

  21. 21
    llewelly says:

    sascha says:
    24 November 2009 at 1:07 PM:

    Well, they do use the statement in the context of warning about mass “displacement” – a phrase that implicitly carries with it the connotations of “catastrophe” and “short time span” (as I stated before, it doesn’t make sense when looking at long time spans).

    “displacement” is a neutral term that is widely used for both slow and rapid movements. It does not imply connotations of “catastrophe” or “short time span”.

  22. 22
    tharanga says:

    On page 12, Canadell et al (2007) is cited as showing an increase in the fraction of CO2 that stays in the atmosphere, over the last 50 years. It is noted that there is a good deal of uncertainty in this estimate, due to interannual noise and uncertainty in the extent of land use changes.

    Since then, Knorr (GRL, 2009) has done his own analysis, attempting to account for uncertainty in the data, and saw no significant trend over that time period. I’m assuming the more recent paper was simply too recent to consider for mention in this report. Given the uncertainties involved, I don’t think the two papers are really all that much in contradiction to each other, but I am wondering if anybody here would like to comment on the methodologies in the two papers.

  23. 23

    I don’t need to read the whole report to comment.

    1) The summary entirely focuses on the negative which is unscientific. For example Antarctic sea ice is above IPCC forecasts. Just a small example I realize but one I am familiar with.
    [IPCC did not make a forecast of Antarctic sea ice. Nor is the recent increase in any way in contradiction to what the models show.

    2) The fact that the sea level comments are almost entirely reliant on Rahmstorf 2007, which published comments showed had serious flaws is an additional sign of trouble.

    There is little question about the solidity of the science around climate change, which I believe would stand on its own without resort to hyperbole. This type of unbalanced report doesn't serve the purpose that the author's intend.

    By now you must realize that for a majority of thinking people including the political class it is clear that we should drastically reduce the amount of CO2 being emitted. The problem is economic and political not scientific.

    [Response: Umm.. Yes, you do need to read the report. IPCC didn't project Antarctic sea ice, and there is nothing contradictory about what is happening, vs. what IPCC said about Antarctica. The question of Antarctic sea ice is well addressed in the report. Nor does this new report rely entirely on Rahmstorf; other studies are in excellent agreement with his. What specific 'flaws' are you alluding to?-eric]

  24. 24
    Bud says:

    @chip #13: I’m not an expert on the matter, but it seems fairly evident that whilst comparing a small (5-15 year) period with model projections over the same period is not terribly useful, comparing multiple 10 year (and, indeed, 2-3 year) trendlines across a longer-term period is a fairly common statistical technique. That’s certainly the difference between what you refer to as your own study and the work described on page 15 of the Copenhagen report.

  25. 25
    SecularAnimist says:

    I should be used to it by now, but the reaction from so-called “conservatives” always appears utterly bizarre to me:

    1. Science tells us that we have a very serious problem — indeed, a grave danger to the continuation of human civilization — from continued anthropogenic GHG emissions and consequent global warming and climate change.

    2. Some people propose solutions to this problem that are not to the liking of “conservatives”.

    3. “Conservatives” respond not by proposing solutions of their own that are more to their liking, but by denying that the problem exists.

    Now, why is that? Is “conservatism” incapable of proposing solutions, leaving “conservatives” no choice but to bury their heads in the sand and pretend there is no problem? Thereby rendering themselves irrelevant and impotent and leaving the field of solutions to those who propose the solutions that they dislike? Wouldn’t “conservatives” be better off acknowledging the scientific reality of the problem and getting a seat at the table where solutions are being debated?

  26. 26
    tharanga says:

    On page 13, the report mentions La Nina and the solar minimum in regards to 2008, and how the TSI was the lowest measured in the satellite record. While that solar minimum was lower than the other two solar minima, it’s not that much lower (expressed as a forcing) to be anything special, is it? Was that fact just tossed in there to tease the “it’s the sun!” crowd?

    Regarding how the solar cycle would show up in the temperature record: Fig 5 seems to take the solar cycle, convert it to an instantaneous forcing, and then further to an instantaneous temperature change. In an imaginary world with no other forcings and no ENSO, would the temperature history actually look like that in Fig 5, or would lagged response to the forcing smoothen out the variation?

  27. 27
    Chad says:

    Chip-
    If the models were absolutely perfect, they still wouldn’t generate trends that encompass observations consistently over every small time frame like the one I mentioned. The models are first spun up to equilibrium then various forcing histories and scenarios are imposed. Thus the internal variability of a perfect model and observations aren’t necessarily going to be in synchronization. This asynchronization could strongly alter trend analysis results over short periods of time. The fact that the analysis starting in Jan 2000 shows no significant difference doesn’t vindicate the models. Just look at the size of those error bars. It’s weather noise that’s undermining the power of the test. And the fact that the results change significantly when shifting the start year to 2001 shows the analysis is sensitive to the endpoints and not robust.

  28. 28
    Hank Roberts says:

    weblogplaza — the link behind “Nichols” –is a blogspam bot.

    [Response: thanks, deleted]

    > If models were getting things right
    >(including weather noise)

    Ah, yes, we should wait until we have much bigger and faster computers, and do nothing until we are able to model everything at the same time.

    “Delay is the deadliest form of denial.”

  29. 29
    sascha says:

    @ eric, regarding displacement caused by rise in sea level by 2100:

    Ever flown into Vancouver, BC? You’ll still be able to land at the Vancouver airport after 1 m of sea level rise …. if you have a seaplane.

    Well, coming from an engineering background, I must say that totally depends on how much the Vancouverians love there airport… (that is, how much they are willing to spend on constructional measures…) ;-)

    But I do get you point of course… I also realise it’ll be a much bigger problem for the poorer regions of the earth…

    @ dhogaza, regarding a possible implied “short time span” for drastic sea level rise:

    You’re right, when taking the article as a whole, it will be clear that “eventually” must in this sentence refer to timespans longer than 100 years. I did point this out in my original comment.

    It’s just that when I read that sentence in the report, I personally felt that in the specific context it was in (that specific chapter/page, rather than the whole book) it sounded rather alarmist (as opposed to unemotional, fair presentation of scientific knowledge).

    I don’t know, maybe I did misinterpret the language a litte. I am indeed a non-native speaker (btw, I’m honoured you guessed it primarily from my name rather than from my writing), and yes, like everyone else I am not exempt from personal prejudice.

    Part of my personal prejudice may be negative experiences with statements publicized by overzealous environmental groups regarding global warming and similar topics – statements which I naturally believed at first – turning out to be really not much more than the most catastrophic-sounding paragraph of a reputable scientific publication quoted out of context. I personally believe that even if it is for a commendable cause, exaggerating scientific results, or deliberately presenting them in a dishonest alarmist way is not acceptable.

    But I guess I should really stop spamming this comment space with my personal sensitivities and make way for the more scientific discussions by some of the commenters here…

  30. 30
    tharanga says:

    Re Pete, 12: So long as there is short-term variability in any data set, you can almost always try to claim that whichever variable (temperature, Arctic ice extent, whatever) is in “recovery”, so long as the most recent data point wasn’t the record high/low.

    But is there any value to making that claim? Is that really what you see, when you look at Fig 13?

  31. 31

    The heart of the matter is the following pasted from the subject report (I use quotation marks to separate the exact report words from my comments.):

    “Is the greenhouse effect already saturated, so that adding more CO2 makes no difference?”

    Yes, that is the question.

    “No, not even remotely. It isn’t even saturated on the runaway greenhouse planet Venus, with its atmosphere made up of
    96% CO2 and a surface temperature of 467 °C, hotter even than Mercury (Weart and Pierrehumbert 2007).”

    Huh? Who the heck cares about Venus?

    “The reason is simple:”

    Sure it is (sarcasm drips from screen). Continue reading to see how a simple person comprehends this, thus demonstrating that it is not simple.

    “the air gets ever thinner when we go up higher in the atmosphere. Heat radiation escaping into space mostly occurs
    higher up in the atmosphere, not at the surface – on average from an altitude of about 5.5 km. It is here that adding more
    CO2 does make a difference. When we add more CO2, the layer near the surface where the CO2 effect is largely saturated
    gets thicker – one can visualize this as a layer of fog, visible only in the infrared. When this “fog layer” gets thicker, radiation
    can only escape to space from higher up in the atmosphere, and the radiative equilibrium temperature of -18 °C therefore
    also occurs higher up.”

    OK! But maybe a little more about the importance of the -18 deg C would be helpful.

    “That upward shift heats the surface, because temperature increases by 6.5 °C per kilometer as one goes down through the atmosphere due to the pressure increase.”

    Maybe the 6.5 deg C per kM is so, but not due to pressure increase. You can’t be serious that pV=nRT applies after millions of years of adjusting.

    “Thus, adding 1 km to the “CO2 fog layer” that envelopes
    our Earth will heat the surface climate by about 6.5 °C.”

    No, that layer will perhaps force the earth to be warmer in order to establish the -18 deg C through the fog layer. I can see that the earth surface needs to be more than the temperature of the lower most layer in order to get a net radiative heat transfer outward. I guess that rule would apply through successive infinitessimally thin layers all the way up to the final -18 deg C layer. So now if the earth gets 1 deg C warmer there should be significant heat transfer to the -18 deg C layer, and of course it would warm that layer causing higher rate of heat release. Since there is a 6.5 deg C difference, as that heat is released to bring things back to equilibrium, the earth surface would be returned to its original temperature.

    It looks to this simple folk (namely me) like there is something wrong here.

    [Response: I'll readily agree that the analogy in the report is a bit difficult to follow. However, it can't be so bad, as you seem to have understood the essential points. Your key misconception is encapsulated in your last sentence -- the surface temperature *does* return to equilibrium, but not to its original value. Adding more greenhouse gases means the equilibrium has changed -- the stratosphere cools (as has been observed), and the surface warms (as observed)-- until that new equilibrium (warmer surface, colder stratosphere) is reached.--eric]

  32. 32
    MapleLeaf says:

    Have read the report. There is an incredible amount of science in there! What really stood out for me, in addition to the inclusion of more and more observational data sets, is that the IPCC projections of sea level and Arctic sea ice minima have been way too conservative. So much for IPCC “alarmism”. It seems the biosphere is going to alarm us if anything in its rapid response to the anthro forcing. Given the third lowest minimum this past summer, and very slow growth of the ice in October and November, the stage has been set for yet another record low Arctic sea ice extent late next summer.
    Of course those in denial and the contrarians, who feel it necessary to point out every flaw, perceived or real, will nitpick their way through this, as they always do. I guess it would be too much to request that we keep our critique constructive and try and focus on the much more important big picture here?
    A last point, if some of the wording may seem ‘strong’, like it or not that is what is needed to mobilize people. Many, many people have fallen victim to the rumours that the warming has stopped, slowed or even reversed the last 10 years. This has given people a false sense of security. That said, the policy makers and politicians do finally seem to be showing a sense of urgency (except Canada of course, my apologies to everyone on our behalf for showing no leadership at all on this file).

    PS: Why were Swanson et al. (2009) and Murphy et al. (2009) not included? They would have really strengthened the report.

  33. 33

    Bud (re#24),

    In fact, in my work (currently under peer-review), I do precisely as you describe that I should–not as you describe what you think I did. In my comment #6 I wrote that I am working “on trying to properly compare observed global temperature trends during the past 5-15 years with model projections during similarly short periods.” Note “properly” compare and during “similarly” short periods–in fact, I am comparing observed trends with the full range of trends derivable from all climate models for all periods of a particular length (5 to 15 years) projected during the first 20 years of the 21st century under the SRES A1B scenario (one which according to the Copenhagen Diagnosis underestimates the emissions which have taken place—so my test should be on the conservative side). It would be difficult to do a more thorough test that the one I am performing.

    I employ a technique similar, but more widely applied and better constrained, than either Easterling and Wehner (GRL 2009) or Knight et al. (BAMS 2009) both of which also compared short-period observed trends with short period model projections. Since both were published in the literature, I assume that not everyone thinks the task pointless.

    -Chip

  34. 34
    Don S says:

    sascha says:
    @ eric, regarding displacement caused by rise in sea level by 2100:

    Ever flown into Vancouver, BC? You’ll still be able to land at the Vancouver airport after 1 m of sea level rise …. if you have a seaplane.

    Well, coming from an engineering background, I must say that totally depends on how much the Vancouverians love there airport… (that is, how much they are willing to spend on constructional measures…)
    ——-
    The entire Schiphol Airport in Amsterdam is below sea level. The runways are 10′ or so below sea level. If there is sufficient financial incentive Vancouver will figure it out.

    [Response: That's the point. There are *costs* associated with global warming.--eric]

  35. 35
    SecularAnimist says:

    sascha, regarding your comments (e.g. #7 and thereafter) about what you seem to feel is “alarmist” ambiguity & vagueness in the report’s assessment of potential sea level rise, here is what the Executive Summary has to say:

    Sea-level prediction revised: By 2100, global sea-level is likely to rise at least twice as much as projected by Working Group 1 of the IPCC AR4, for unmitigated emissions it may well exceed 1 meter. The upper limit has been estimated as – 2 meters sea-level rise by 2100. Sea-level will continue to rise for centuries after global temperature have been stabilized and several meters of sea level rise must be expected over the next few centuries.

    I think that language makes it very clear what time frames the report is talking about for “several meters” of sea level rise.

    Personally I am not too “alarmed” about sea level rise because by the time the Vancouver airport is under water, I expect that human civilization will have long since succumbed to world-wide famine resulting from a global failure of agriculture resulting from prolonged, intense, widespread continent-wide mega-droughts — not to mention the disappearance of fresh water supplies for billions of people.

  36. 36

    Chad (re# 27),

    Right, sorry, I misunderstood. Comparing observed trends over a particular calendar period with model projected trends during the same calendar period, during short timescales is not a robust comparison–too much weather noise.

    That’s why I do my comparisons using the complete distribution of trends derived from all similarly lengthed periods during the first 2 decades of the model projections for the 21st century–a period of relatively stationary projected change–and one that should be similar to recent observed years.

    -Chip

  37. 37
    GPB says:

    “[Response: That's the point. There are *costs* associated with global warming.--eric]”

    But there are also benefits. Longer growing season, more arable land, and lower heating bills :-)

    [Response: What you are implying is that "The costs of doing something about global warming are greater than the benefits of doing nothing." Evidence, please? (Oh, and *where* do you get the idea that there will be more arable land?!)--eric]

  38. 38
    viento says:

    Why is the paper by Siddal, Stocker and Clark published in Nature Geosciences 2009, which indicates a sea-level rise in the range of 7-82 cm, and therefore clearly different from Rahmstorf 2007, not even cited?

    [Response: For some perspective on that, see Stefan's discussion of that paper, here. -eric]

  39. 39
    Mark A. York says:

    RE: 15, “Where? Please cite a reliable source.”

    Meet Jason-1 and Grace at your service.

    http://climate.nasa.gov/keyIndicators/

  40. 40
    dhogaza says:

    I don’t know, maybe I did misinterpret the language a litte. I am indeed a non-native speaker (btw, I’m honoured you guessed it primarily from my name rather than from my writing) …

    You write just fine in my language, except for the english rather than american spelling :)

    Part of my personal prejudice may be negative experiences with statements publicized by overzealous environmental groups regarding global warming and similar topics – statements which I naturally believed at first – turning out to be really not much more than the most catastrophic-sounding paragraph of a reputable scientific publication quoted out of context…

    I don’t think anyone would deny that this happens at times …

  41. 41

    You can visually see what 1 to 2 meters of sea level rise would look like for hundreds of cities and towns along the east, west and gulf coast at: http://www.architecture2030.org/current_situation/cutting_edge.html

  42. 42
    JonJermey says:

    “The entire Schiphol Airport in Amsterdam is below sea level. The runways are 10′ or so below sea level. If there is sufficient financial incentive Vancouver will figure it out.

    [Response: That's the point. There are *costs* associated with global warming.--eric]”

    Well, you have just changed your tack. First you say that it will be a disaster because of flooding; now you want to say that it will be a disaster because of the costs of flood mitigation. But cutting emissions also has costs: and it’s not at all clear to me — even assuming the sea-level rise data is more reliable than another data set has recently been shown to be — that the cost of building a 1m seawall is greater than the cost of cutting emissions. The first is a routine engineering operation that people do all the time and have been doing for centuries. The second requires a radical and drastic change in the way civilisation operates. If your reason for saying “We should do A rather than B.” is because B costs less, it’s not enough to merely assert that: you have to show it.

    [Response: Actually *I* don’t need to show anything. There is a huge literature on this already. Read it. You might start with the Stern report.

  43. 43
    Stuart says:

    Can someone answer why CO2 is considered a pollutant? According to the graph at this link:
    http://www.barrettbellamyclimate.com/page24.htm
    which is formulated from the MODTRAN program, the widely proph­esied doubling in CO2 concentration from the pre-industrial value of 285 ppmv to 570 ppmv would be associated with an increase of just 1·5°C.
    This data takes into account the full path length of the atmosphere as well as broadening of the CO2 absorption bands.

    [Response: 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]

  44. 44
    Mark A. York says:

    Lee Fu’s presentation on sea level at the JPL Climate Symposium is good. He also cites the Rahmstorf paper.

    http://climate.nasa.gov/ClimateSymposium/

    Up 20 cm (8 inches) since 1920.

  45. 45
    Llama Cheese says:

    Bravo!
    This is excellently done! Seriously, whoever designed this is a freaking genius. Just in time to fight the denialists. Nobody can truly read this and walk away unconvinced of the need for action.

  46. 46
    Ryan O says:

    This is for Eric Steig:

    I think you may have made an error in your response to #31. The cooling of the stratosphere is a transient, not equilibrium, condition. In the simplest example, let us assume solar output remains the same and neglect the any change in concentration of GHGs in the stratosphere.

    With these conditions, a stepwise increase in GHGs causes a temporary reduction in outgoing radiation through the stratosphere. As the stratosphere is warmed by both incoming solar radiation and outgoing re-radiation from the surface of the earth, the reduction in outgoing radiation results in stratospheric cooling.

    As the surface temperature of the earth increases, however, the outgoing radiation also increases, and stratospheric temperature begins to recover. At equilibrium, the outgoing radiation will be the same as what it was prior to the stepwise change and the stratosphere returns to (approximately) the same temperature prior to the perturbation.

    The reason the cooling stratosphere is an important characteristic of GHG warming is because GHG concentrations are continually rising (in contrast to the step change example) and, therefore, equilibrium is never reached. Even in this case, though, a cooling stratosphere does not necessarily follow for all conditions. Because stratospheric temperatures will eventually begin to recover as the troposphere approaches equilibrium, the stratosphere can warm even under conditions of increasing GHG concentrations if the rate of the GHG increase is reduced sufficiently.

  47. 47
    Timothy Chase says:

    Mark A. York wrote in 39:

    RE: 15, “Where? Please cite a reliable source.”

    Meet Jason-1 and Grace at your service.

    http://climate.nasa.gov/keyIndicators/

    Mark, I had been wondering what was going on with the current El Nino. Your link provides the following when you look at the current sea-level data:

    November 12, 2009

    El Niño is experiencing a late-fall resurgence. Recent sea-level height data from the NASA/European Ocean Surface Topography Mission/Jason-2 oceanography satellite show that a large-scale, sustained weakening of trade winds in the western and central equatorial Pacific during October has triggered a strong, eastward-moving wave of warm water, known as a Kelvin wave. In the central and eastern equatorial Pacific, this warm wave appears as the large area of higher-than-normal sea surface heights (warmer-than-normal sea surface temperatures) between 170 degrees east and 100 degrees west longitude. A series of similar, weaker events that began in June 2009 initially triggered and has sustained the present El Niño condition.

    El Nino Picking Up Steam
    http://www.jpl.nasa.gov/news/features.cfm?feature=2358

    There are links to some great resources, e.g., satellite images and data from Jason, Grace, Terra, QuikSat, AIRS and MLS along the right hand side, at least some of which contain links to entire websites that are devoted to the specific satellites and the images and data obtained from them.

    Definitely worth bookmarking.

  48. 48
    Axel Edgren says:

    @ Mark Gibb

    “My problems with the AGW community do not involve the slow, methodological plodding of good science, it is the alarmism that is desired by politicians so they have the cover they need to empower themselves.”

    Politicians! In general! They will kill us all!

    Nothing alarmist about your worries, Mark…

  49. 49
    Chris S. says:

    #37 GPB

    Whilst growing season may be extended beyond the summer months into autumn, warmer, wetter, winters are likely to mean that spring sowing won’t get much earlier (as the ground will be too sodden). Crop pests and disease vectors however (e.g. aphids) show a strong relationship to winter temperature (particularly Jan-Feb) and are expected to arrive in crops (in higher numbers) at an earlier – more susceptible – growth stage.

  50. 50
    Hank Roberts says:

    > *where* do you get the idea that there will be
    > more arable land?!)

    We’ve seen this error before:
    http://tamino.wordpress.com/2007/12/16/wiggles/#comment-10862

    See also ‘Mercator’ in this nonsense:
    canadafreepress.com/2006/harris061206.htm


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