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Comments 109251 to 109300:

  1. Philippe Chantreau at 03:21 AM on 25 September 2010
    Video update on Arctic sea ice in 2010
    Cryosphere today is showing even more evidence of how warming has stopped and how sea ice is doing a spectacular recovery: Arctic sea ice area appears to have bottomed very close to 3 million sq. km, on par with 2008, pretty close to the all time low of 2007 and significantly lower than last year. Lowest sea ice anomaly so far this year was reached in June, when a strong Arctic dipole led to the fastest melt ever recorded at that period, a similar rate to that of August in the all time low 2007. That month in 2007 also had a strong dipole situation. This year's lowest anomaly may not have been reached yet, depending how fast the ice is going to form. Meanwhile, something funny is happening to Antarctic sea ice. After a strong positive anomaly early in the season, it is now showing over 700k sq. km below baseline, a rather unusual occurrence at the time when it should peak. If the data are correct, that brings the global sea ice around 2.5 million sq. km below the 1979-2008 average, close to 2007, on par with 2008, much lower than 2009. Some recovery.
  2. A detailed look at Hansen's 1988 projections
    angusmac, I'll try one more time to explain to you. The temperature change is based primarily on 2 factors, radiative forcing (which depends heavily on emissions scenarios) and climate sensitivity (which is a product of the climate model). Regarding the first factor, Scenario B has been quite close to reality. There is no point in comparing to Scenario C, which has not. It doesn't matter if the temps follow closer to C, because the real-world emissions do not. Since the real-world emissions and forcing have been close to B, we can then examine the second factor - climate sensitivity. As I showed in the article, we can then determine that the real-world sensitivity has been around 3.4°C for 2xCO2. Notice my use of the term "real-world". You're obsesing with Scenario C, which is a hypothetical world which does not match the real world. Both of the factors mentioned above are incorrect in Scenario C. One is too high and one is too low. The problem is that in Scenario C, the forcing flattens out, whereas that will not happen in reality. There is simply no chance that Scenario C will continue close to reality because it does not reflect real-world emissions or radiative forcings.
  3. The Big Picture (2010 version)
    cruzn246 #7 - I suggest you actually click the links and learn something. There's a pretty darn big difference between scientific evidence and "pure speculation." bverheggen #9 - valid point, I may add a bit on aerosols. I wrote a rebuttal on the subject recently which I didn't link in this article. Dan Olner #11 - there's a difference between what it would take for AGW to be wrong (our understanding of physics would have to be wrong) and what it would take to disprove AGW. To disprove the theory, just demonstrate that the planet is not warming or climate is not changing as it predicts. I recommend you click the 'fingerprints' link in the article to see what I mean. Ken Lambert #24 - perhaps you're unfamiliar with Skeptical Science. The purpose of the site is to debunk false skeptic arguments with scientific evidence. paulm #25 - I'll consider rewording the conclusion a bit.
  4. Urban Heat Islands: serious problem or holiday destination for skeptics?
    As a postscript, I'm happy to discuss this all further, but I'll be leaving town shortly for the weekend and may not be revisiting the site much if at all before Monday.
  5. The Big Picture (2010 version)
    Following from PaulM's comment, this is a useful article: The Psychology of Global Warming (AMS, full text pdf) Leaving aside that little group tagged by Leiserowitz as the "dismissive," if we take heed of what we've learned of how people think, our communications actually can be made more effective, more robust in the face of industrial PR.
  6. A detailed look at Hansen's 1988 projections
    RE: comments from myself, kdkd, and BP above: It's off-topic for this thread, but I've just posted a lengthy "reanalysis and commentary" over in the appropriate thread (Urban Heat Islands: serious problem or holiday destination for skeptics?).
  7. Urban Heat Islands: serious problem or holiday destination for skeptics?
    Since BP's analysis on the first page of this thread has become the subject of discussion elsewhere, I thought I'd revisit it briefly. Recall that BP picked 270 GHCN stations, calculated their temperature trend over the decade 1990-2000, and then calculated their change in population density over the same period from GPWv3. He then created a model relating temperature trend to the number of doublings of population density. His claim was that the Y-intercept of this model showed that a hypothetical station located at a site with no change in population density would have a trend of +1.5C/century over that decade. For context, note that a bunch of different reconstructions using land stations only show an actual trend of +2.25C/century over the same time period. Thus, BP's results, if you grant all the various assumptions underlying his analysis and assume that his hand-picked stations were representative of all land stations, would suggest that UHI explained about 1/3 of the observed temperature increase over land and about 10-12% of the global increase. Commenter kdkd and others have questioned the statistical significance of that model. Since BP hasn't been able to explain that, I've tried to sort-of replicate it. Of course, without knowing what stations he used it's not possible to replicate his analysis exactly, and for a number of reasons (to be explained below) I don't think it's worth going through all the work of fully replicating it even if we did know what stations he used. Instead, I took the short-cut of just digitizing the points on the graph from his comment, and re-doing the regression analysis. Unfortunately, the graphic is noisy and it's not possible to identify all 270 points. I got 204 of them, but for the rest I'm just not confident in my ability to correctly identify them in the noise. Using those 204 points gives a model with an r2 of 0.075, meaning it explains very little of the variance within the data. (This is not surprising given the spread among the points in the graph). The estimate for the intercept is 1.4C/century, just a hair below BP's calculation of 1.5. The 95% confidence interval around this estimate is approximately 0C/century to 3.0C/century. In other words, UHI could explain all the observed warming over land, or at the opposite extreme it could be artificially cooling the data, actually reducing the land surface trend from its "true" value of 3.0C/century to the observed 2.25C/century. Of course, neither of those extremes seems likely. Given that the land is presumably warming faster than the ocean (heat capacity), UHI can't realistically explain most or all of the observed warming over land. Likewise, I don't think anyone seriously suggests that overall, globally, UHI would be negative. So my admittedly crude attempt to replicate BP's analysis suggests that his model is not very informative, since it fails to exclude what are almost certainly unrealistic values at both the high and low extremes. That's OK, it's still interesting (though probably not publishable....) As I've mentioned earlier in this thread and elsewhere, there are serious concerns/problems with BP's analysis that probably make it non-worthwhile to pursue it much further. First, the quality of the locational information in the GHCN metadata is known to be poor, and the spatial resolution of the GPW population density data is clearly insufficient to provide estimates of local population density at individual stations. Second, one decade is a very short time to be looking at trends in both temperature and population density. Third, we don't have any reason to believe that BP's hand-picked 270 stations are representative of the overall land surface, and in fact there are good indications that they are not (according to BP's original comment their mean trend differs substantially from the observed land surface trend based on various reconstructions). This is not to suggest that BP deliberately picked unrepresentative stations -- it's just difficult to get a representative sample without using somewhat sophisticated methods. It's worth noting that there's no a priori reason to expect that the real world would actually conform to this model, particularly when extrapolated to low population densities. On the contrary, it seems physically improbable. It's also worth noting that we have reliable and well-validated satellite measurements of sea surface temperature trends which show clear warming during this period. Given that there are good physical reasons to expect warming over the ocean to lag warming over land, the global SST trend would seem to limit how much land warming could be explained by UHI (if your claims for UHI would bring the land trend below the ocean trend, you've probably made a mistake somewhere). If you dealt with the first three objections, and found that the resulting model actually explained a large proportion of the variance in the observed data, it would definitely be worth pursuing this. What we have right now, though, is an analysis that is crippled by those three objections and only yields an r2 of around 0.075, and fails to rule out more or less impossible answers at both extremes. Bottom line, BP's analysis doesn't really do anything to support the claim that UHI explains as much as 10% to 12% of the observed global temperature increase. The true value is probably in the low single digits. Apologies for the length of this comment.
  8. A detailed look at Hansen's 1988 projections
    angusmac @112 Scenarios A, B and C all represent the same "black box" - just with a different input value; the CO2 emissions for future years (his future, our past). Scenarios A B and C could be said (perhaps somewhat crudely) to correspond to predictions of different CO2 concentrations in the atmosphere in the future. Since we are now in Hansens future, we can look at the current actual CO2 concentration in the atmosphere and determine that emissions have most closely followed Hansens scenario B. Thus scenario C (and A) is irrelevant because it was a prediction for a course of action the world did not take
  9. Climate scientists respond to Monckton's misinformation
    Roger... I believe solitary corals developed in the Cambrian but reef forming corals came about in the early Ordovician.
  10. Does Climate Change Really Matter?
    @ianw01: that's why it's always safer to say that an increase in extreme weather events is "consistent" with AGW theory.
  11. A detailed look at Hansen's 1988 projections
    @angusmac: Scenario C is not relevant because it is based on CO2 emmissions that do not accurately represent actual, real-world emmissions. Scenario B, however, uses figures that are close to real-world emmissions, and thus offer the same basic parameters (except for climate sensitivity). The fact that Scenario C is closer is irrelevant, because it uses does not use real-world emmission values. Do you understand your mistake?
  12. The Big Picture (2010 version)
    A good paper on why a large portions of the general public, journalists, and policy makers dont get the "...scale of the problem and the urgency of required action" is : What psychology can teach us about our response to climate change http://www.guardian.co.uk/environment/blog/2010/sep/23/climate-change-psychology-response-scepticism "Simply presenting the facts and figures about global warming has failed to convince large portions of the general public, journalists, and policy makers about the scale of the problem and the urgency of required action. From a psychologist's perspective this disconnect is not surprising."
  13. The Big Picture (2010 version)
    Re: Ken Lambert (24)
    "What is it with something about 'she who is without sin casting the first stone?'"
    Actually, it's "If any one of you is without sin, let him be the first to throw a stone at her." Remember, the society of the day was patriarchal, so the gender of the expression is male. (but perhaps you were adapting it to adelady?)
    "Presumably in your view only deniers and sceptics (why not call them tanks?) have the same old talking points."
    Those same old talking points you reference are the ones whose science the "deniers and sceptics" fail time and again to overcome.
    "As if the age of a point has anything to do with its value."
     Well-spoken, sir. The Yooper
  14. The Big Picture (2010 version)
    Nice post. I have to add that I think the conclusion can be tightened up a bit. We may not know the exact risk but we have a pretty good idea what the ballpark figures are in terms of risk management. It's not difficult when we can clearly see that continued AGG emissions will more than likely result in extreme GW, which will most likely result in a severe mass extinction event. It clearly will most likely result in to collapse of modern civilization and very probably the reduction of the human species to very low numbers. There is also a possibility of the run away GH effect which would annihilate life. So the statement "uncertainty regarding the magnitude of the risk" in the conclusion is a bit miss leading.
  15. The Big Picture (2010 version)
    Adelady #8 "It's not the writers who are reinventing the wheel, it's the conversational, opinionated know-nothings who revive and recycle the same old talking points." What is it with something about 'she who is without sin casting the first stone?' Presumably in your view only deniers and sceptics (why not call them tanks?) have the same old talking points. As if the age of a point has anything to do with its value. Old talking points arise because they might be uncertain, difficult, controversial and not resolved - like the real contribution of CO2GHG to warming, WV and CO2 interaction, OHC measurement, etc etc. BTW who is dana1981 anyway - he/she seems to be recycling lots of 'old talking points' lately.
  16. The Big Picture (2010 version)
    If there is a single ongoing experiment offering the best hope of crisply falsifying the notion of anthropogenic climate change, perhaps it's night time surface atmospheric temperatures? This is sampled with ancient, thoroughly understood instrumentation, comprehensively deployed, no confounding factors if the simplest and most transparent data conditioning is permitted. A reasonable person might conclude that if night time temperatures were refusing to behave "properly," we may have a wee problem with the notion of AGW. As it stands, overnight temperatures are behaving exactly as we'd expect; the behavioral details of the decline of diurnal surface temperature variation seem impossible to explain by other means. Perhaps it's the very simplicity of this message of surface temperature records which compels "skeptics" to discard surface temperature records as false. Failing a scientific explanation, speculations about fraud or incompetence are all that's left to discount the first, easiest, most bulky and unequivocal evidence of AGW. Ironically, past such simple matters as diurnal temperatures, "skeptics" seem to be becoming lost in the myriad of complicated knock-on findings of researchers delving into climate change. The more evidence they demand, the less perfectly atomic and hermetic new evidence will be; ignoring the obvious means dealing with the arcane. Huntjanin, for my part I don't think any but the very softest and least committed "skeptic" will be swayed by -any- argument based on science. This "debate" is not really about science at all. For helping ordinary people who are curious about this matter and want to know what all the fuss is about, offering simplified explanations with pointers to details seems a worthwhile exercise. Constructing these basic explanations is a fascinating exercise in itself, a matter of teasing essential concepts out of things often very complicated.
  17. Does Climate Change Really Matter?
    Thanks, John, for the reply regarding data supporting extreme weather. The link and references therein were helpful. But still, we must be careful about attributing too many weather events to global warming, without solid evidence. In my view it is one of the weakest aspects of the "alarmist" positions.
  18. The Big Picture (2010 version)
    @Dan Older, #11, Excursions in to the philosophy are usually considered OT, but here is my 2c. "Falsifiability" is a good criterion to demarcate science from non-science. In that respect, it resembles Occam's Razor or Hume's Fork. However, it is not a good criterion to assess a branch of science, as climate science has become. Scientific theories are usually composite and stated as generally as possible. A black swan may falsify the simple hypothesis "All swans or white" but not the more general hypothesis "Most swans are white" or even "Some swans are white". With inductive logic, it is often easier to modify the hypothesis than reject it. The difficulty of "falsifying" a science is best illustrated by a story from physics. At the start of the 19th century, astronomers found that the planet Uranus was not appearing as predicted by Newton's Laws. Did they therefore stop using Newton's Laws? Of course not - the laws were too accurate in other places to drop them completely. Instead, two astronomers (Adams and Leverrrier) used the discrepancies to propose that there was another planet beyond Uranus. There prediction was verified when the planet Neptune was observed in 1846, exactly where it was predicted to be. Fine, a triumph of science. Bur later in the century discrepancies were found in the orbit of Mercury, and again the existence of another planet was proposed (called Vulcan). But Vulcan was never observed, and the discrepancy was later correctly explained by Einstein's Theory of Relativity. However, in the interim, Newton's Laws had continued to be used with gusto. So "falsifiability" is too simple a criterion to judge a large and expansive scientific programme. It may work when a science is in its infancy - the best example I can think of is Fred Hoyle's Steady State Theory of the cosmos, which was slain by the simple observation of the microwave remnants of the Big Bang. But the Big Bang theory iteslf is now so complex and composite it is doubtful if a single observation could dethrone it overnight. The reference you gave was somewhat confused - it referred to a science discussion in 1961 as if it had contemporary relevance, and provided no instances where climate scientists were making predictions that were not falsifiable. I find deniers take simple lacunae in the theory of AGW and immediately jump up and down saying "Falsified! Falsified!". PS Just read Michael Searcy's comment #20... Dr Schneider states it much more succinctly than me!
  19. The Big Picture (2010 version)
    First i want to say this is an excellent post. @huntjanin... When i am arguing with someone about AGW I am not focused on convincing them as they are usually too invested in their denial. What I try to keep in mind is the possible audience that is listening to or reading the comments. Those are the ones I am trying to inform by offering civil, reasoned, and fact based replies. I have used this site as a resource for some time now. The primary reason is to better educate myself which with this 50+ year old brain is a struggle at times. High school and college science was a very long time ago. Thanks to John and all the contributors who devote so much time and energy to keeping this a much needed model of civil discourse and learning.
  20. A detailed look at Hansen's 1988 projections
    Dana#85 Scenario C is not irrelevant. On the contrary, it is relevant because it matches actual temperatures better than the other scenarios. It may help to think of Scenario C as a “black box” that gets the right answers. I enclose Figure 2 as explanation (click here for a high resolution image). Figure 2: Scenarios B and C Compared with Measured GISS LOTI Data (after Hansen, 2006) It should be noted that the emissions in Scenarios B and C are similar until 2000. Thereafter they diverge. Scenario C emissions are curtailed at their 2000 level whist Scenario B emissions continue to increase. Dana has shown that the Scenario B emissions are quite close to reality. Nevertheless, the following points are evident from Figure 2:
    1. Scenario C provides a better prediction of real temperatures than Scenario B.
    2. The Scenario C warming trend for 1984-2009 is 0.24 °C/dec. This is near to the measured rate of 0.19 °C/dec and is significantly closer to reality than the Scenario B rate of 0.26 °C/dec.
    3. The Scenario C prediction for 2000-2019 is nearly zero at 0.01 °C/dec. Furthermore, for the ten years that have elapsed since 2000, it appears to be “on the money.”
    CONCLUSIONS Hansen and his 1988 team are to be commended for producing models that are close to reality. Scenario C in particular has shown significant skill in predicting actual temperatures. Additionally, Hansen’s (2006) comments on the 1988 models that,“… a 17-year period is too brief for precise assessment of model predictions, but distinction among scenarios [B & C] and comparison with the real world will become clearer within a decade [2015].” I concur, let us wait until 2015 to see which scenario is correct. Will the “black box" that is Scenario C be right or will the real world move closer to Scenario B?
  21. The Big Picture (2010 version)
    Dr. Schneider does a great job addressing the falsifiability of climate science in a lecture he gave back in February which has been given the title, "Climate Change: Is the Science 'Settled'?" In summary he states...
    "Climate system science, like others, is really a preponderance of evidence based outcome. It is not falsifiable. Not in the short run....We do not falsify by single experiments. We falsify on the basis of accumulated numbers of papers and number of bits of information."
  22. The Big Picture (2010 version)
    huntjanin: "My doubts about the wisdom of this project will of course vanish immediately if someone can assure me that one or more of these basic posts has had some positive effect on a denier." Related to that, just been watching the late Steve Schneider tackle a room of sceptics. It's a fantastic insight into a range of sceptic mindsets that you just can't get from the interwebs. A number of them clearly have the wherewithall - given the right information and time - to piece together the story. They've just been exposed to some misleading information. But one or two - the doctor near the start - ask Schneider for an explanation on something, get a really clear explanation, and then repeatedly shout him down saying he hasn't answered the question. The heartening thing seems to be, he's the rarity, not the norm. The question then is, what's the ratio of rational to irrational on the web? And are people that come here a self-selecting audience? Oh - here's a link to the video. Clearly, it wasn't hard to gather a doubting audience in one place, willing to listen to a prominent scientist. I suspect blog science suffers far more from ghettoisation. Maybe the answer is that skepticalscience.com and other sites are needed, but until the information here gets out into meatworld public forums, its impact may be lessened.
  23. A detailed look at Hansen's 1988 projections
    BP writes: What about doing some work yourself? I have shown you the data sources used (SEDAC/GPWv3 and GHCNv2) and also described the basic method, enough for a hint. The link in BP's post is to this comment. In the immediately following comment I showed that even granting all your assumptions, the UHI effect would explain around 6% to 9% of recent observed warming over land, and around 3% globally. The analysis that kdkd has been repeatedly challenging you on was described in this other comment. Unfortunately, it is not replicable by anyone else, because you wrote in the very first sentence "I have selected 270 GHCN stations worldwide with a reasonably uniform distribution over land [...]" without identifying the specific stations. In that comment, you wrote: But the most important finding is that there is a (not very strong) correlation between these two parameters, so a regression line can be computed. What kdkd has been bugging you about is simply the statistical significance (or lack thereof) of that regression. You said it was "the most important finding". You also stated that the correlation was "not very strong", so it's understandable why kdkd would assume that you'd looked at the statistics for your model. If you had saved the results of that analysis, it would be exceptionally simple to just post the F-test result or 95% confidence interval or whatever. Thus, my assumption is that you probably did the analysis in a hurry, wrote up that comment, and then didn't bother saving it. Personally, I don't see this as a really big deal. My thoughts on BP's analysis were given here and here. My guess is that: (1) The significance of BP's model was probably very low (low enough to make it all meaningless). (2) The hand-picked set of stations seems to be very unrepresentative of the overall population of land stations, as I noted in the linked comments. I don't mean to suggest that this was deliberate, just that it's hard to get a representative sample. (3) I don't think the quality of either the coordinate information in the GHCN metadata or the spatial resolution of the population density data are sufficient to actually support the type of analysis described. Thus, I was and am still skeptical.
  24. The Big Picture (2010 version)
    huntjanin: Dont' just think about turning deniers. Also think about preventing soft "believers" (yuck) from turning.
  25. The Big Picture (2010 version)
    Thanks, Adelady, for your good comment (#8). My doubts about the wisdom of this project will of course vanish immediately if someone can assure me that one or more of these basic posts has had some positive effect on a denier.
  26. A detailed look at Hansen's 1988 projections
    BP: By the way, I think you'll find that I'm extremely familiar with the open source development model. I endorse it and support it for a number of uses, and argue for its use wherever possible with my colleagues, frequently quite vigorously. I'm also familiar with the problems surrounding scientific computing and the issues which cause a divergence from more traditional allegedly more rigorous software engineering practices. I am just finishing the reviews for a paper I wrote that argues strongly for the use of an open source model, and revision control protocols (using git for what it's worth) in social science research which will hopefully be published in the Australasian Journal of Information Systems next year. Anyway this is becoming increasingly off topic. Take home message: put up, or continue to have your credentials and motivations questioned.
  27. The Big Picture (2010 version)
    Sorry Dan, I mouthed off without reading your post properly, and instead made that assumption based on Alexandre's response. I see that you are not in fact making the assertion that AGW theory is not falsifiable.
  28. The Big Picture (2010 version)
    Hey John, Dan Olner's assertion that greenhouse gas induced warming is not a falsifiable theory and therefore not science is a 'skeptic' argument for which you don't have a refutation! I've seen it used a few times here and there, so perhaps it needs one. Engage your brain Dan. I'm sure you can think of a few ways to falsify AGW theory if you try. For example if any of the phenomenon in John's Ten fingerprints of global warming post were not observed to be occurring, then that would constitute evidence that something was amiss with the theory.
  29. A detailed look at Hansen's 1988 projections
    BP #108. That's a very long winded attempt at justifying why you won't give me the raw data that you used to make the graph you presented. I want this so that I can assess the validity of your claim statistically. It's not possible to do so without it. Just do it, I'll report back and then we can let it go. I don't intend to let it go otherwise, and it should be a simple job for you to release the data as it was processed by you. Your attempt at justifying why you won't do so is very poor. Isn't this the very kind of defensive behaviour that you claim is unacceptable among the professional climate scientists?
  30. A detailed look at Hansen's 1988 projections
    #107 kdkd at 14:20 PM on 24 September, 2010 My own accusation of BP's possible engagement in scientific dishonesty or incompetence is based on data he's presented on this site. He could make the problem magically go away if he just responded to the problem Your perception of a "problem" is rather odd. I thought we are here to learn and understand what's going on in climate science, not to make our egos fatter. Therefore if you keep accusing me of engagement in scientific dishonesty or incompetence or even scientific fraud it is your problem, not mine. And it would not go away, magically or otherwise, no matter if I took up the gauntlet or not. What about doing some work yourself? I have shown you the data sources used (SEDAC/GPWv3 and GHCNv2) and also described the basic method, enough for a hint. Rest assured I know how to use and abuse statistical tests, but the thing is statistics is worthless in establishing facts until the underlying processes are understood properly. For example I have just realized the easy-to-understand tidbit there is a hysteresis between local population density and UHI effect. That is, increasing density has a more or less immediate warming effect while decreasing density shows up in a delayed manner (man made structures do not go away immediately as people move out). It is not lack of statistics that makes an argument unscientific but mistreatment of concepts. So, if you are not willing to work, at least please stop whining. As I have shown you a sizable UHI effect is almost inevitable in the surface temperature record while global population keeps increasing on a finite surface. How to quantify it, is another question. If you could uncover a good reason why the UHI effect should not be ergodic, that would be a true contribution (as opposed to empty accusations and talk about credibility). Debugging is not done by accusing others, but actually uncovering specific errors and supplying a patch that removes it. I think you need a thorough understanding of the open source development cycle which is much closer to what is possible in the blogosphere than the old-fashioned scientific publication cycle with its closed peer review system. At least in software development this method is proven to be competitive with more traditional quality assurance procedures. Of course before this kind of publication process can get useful in exchanging ideas at least some revision control infrastructure has to be put in place, but that's another story. Anyway, if you do not do it yourself, you have to wait some more for a meaningful and transparent analysis of UHI along these lines with all the statistics you may wish for, as unfortunately I don't have much time to do it for free. While we are at it, the inconsistency between models and observations in the tropical troposphere can be resolved in a simple way if we assume the surface temperature trend has a long term warming bias (a.k.a. UHI). As the selection criterion of models included in Douglass 2007 was their consistency with the surface record and the "hot spot" has no any direct relation to CO2, just to surface temperatures whatever the cause behind them happens to be, if surface temperature trends are adjusted sufficiently downward, they can get consistent with both tropospheric trends and with a different set of models, selected to conform to reduced surface trends. In this case one would select the models that somehow avoid increasing overall IR opacity between 20N and 20S in spite of some increase in opacity in the CO2 band. These are precisely the models with a negative water vapor feedback in the tropics.
  31. The Big Picture (2010 version)
    Dan Olner #11 Many things could falsify the "AGW theory". Less downward longwave radiation in the last few decades, for example. Or more OLR with some corresponding other forcing that would justify it in quantity. That would mean all those extra GHG in the atmosphere are not having an effect. Which would mean well-established theories like Beer-Lambert Law and Planck Law would be wrong (they are actually so well established that they deserve the status of "laws"of physics). That's why dana said that "our fundamental understanding of physics [would be] be wrong".
  32. The Big Picture (2010 version)
    Gah! Sorry, should have added this before: what's most perverse and enraging about the denialosphere is that no falsifiable theories are ever proposed - or when they are, and they're falsified, they just duck and dodge. And then some have the temerity to accuse climate scientists of being unscientific? Graaah.
  33. The Big Picture (2010 version)
    Just to add: good theories carry on standing up against attempts to falsify - here's a story I just read where Einstein's work once again survives. As they say, "our results agree with Einstein's theory – we weren't expecting any discrepancies and we didn't find any."
  34. The Big Picture (2010 version)
    Nice article. One criticism: Quote: "Sometimes people ask 'what would it take to falsify the man-made global warming theory?'. Well, basically it would require that our fundamental understanding of physics be wrong, because that's what the theory is based on." I think people asking that question - 'what would it take to falsify the man-made global warming theory?' - are making an ostensibly reasonable request, since falsification is one way of demarcating scientific from non-scientific theories. But usually it's used by denialists to muddy the waters and claim that climate science is not falsifiable and thus not 'proper science', because it proposes no theories or statements that are falsifiable. Here's a UK libertarian example. Here's my philosophy of science 101 take on this - would love to hear better informed views. "All swans are white" is a falsifiable theory; if you find a black swan, theory falsified. In the same way, Einstein's theory of relativity is falsifiable - Eddington took photos of an eclipsed sun to measure the predicted impact of gravity on light from a distant star. The theory wasn't falsified - but in principle, it is. That's a criterion for good science - unlike, say, "George Bush is a 12 foot shapeshifting lizard from another dimension". "But he looks human." "Exactly." AGW theory appears unfalsifiable because - it would seem - we need some future date to arrive before the theory can be falsified. It's quite a nice trick: it does appear at first glance that we have to wait for some point in the future to falsify climate theory - and, of course, if the climate does warm, that only confirms the theory, it doesn't falsify it. They're wrong, though. Surprise surprise. Two ways they're wrong: first, if AGW won't be falsifiable until some point in the future, that ALSO means anti-AGW hypotheses are equally unfalsifiable - if they require us to wait for the future to find out. (Actually, of course, AGW theory does make future, falsifiable predictions, but let's put that aside for the moment.) So the next question is, do we need to wait for the future before we can have any faith in climate science? No - there are supporting pillars that are falsifiable. You can come up with plenty of null hypotheses: for example, the earth isn't warming. To turn that round, "The earth is warming" is entirely falsifiable, in principle. Same as the theory of relativity, it just hasn't been falsified - and likely won't be. Clearly, the null hypothesis - say, "the earth hasn't warmed since the 1950s" has been. How about "humans don't cause global warming?" Well, it would need breaking down a bit, but that's easy enough: "co2 doesn't cause atmospheric warming" and "humans aren't putting co2 into the atmosphere" are trivial to falsify. So again, it's just one of those lovely, sciencey-sounding things that 'skeptics' like, but that actually supports their argument not at all.
  35. The Big Picture (2010 version)
    cruzn246, no temperatures have not stayed completely static in any 30 year (or 30 minute) period ever. However, they have also never shot up a degree C in a hundred year period without a specific cause. In this case, the cause is us.
  36. The Big Picture (2010 version)
    Very good post. Small addition: Where you write "In fact we expect human greenhouse gas emissions to cause more warming than we've thus far seen, due to the thermal inertia of the oceans (the time it takes to heat them)." Aerosol cooling is another important factor that we haven't yet seen the full amount of warming that one would expect from GHG emissions. See eg Ramanathan and Feng (2009) http://www-ramanathan.ucsd.edu/publications/Ram-&-Feng-ae43-37_2009.pdf or Raes and Seinfeld short piece in AE last year.
  37. The Big Picture (2010 version)
    C'mon Hunt. Do you really expect the average reader of the sports pages to dive into the fiercely technical waters at Real Climate or Science of Doom? The whole objective of John's project of 1) identify a single argument then 2) describe the scientific background at 3 levels from simple through to full-bore science essay is designed to allow people who get stuck in an argument with a doubter of the science to back up their points with accurate material - pitched at the right level. It's not the writers who are reinventing the wheel, it's the conversational, opinionated know-nothings who revive and recycle the same old talking points.
  38. The Big Picture (2010 version)
    Blah, blah, blah. The claim that man is responsible for virtually all warming is pure speculation. To say that is to assume that temperatures would have basically stayed the same over this whole period. Temperatures have not stayed static for any thirty year period ever.
  39. Climate Change: The 40 Year Delay Between Cause and Effect
    Author's Comment: The Time Constant of Climate Change In the lead article I used the paper by James Hansen and others (ref iii) as a credible estimate for climate lag. His paper states: "Evidence from Earth's history and climate models suggests that climate sensitivity is 0.75° ± 0.25°C per W/m2, implying that 25 to 50 years are needed for Earth's surface temperature to reach 60% of its equilibrium response." My article qualifies this estimate with the comments about the "difficulty in quantifying the rate at which the warm upper layers of the ocean mix with the cooler deeper waters". When I wrote the piece, I was also aware of a paper by B. Lin and others * that uses a different assumption about ocean heat transport. It states: "The estimated time constant of the climate is large (70 - 120 years) mainly owing to the deep ocean heat transport …" CBDunkerson’s comment #9 is useful here. The figure he provides of 0.027 W/m2 for the deep basins is a great deal less than the 0.85 W/m2 at the top of the atmosphere. Therefore I reserve judgment on Lin’s estimate of the time constant, and have chosen to use that provided by Hansen as a starting point for debate. Now the time constant is the time it takes for the system's step response to reach 1 – 1/e = 63.2% of its final equilibrium value. If we take the mid-point of Hansen’s range for 60% warming, 37.5 years, and convert it to a 63.2% warming, by my calculations the resulting time constant is 40.9 years. There is not really any joy for skeptics here. All the papers make clear that at this point in time, we are still talking about estimates. The point of the article is that climate lag is real, it is measured in decades, and it has provided cover for skeptics who dispute the science of global warming. Climate lag means our situation is more perilous than most of the public perceive, and decision-makers need to be made aware. In 5 years or so, I expect we will have more deep ocean data, and be able to estimate the time constant with more certainty. In the meantime, I think 40 years is an appropriate number with which to engage the public. * Atmospheric Chemistry and Physics Discussions, Estimations of climate sensitivity based on top-of-atmosphere radiation imbalance, available at http://www.atmos-chem-phys.org/10/1923/2010/acp-10-1923-2010.pdf
  40. Positive feedback means runaway warming
    9, hadfield: The intent of the post is to address a specific logical question: "How can there be ANY positive feedback if the Earth hasn't done a temperature runaway already?" To that end, a mathematical model is given as an example of a system displaying both positive feedback and non-runaway behavior. This post does not propose to describe the full picture of the dynamics of global warming. You might take a look at the "Advanced" version for more perspective.
  41. The Big Picture (2010 version)
    If I may pose a heretical question - and no offense meant - valuable as these introductory-level posts may be, wouldn't it be better for our expert authors to break some new ground, e.g. by undertaking new research or having new insights, rather than reinventing the wheel (that is, by restating well-known facts in simple terms)?
  42. A detailed look at Hansen's 1988 projections
    I know this is a bit off topic, although it is in context of the present discussion.My own accusation of BP's possible engagement in scientific dishonesty or incompetence is based on data he's presented on this site. He could make the problem magically go away if he just responded to the problem, but so far he seems reluctant to do so. I don't feel particularly inclined to let this go until he does come up with the goods, as his credibility as a commentator on this site hinges on it.
  43. Billions of Blow Dryers: Some Missing Heat Returns to Haunt Us
    KR not to simply punt, rather because it's so complicated and I don't really know how to answer your question, probably the best way to start tracking down changes in circulation would be to dig into the P&J paper's references. In particular you might want to check Orsi's On the meridional extent and fronts of the Antarctic Circumpolar Current (full text, PDF) and follow citations of that paper forward in time.
  44. Climate scientists respond to Monckton's misinformation
    An insignificant point really to Dr. Verons response to Monckton's faulty logic; but on page 5 of Climate Scientists Respond there is the statement by Dr. Veron: "There were no corals in the Cambrian, symbiotic or otherwise: they had not evolved then." Maybe I'm missing something but some seemingly reliable internet sites state that corals did exist in the Cambrian. Maybe I'll have to dig out that 25 year old Historical Geology text. Anyway, a devastating rebuttal to Monckton. Cheers!
  45. A detailed look at Hansen's 1988 projections
    Hi John, Thanks. Yes, I agree it was implicit, but best to be clear I guess.
  46. A detailed look at Hansen's 1988 projections
    Philippe @104, "I advocate for the the moderator to strike any and all future posts that even remotely suggests fraud if there is no supporting evidence" I'll second that. The blog policy currently states that: "No accusations of deception. Any accusations of deception, [fraud], dishonesty or corruption will be deleted. This applies to both sides. Stick to the science. You may criticise a person's methods but not their motives." Humble suggestion is in square brackets.
    Response: Fraud was implicit (doesn't that equate to deception, dishonesty and/or corruption?). Nevertheless, I've updated the Comments Policy to include fraud, just to make it explicit.
  47. Global warming and the unstoppable 1500 year cycle
    Re: archiesteel (30) Thanks for the compliment. One thing I have learned from this (I try for a positive takeaway whenever possible) is that certain individuals come to forums such as this to...see what reaction they can stir up. Like a petulant child continuing to throw rocks at a bees nest when told repeatedly to stop. By emulating Gavin Schmidt or John Cook instead of Tamino (while fun, just isn't my style) I think I can be of better service to more questing here. And it won't feed into the rock-throwers. More On-Topic: If we now are experiencing record heat & thawing in the Arctic, shouldn't we be experiencing record cold and sea-ice & ice sheet advance & mass-gain in the Antarctic? Oh, that's right, sea ice diminishing there, too; net mass-losses in both the WAIS and the EAIS...guess this post by John Russell is spot-on. The Yooper
  48. Industrial CO2: Relentless warming taskmaster
    "he unremitting rise of CO2 from industrial activities has become the dominant factor" I don't know if this is the best thread for discussion of Davis, Caldeira and Matthews in the 10 Sept issue of Science. They've analyzed the carbon-consuming capacities of existing industrial and consumer sectors and done some future projections. We calculated cumulative future emissions of 496 (282 to 701 in lower- and upperbounding scenarios) Gt of CO2 from combustion of fossil fuels by existing infrastructure between 2010 and 2060, forcing mean warming of 1.3C (1.1 to 1.4C) above the pre-industrial era and atmospheric concentrations of CO2 less than 430 ppm. This doesn't square very well with Raupach et al. 2007, especially the figure shown here: Pick your favorite scenario, but we've never turned things over the way the 450ppm stabilization requires. So a mere +1.3C doesn't seem like a reasonable forecast.
  49. The Big Picture (2010 version)
    MattJ - the question about model should refer to Models arent reliable argument. But yes, models most certainly do take into account clouds and aerosols. The closest thing to "fudge factors" would be parameterizations - empirical equations that relate some variable response to inputs. (eg evaporation as response to sea-temp, wind etc). However, it is important to note that the "tuning" of empirical determinations match a specific variable to factors affecting it, NOT to fiddling knobs so that you match observed climate to model. Have a look at this FAQ for example. Further questions to appropriate argument (or ask the modellers themselves).
  50. A detailed look at Hansen's 1988 projections
    The "fraud" thing is a magical incantation, a clumsy way of wishing away facts, not scientific.

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