RealClimate logo

Technical Note: Sorry for the recent unanticipated down-time, we had to perform some necessary updates. Please let us know if you have any problems.

Lawson vs. the IPCC

Filed under: — gavin @ 9 November 2005

Nigel Lawson, one of Britain’s Chancellors of the Exchequer during the Thatcher Era (Secretary of the Treasury for those needing a US translation) and more recently known as the father of Nigella Lawson (a UK cooking diva), has weighed into the climate debate with a recent broadside calling for the abolition of the IPCC (Intergovernmental Panel on Climate Change). Based on a curious report by the UK House of Lords Economics Affairs committee (in which they made clear that they had no scientific expertise), Lawson demands that the only global scientific assessment process on climate change be shut down, and replaced with ….well what exactly?

It is worth re-iterating what role the IPCC and other scientific assessments (another example being the WMO biennial report on ozone depletion) are supposed to play. Even for experts in any particular field (and definitely for policy makers), the vast scientific literature needs to be distilled and summarised. In the first instance this must be done by scientists who are in that field and familiar with it. Where there is a widespread consensus, and where there are substantial debates or important uncertainties should be made clear. Open expert review is crucial in ensuring that these distinctions are agreed to by most of the field.

It should go without saying that the assessment bodies should be international in scope to avoid the impression that they are somehow pushing national agendas in very sensitive areas such as energy or trade. It is also vital that the process of scientific assessment is completely separate from the any proposed policy recommendation: the science should inform the policy, not determine it. To that end, there are three working groups in the IPCC: Working Group I deals with the scientific issues regarding climate change (and is the group that we at RealClimate are most involved with), WG II deals with potential impacts, and WG III deals with potential policy options.

The heart of Lawson’s case is the economic criticism of the IPCC scenario generation process which has been pushed by Ian Castles and David Henderson. We are not economists and so we won’t engage in the specifics of this criticism, but as consumers (so to speak) of the product, it’s worth making a couple of relevant points. First, it should be emphasised that the scenarios are used solely for the providing input into climate models, and not for generic economic planning decisions. Therefore only the final differences in the total greenhouse gas emissions actually matter. From reading the Committee report itself, these differences in emissions for one particular scenario are only around 15% by 2100, and only lead to a 0.1 deg C difference in temperature by 2100 (Table 3, p39) – and this is certainly much less than the spread among the different storylines, and so is unlikely to affect the range of climate model results.

A second point worth making is that IPCC is not the sole supplier of scenarios. The GISS group has developed its own ‘alternative scenarios’ (assuming relatively aggressive attempts to reduce emissions for instance, something IPCC explicitly does not consider), and any other group is free to do the same. If they are significantly different from the standards, other groups could be expected to run them as well. In and of itself this line of criticism clearly does not imply that IPCC should be abolished as an institution, since of course the scenario generation and their use in future projections only makes up a very small part of the scientific assessment process.

However, Lawson’s claims that IPCC’s ‘ignoring of dissent’ is a ‘scandal’ betrays a fundemental ignorance of how the IPCC works. The last IPCC report (TAR) was published in 2001. It will assess the validity of any criticisms published in the scientific literature in its next report, due in 2007. The IPCC makes its assessments in a very thorough writing and review process involving hundreds of scientists, open to critics, with transparent and predefined procedures. That it makes no proclamations in between the full assessments is not a ‘scandal’, it simply is sticking to its sound and transparent procedures.

The vast majority of studies since TAR have reinforced the conclusions made then, and so it is likely that the 2007 report will be very similar in its conclusions. Of course, it isn’t possible to keep everyone happy, so what happens when small but vocal minorities start complaining that they have been shut out of the process, their views marginalised and the ‘establishment’ is somehow persecuting them?

Much of the time these ‘outsider’ critiques are not based on anything other than a desire to confuse (claims that IPCC doesn’t mention water vapour feedbacks for instance, or that there is a deliberate attempt to downplay solar effects on climate or that the number of vineyards in England a thousand years ago implies that CO2 has no radiative effect) and have no traction in the scientific community. These critiques are therefore easily dismissed. More substantive potential criticisms based on peer-reviewed literature (which may or may not be correct) have to be considered more carefully in the context of similar studies and relevance, and that is generally what happens. In the end though, most outlier results do not end up in the mainstream, though investigating them often leads to a better understanding of the process (Lindzen’s Iris effect is a case in point).

However, the bulk of Lawson’s case actually appears to stem from a confusion between the IPCC and the policy options exemplified by the Kyoto Protocol. These are two quite separate things. As Roger Pielke Jr is fond of saying (and with which I agree), scientific description of a problem does not imply a specific policy response. In this case, while the Kyoto process is an attempt to deal with the problems highlighted by the IPCC, it was neither suggested, nor prescribed, by that body. Therefore, what balance between adaptation (dealing with whatever happens) and mitigation (doing something about the emissions that contribute to climate change) is likely to be more cost effective is not a question within the remit of the IPCC (although many options are discussed in the WG III report). One point worth making is that if Lawson really feels that the high end emissions forecasts are unrealistic, then the costs of keeping to a climate-based target are much less – ‘Kyoto for free’ as it were.

Lawson suggests that economic issues related to climate change should be discussed within economic departments of government, and I doubt anyone would disagree. He goes further though and calls for the dismantling of the IPCC and it’s functions to be transferred to the existing Bretton Woods institutions (that is, the World Bank and the International Monetary Fund). This is surely a mistake. IPCC is tasked with the scientific assessment of climate change, handing that function to economic institutions not heretofore known for their scientific expertise would surely be an error. Just how much of an error is revealed by Lawson’s last paragraphs in which he, ironically, he uses the notion of a scientific consensus to combat (admittedly widespread) popular claims of a direct link between the individual impacts of Hurricanes Katrina and Rita and global warming. Since no scientists have made a claim of direct cause and effect (see our recent post on potential statistical links between hurricane intensity and tropical warming), any scientific assessment (such as the next IPCC report) will certainly not do so either. It is precisely because such anecdotal ‘science’ is not a balanced picture of the state-of-the-art that IPCC exists in the first place. And if IPCC did not exist, it would be necessary to invent it….

Update 20 Dec 2005: The response of the UK government to the HoL report was published Nov 28.

83 Responses to “Lawson vs. the IPCC”

  1. 1

    It is not surprising that a banker like Nigel Lawson should want the IPCC dismantled. As a chancellor in the Thatcher government he was, and remains, a strong advocate of the ‘free market’, dedicated to unrestricted economic growth.

    IPCC pronouncements, upon the growing body of evidence regarding the reality of climate change, put doubt in people’s minds about the wisdom or plausibility of the untrammelled growth that Lawson favours. The best way around this, obviously, would be to get rid of the body that keeps pointing out inconvenient truths, and hand over the reporting function to bodies more sympathetic to the free market posture.

    Whether such bodies have relevant expertise is immaterial, of course. Actually it would be rather better if they had no such expertise. It would be the equivalent of blindfolding the city guard, so that they cannot see the barbarians coming over the hill. Thus, there will be no calls of alarm from the walls to disturb the trade of the market place below.

  2. 2

    I love when people who couldn’t write the Schwarzchild equation to save their lives weigh in on the science of climate change. Kind of like creationists with engineering degrees talking about biology. What is it about the modern culture that makes people think anyone’s opinion, no matter how little they’ve studied an issue, carries equal weight to anyone else’s?

  3. 3
    Nils Harder says:

    To comment on a particular point of the original article – what kind of a stupid idea: Because the economists failed to establish an equally important body like the IPCC is, one of them demands to shut it down and re-establish it under the Bretton Woods institutions, and he does so with an absolutely unprofessional conglomeration of wild assumptions, even mixing up the IPCC and the Kyoto Protocol. I really wonder how Lawson comes to the conclusion that next to the IMF´s offices there would be a more open and transparent process, as will anyone else wonder who once tried to understand the IMF´s policies. It´s even more disturbing that he does not even have the imagination of creating a SECOND body which tries to make an equally profound assessment of the economic issues of global warming, as the IPCC does of the scientific issues of climate change (or as the UN Millennium Ecosystem Assessment did of all ecosystems). So this economic-based new body could use the IPCC´s findings, trying to work out effective and necessary instruments of mitigating of and adaptation to global warming. But I seriously doubt that the IMF would get along with taking a back seat in this game, relying on what climatologists send to it an then working out something that might really help preventing a global warming exceeding 2 degrees celsius.

    [Response: Actually, it's fully within the scope of WG II to discuss models of the economic impact of climate change, and to discuss economic models of the cost of mitigation (i.e. emissions reduction). To some extent they actually do this. WG III does many of the rest of the things you argue for. This includes things like evaluating technologies for carbon sequestration and carbon capture from power plants. It even includes "meta economics," or the evaluation of various ways to evaluate costs and benefits. At one point, there did seem to be a move within IPCC to have an economic modelling assessment parallel to the physics of climate assessment in WG I, but this fell apart because the people involved in the process seem to have become persuaded that the state of the art of economic modelling -- or even the question of whether costs and benefits can be measured as money at all -- were not up to the task. Thus, all the statements regarding economic modelling and damage estimates are very much hedged and often rather vague. It's just a reflection of the poor state of the art of economic modelling (a view to which not many practicing economists subscribe, unfortunately) --raypierre]

  4. 4
    Timothy says:

    Re: #1 I believe it’s called post-modernism.

    As an aside, I recently read that the IPCC process was originally set up because the US insisted on it in order to control what climate scientists were doing [and saying] because they [the US politicians] weren’t happy with pronouncements made by scientists at various conferences [Villach I think?].

    Is it correct that non-scientist government officials are directly involved in the final phase of agreeing on the text of the IPCC reports?

  5. 5
    Magnus says:

    My, problem with this though, is that the low case scenario seems to be estimated on (maybe) unrealistic growth. Ok so fair enough it seems like it isn’t that important (hence the 0,1) but do we know that? What kind of effect would a lower growth have on the lower temperature border (estimation)?

  6. 6
    Roger Pielke Jr. says:


    A few thoughts. First, I don’t know anything about Lawson, but the IPCC does have some problems. First, its working groups II and III have very much taken on the role of the FCCC’s Subsidiary Body for Scientific and Technical Advice (SBSTA),the group convened to give advice on implementation of the FCCC amd Kyoto. That is, the IPCC WGs II and III have turned their focus to issues related to the implementation of Kyoto, which is quite contrary to your assertion of policy independence. (And note that WG III does not focus on policy as you suggest, that was its focus in the FAR, but no longer, now it is mitigation.) One result of this focus on Kyoto and the FCCC is that the WGs downplay the role of adaptation in climate policy (this was very much the spirit of my comments on one of the AR4 WGII chapters that I reviewed). I discuss how this has come about in some depth in this paper:

    Pielke, Jr., R. A., 2005 (in press). Misdefining Climate Change: Consequences for Science and Action, Environmental Science and Policy.

    Second, you assert incorrectly that “no scientists have made a claim of direct cause and effect” between global warming and hurricane Katrina. Not true. In fact, the lead author for the IPCC WG I chapter on hurricanes has made exactly such a claim. In a peer-reviewed paper? No. In a congressional briefing. See slide 18 here:

    Perhaps there are good scientific reasons for making such a claim, but they probably should go through peer review before being announced as fact (with no sense of uncertainty!) before policy makers. Especially when other scientists, like Kerry Emanuel, assert that such precise attribution is not possible. And further, given that the IADWG has published in JOC May 2005 that attribution of trends in precipitation to GHGs has not yet occurred, it stretches the credulity of this non-climate scientist to think that such precise attribution is possible for specific events. Such reckless action with science in policy do not give friendly outsiders confidence in the IPCC process. They also give plenty of grist to unfriendly IPCC opponents.

    The IPCC has accomplised a lot, but it’s handling of many issues suggests that there might be room for some improvement in its practices. I can make a strong case that the IPCC can improve its connections with the policy process, e.g., by explicitly discussing policy options in WGIII. Given that complaints are mounting, folks involved in the IPCC might listen carefully to them before circling the wagons.

    [Response: Roger, thanks for your comments. I happy with the idea that IPCC can do better than it has, and judging from the AR4 results that I have seen already, I think it is making steps. However, much as I don't want to get into an argument here about hurricanes and climate change, you appear to be putting words into Trenberth's mouth. He does not claim that Katrina was caused by global warming, and I'm surprised that you continue to interpret his words now and last year to conclude this. He has claimed that global warming is changing the background in which hurricanes form (which is clearly true), but that can in no way be construed as arguing that Katrina can be directly attribtued to global warming. Trenberth is as aware as we are that individual events are not attributable in the sense that Lawson implies, and any consensus statement on the issue will agree. Let's not be distracted by semantics. -gavin]

    [Response: I'd be the first to agree that the WG II and WG III reports in many ways seem less focused on a task and less useful than the WG I reports. However, unlike Roger, I think this mostly reflects the very poor state of the art of impact modelling, whether economic or biological, as compared to physical or geochemical modelling. This isn't likely to change anytime soon. These working groups are doing the best they can with a practically impossible task. I can't speak for AR4, but Roger's criticism is off-base with regard to the WG II and WG III reports in the TAR. These reports inevitably stray a little bit into policy areas, but they do a quite valuable job in summarizing things like technical options for carbon capture and sequestration, and of evaluating methodologies for policy decisions. I know Roger is a strong partisan of adaptation over mitigation, but I have never found this approach very convincing, except in certain limited cases. There's a case to be made that the balance in discussion between adaption and mitigation shown in the IPCC reports just reflects an honest appraisal of the limited success technology has had in things like helping natural ecosystems adapt to human-caused environmental change. Just ask how much technology has helped endangered salmon survive dams, or how many endangered species we've rescued by technological fixes. --raypierre]

    [Response: Looking at this from across the Atlantic, I cannot help but be amazed once again at the style of discussion in the US. I looked at Kevin Trenberth's slides. He presents an entirely reasonable analysis, stating little more than the obvious: that global warming has contributed to warmer ocean temperatures, and that warmer ocean temperatures affect evaporation and precipitation associated with hurricanes. Any good physicist would follow this up with a back-of-envelope estimate of how large this effect might be, and that's what he does for the example of Katrina. He does not argue Katrina was caused by global warming, he merely argues that the warmer ocean temperatures have probably enhanced the associated precipitation. I find it very worrysome that a natural scientist who presents a reasonable physical argument is publically accused of "reckless action" from political science quarters. I feel such an ad-hominem attack has no place on our site. It serves to stifle rather than nurture the kind of dispassionate, unideological science discussion which our site is devoted to. It is fine if you want to take issue with Trenberth's argument - but please present a scientific argument why you think warmer temperatures would not enhance hurricane precipitation.
    I also find it strange that Pielke criticises Trenberth for saying something that is not yet published in the reviewed literature. What are such briefings for: to get a first-hand impression of current thinking of scientists, or for scientists to read out sentences from their papers?
    Finally, I find it strange and revealing that Pielke writes: "Such reckless action with science in policy do not give friendly outsiders confidence in the IPCC process." With due respect to his strong opinions - criticism of the IPCC should at least be based on a minimum of understanding how it works. I also do my duties for the next IPCC report, like several hundred other scientists, and I can assure you that the IPCC does not in any way limit our ability to act as individuals in what we say in the public. For the IPCC we meet and discuss the scientific evidence and we write a report about what is widely agreed amongst us. If you want to know what the assessment of the IPCC is, read that report. When you read what I have to say on Realclimate or elsewhere, this is definitely not the IPCC assessment, unless I cite the IPCC as the source, and the same holds for Trenberth or any other scientist contributing to IPCC reports. Therefore, it is just ill-informed to criticise the IPCC process for anything that I might say in public. -Stefan]

  7. 7
    John Tweller says:

    The IPCC can ignore the world’s leading economists and statisticians with impunity, because it has the support of ‘the worldwide scientific community’. In its submission to the House of Lords Committee, the Royal Society (UK) explained that:

    “The work of the IPCC is backed by the worldwide scientific community. A joint statement of support was issued in May 2001 by the science academies of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden and the UK. It stated: “We recognise the IPCC as the world’s most reliable source of information on climate change and its causes, and we endorse its methods of achieving consensus.”

    I almost agree with this, but there are some some unclear places.

    John Tweller

    [Response: It's not so much ignore... I don't think that they should or will, on the CO2 scenario generation side. IPCC "does" climate science, economists do economics. This is fine. Climate modellers, and hence the IPCC, needs future CO2 scenarios. That's not climate science, but they needed it, so they made some (in collaboration with economists). There is a very good case for people like the HoL Economics Committee, or Castles and Henderson, getting off their bums and actually generating their own scenarios instead of just criticising from the sidelines. My suspicion is that the reason they have not done this is because they know full well that they will get much the same result - William]

    [Response: A small correction: IPCC WG I "does" climate science. In fact, IPCC WGII and WGIII "do" economics in more or less the same sense that WGI does climate science. Differences in the way the different groups handle their disciplines are striking, though. While there are many standard climate models to intercompare, and agreed yardsticks to compare them against, there is no analogous suite of economic models. In many cases, economic models (like the WEFA one used to argue against Kyoto) are proprietary, so you can't even see the equations used. Economists do not seem to have a big culture of model intercomparison and verification. This lack of the state of the art, I think, is one of the reasons that the focus in WGIII shifted from its original conception in the SAR (the notorious case where one draft valued Indian lives at one tenth the value of First World lives, leading to a conclusion that you could kill 10 Indians with heat waves but save one American from death by winter cold, and it would all balance out). A laudable exception to the generally dismal scientific standards in the economics community is Bill Nordhaus' modelling effort. For all its faults and shortcomings, about which Bill is very clear, the model is completely transparent, peer-reviewed, and reproducible. I am planning to write a RealClimate piece eventually covering these issue, but focusing on the issue of climate damage functions so we don't stray too far from the RealClimate mandate. --raypierre]

  8. 8
    Roger Pielke Jr. says:


    Thanks. Slide 18 in Trenberth’s presentation that I linked to unambiguously attributes 1 inch of Katrina’s rainfall near New Orleans to global warming. These are Trenberth’s words, not my interpetation of them, presented as fact in a policy briefing, not as hypothesis in a scientific meeting. This is a clear and precise attribution of the effects of GHGs to the behavior of a single storm. The photo next to the statement of attribution is of flooding and damage. This is not an issue that can be dimissed as semantic. Have a look at the slide.

    [Response: I read the slide, and frankly, even if the context in which Trenberth placed the comment is as you assume, it is still not a direct attribution of a specific hurricane to global warming. To keep belabouring this point, it is quite clearly not what Lawson is referring to. -gavin]

  9. 9
    Eli Rabett says:

    Trenberth did say something both to the point and scary, to wit, that based on studies of hurricane INTENSITY, he calculates that 1″ of extra precipitation was dumped into area around New Orleans because of global climate changes. This would be about a 10% increase. It would be interesting to figure out how much this contributed to flooding across the affected area, not just in NO.

    Trenberth is making a direct attack on the arguments of BOTH Pielkes. In the case of Roger Pielke Sr. he points out that global changes has important LOCAL effects also (there is an interesting report and perspective in a recent Science about how global trends are amplified in the Artic). It also directly contradicts Roger Pielke Jr.’s peddling of the idea that no globally climate change connected consequences have yet (if they ever will) been seen in hurricane damage). Pielke Jr. in particular is trying to assert ownership of the issue and needs to be pushed back.

  10. 10
    Lynn Vincentnathan says:

    I haven’t been keeping up with the IPCC reports, after reading some of the 1995 report. I had been following the science journal articles on GW (for my thesis on environmental victimology), and I felt SAR was pretty bland. So I’m way on the other side of the debate from Lawson.

    I think world policy should be: hope for the best, prepare for and try to avert the worst. So my sight is trained more on the higher end projections, and goes beyond 2100.

    My personal policy: become energy/resource efficient & conservative & save gobs of money, while saving the environment from GW, acid rain, local pollution, in addition to mitigating numerous other problems by the same actions.

    I wonder if Lawson might be tied into some dinosaur industry that might go extinct if people really started solving the GW problem. Because the excuse that he’s concerned about the free market doesn’t seem to hold water. What we really need is more freedom, so entrepreneurs can invent and produce stuff that saves the world, without being stomped on by dying dino industries. Maybe we should take the gloves off completely, and do away with all subsidies for fossil fuels (including war costs) and internize (make them pay) ALL harms – from GW, acid rain, local pollution, etc. Then let’s see who wins the free market game.

    [Response:Well, the IPCC summarises and asesses the scientific literature, so if you have managed to keep abreast with the scientific literature on climate and global change, then there should not really be a strong reason for plowing through the IPCC reports (other than that they give a nice summary of the state of the science). In fact, by criticising the IPCC prosess, I believe that Lawson misses the point, as I see IPCC as being faithful to the published science on climate change. After all, the majority of the published scientific work on athropogenic climate change seem to point to an enhanced greenhouse effect. I cannot see any 'alternative' interpretations (what should that be, given that there is not much scientific literature suggesting otherwise?), unless you go to other [unscientific] ‘sources’, and I see this as perhaps the failure of the IPCC/climatology community: that interest groups without scientific credentials have managed to plant such false ideas in people’s minds. -rasmus]

  11. 11
    Jeffrey Davis says:

    I think Trenbreth’s slide caption is a result of too much condensing. I’d bet that his Implies 1″ extra rain is in the subjunctive mood with a kind of “If we’re correct on this …” hovering over the entire presentation. I know: his words clearly don’t say that, and I couldn’t point to a construction that would support my interpretation. All I have are my own experiences with trying to condense complex arguments into shorthand.

  12. 12
    Sashka says:

    Lawson suggests that economic issues related to climate change should be discussed within economic departments of government, and I doubt anyone would disagree.

    I don’t know whether you’re able to set up a polling mechanism here but I’ll take a wild guess that at least half of RC bloggers are not interested in any discussions of economic issues. Or, to be more precise, they don’t want mitigation policies to be predicated on such discussions. What they really want is action, ASAP.

    [Response: I think you were more accurate with your first sentence, before you tried to be more precise :-) - William]

  13. 13
    R. T. Pierrehumbert says:

    I have a few additional comments of my own regarding Lawson’s article.

    First, I find it hard to see why the critics of the IPCC scenarios are so up in arms about the story lines IPCC scenario-writers chose for study. As far as I can see, their criticisms have absolutely zero implications for the utility of IPCC climate forecasts as an aid to policy decisions. The WG III report itself describes these as “story lines” representing possible futures, rather than economic forecasts. There is ample range amongst the scenarios to feed the evaluation of a wide range of policy options. If some policy maker (who could well be a British treasury official) thinks that the Business as Usual scenario is too pessimistic (read, too optimistic regarding developing world economic growth), he or she is free to choose one of the lower emission scenarios, of which there are many.

    The other place where Lawson is completely off-base is in his criticism that IPCC ignores adaptation in favor of mitigation. The Technical Summary of the 2001 WG II report states : “WGII’s mandate for the TAR is to assess the vulnerability of ecological systems, socioeconomic sectors and human health to climate change, positive and negative,on these systems. This assessment also examines the feasibility of adaptation to enhance the positive effects of climate change and ameliorate negative effects” The explicit appearance of the mandates to consider benefits of climate change, and to consider adaptation, gives the lie to Lawson’s criticism that the IPCC has neglected such options. Either he does not actually know what is in the IPCC reports, or he is deliberately misrepresenting them.

    If governments so far have chosen to emphasize emissions controls over adaptation, the fault (if there is any) should be laid at the door of elected officials, not the IPCC. It is not the IPCC that led US officials to ignore New Orleans’ need for better flood control — which would have been a sound adaptation to rising sea levels and increasingly intense hurricanes, with now obvious collateral benefits, even without factoring in global warming.

  14. 14
    Dano says:

    To add slightly to RTP’s excellent comment, the scenario analysis used by the IPCC (and other disciplines in the natural sciences) presupposes that adaptive management strategies will be used that are informed by the scenarios developed.

    That’s why the scenarios were developed – to inform adaptive management strategies.



  15. 15
    Roger Pielke Jr. says:

    Ray (response to #6)- You mischaracterize my views when you write, “I know Roger is a strong partisan of adaptation over mitigation, but I have never found this approach very convincing, except in certain limited cases.” This is probably because some people view any focus on adaptation as taboo. I have repeatedly written that we need a greater focus on adaptation, and that adaptation and mitigation must be complements. I have argued against trading them off. And on your “there is a case to be made …” perhaps this is true, but perhaps someone should make it!

    Eli (#9)- Thanks. I have been “peddling” my ideas in places like Journal of Climate, Natural Hazards, BAMS, Nature, Science and other peer reviewed fora. I welcome the “pushing back” that you call for in the form of serious studies in the peer reviewed literature. We are organizing a workshop in 2006 to motivate some of this pushing back. Science advances by people putting forward hypotheses and others taking a critical look. Sometimes certain hypotheses are unwelcomed or inconvenient, and often they are proved wrong. Being proved wrong is no crime in science, particularly if it contributes to advancing knowledge. So please do push back, but with substance. Thanks again.

  16. 16
    Pat Neuman says:

    In reality,

    Scientific description of the global warming problem has most definitely implied specific policy responses. The policy responses from leaders of countries dependent on fossil fuel burning for the “good life” of it’s citizens today have seriously downplayed the concerns that some have about the damage being done to the planet’s future, from fossil fuel burning. Our leaders have followed a policy to do nothing that might threaten the economy for the present, regardless of the well-being for all life on Earth in the future.

  17. 17
    Mark Shapiro says:

    I remain astonished that nearly all the commenters, with the refreshing exception of Lynn Vincentnathan, continue to frame the debate as adaptation versus mitigation, or even more coarsely, as environment versus economy.

    It is possible to reduce fossil fuel use economically. The tools are energy efficiency and renewable energy. People like Amory Lovins of the Rocky Mountain Institute, at

    have discussed the technologies and free market policies to get them implemented, in great detail.

    Of course an obvious first step would be to end subsidies for fossil fuel consumption, but I think that would require us to discuss politics . . .

  18. 18
    Lynn Vincentnathan says:

    RE #12, I think your final sentence, Sashka, is to the real point. People concerned about life on earth want action. Preferrably starting yesterday. The debate has been over for 10+ years regarding whether or not there should be action. So those still pretending there’s a debate…well, I’d better not continue this line or I’ll be deleted.

    But I’m sure it’s occured to some of you that debating the fine print while the book is burning might itself be a strategy. So now the latest strategy is to debate whether or not we should have the IPCC — that ought to keep policy wonks from taking any action for at least another 5 years….

    I also understand the meaning of your 2nd to last sentence. Economics in and of itself is a sterile pursuit, at least in the context of GW, because it considers the earth & its biota (& all the complexities that likely go beyond those that biologists & climatologists can currently tell us about) as “resources” without any limits (life, for instance, can be reduced to monetary amounts — as if any amount of money can bring the dead to life). And they consider the sociocultural system beyond economics as “tastes & preferences.” So economics should not be the sole determinant of our policies, and it shouldn’t even be the leading determinant. It’s just one among many, many other voices to be considered in making decisions. Too bad policy wonks don’t understand that.

  19. 19
    Eli Rabett says:

    Roger: You, and to be fair others such as Chris Mooney, function in an honorable tradition which started with the self publishing pamphleteers of the 16th and 17th century. When enough notice had been achieved a book was/is published. More recently public intellectuals started by publishing in the academic press, working in foundations or universities, with the goal of moving on to policy making positions in government. With good luck they become consultants and movers and shakers. No better example of this than Henry Kissinger. Blogs provide a shortcut for this career path. You had the perspicacity to start your blog early in an area that was not well served.

    What you are doing here, and in your publications, and on Prometheus is to assert ownership of a series of issues, the latest of which is hurricane damage due to climate change. Your incessant self citation is a clear indication. I am certain you will reply that somewhere in a post somewhen you may have mentioned another’s work. You react to any challenge to your theses virulently, and in your replies often distort what others have said, for example your last blow up about the Trenberth slide. In short, you act as a policy person, not a science person. Horrors, at least when this is pointed out. But again, sui generis. This is what one expects of a policy wonk, for example Brad de Long. Yet, you keep telling those of us who reply to you that you are scientifically as pure as the driven snow. I beg to differ.

    If you had a better sense of irony you would have named your blog “Zeus’ Eagle”, not let on to what the reference was, and merrily gone on pecking at the livers of those whose research falisified your opinions.

  20. 20
    Mauri Pelto says:

    I am delighted with the forthright nature of Trenberths’s presentation. I have been disappointed with many climate scientists hedging on the role of global warming in hurricanes. I like the analogy of a person with heart disease who approaches a doctor and asks what causes the illness in their case, “Could it be due to my never exercising?”. The doctor would then point out that of course that would have a role, but so would diet, stress etc. We seem to want a singular explanation for causation not just an enhancing role as Trenberth points out warmer ocean temperatures over larger areas for longer would have to have all else being equal. As a glacial researcher for 25 years I am dismayed to have seen five glaciers I observe melt away in the North Cascades of Washington. It is disconcerting to see the magnitude of this change and still be asked if we really are experiencing warming.

  21. 21
    Roger Pielke Jr. says:

    Eli (#19)-

    Thanks for these additional comments, and thanks also for the RC for allowing this brief foray into a subject which I am sure are far beyond the topic here. Let me just offer a quick response to your various points.

    We do use our blog to promote our work and our views. Guilty as charged. We have also published other perspectives and allowed wide ranging discussions. We strive for a high level of respect and courtesy in our exchanges. But make no mistake, we do present some strongly held positions, which are often motivated by a desire for motivating serious debates on important topics on which reasonable people can disagree. We also try to be fair. This is what academics do, and blogs give a window to that world. Often in academia we argue passionately, and they go out for a beer afterwards. And as a professor who teaches policy, and directs a policy center, and publishes on policy, I am focused on policy issues. Again, guilty as charged. I do feel strongly that policy research should appear in the peer reviewed journals, and we try to share what we publish and its significance on our blog. Our blog is an experiment, and with constructive feedback we hope that it improves and contributes to informed debate on contested issues that people have strong feelings about.

    Finally, I simply reject the notion that we have in any way mischaracterized what Trenberth has said, but readers of our blog can and should make up their own mind. Reasonable people can legitimately disagree on complicated, important subjects. Thanks.

  22. 22
    Steve Latham says:

    I don’t think this strand is supposed to be about Trenberth, so I apologize, but I read through that slide presentation and think that you can’t know what it means unless you were there to hear the words accompanying the presentation. He says (in my opinion) that if you work through his equations, then Katrina got an extra inch all else being equal (to borrow the phrase from #20). The problem with attribution for single events is, of course, that all else is never equal. If Trenberth acknowledged that at any time during his presentation then I don’t think Roger’s description is correct.

    Gavin, thank you for highlighting the importance of the IPCC and how you think it should run. Roger, thank you for describing ways it could be better. That is an important side of the story. I think it would be more refreshing and interesting, though, if there could be a post from ‘non-skeptics’ on any positive role that skeptics play (if any) and how that role could be more-productively carried out. An example is suggested in Gavin’s post (Lindzen’s iris effect [no link]). I am not trying to take over this strand but instead want to inspire another one that is related. Here is a start: skeptics should criticize the IPCC, skeptics should ask for access to data and analytical disclosures, skeptics should not criticize the science with economic arguments, skeptics should not put words into the mouths of those they criticize, skeptics should define some goalposts so that progress can be understood from their point of view, skeptics should use the peer-reviewed literature…. Okay, so some of these are boring, too. How about applying the logic Gavin applies to the need for the IPCC — should there be a defined, international panel (with sub-groups and everything) for the skeptics?

    As a scientist I know it’s my job to be a skeptic, but expecting others to leave me to do my work (fisheries science) when it affects their livelihoods is unrealistic. That’s why we have representatives of various groups on a panel that oversees work done by me and my colleagues. And they have hired scientists who explain technical details to them. I believe this interaction properly focuses their anger and imagination and other energies on the policy rather than the science when the science is clear. It allows them to be more effective skeptics (focussing their attention appropriately) when the science is not. Lawson’s demands would have to be different if a watchdog group, respected by ‘both sides’, existed.

  23. 23

    Re : #22

    “As a scientist I know it’s my job to be a skeptic”


    You really need to think seriously about finding another line of work.

    [Moderator: Watch the ad hominem (see our comment policy). We allowed this one through, but next one may not make it if you're not more careful.]

    Or at least do a simple search of “scientific methods” (note plurality).

  24. 24
    Gregory Lewis says:

    re #21: Rabett vs RP Jr.
    I look forward to the exchange but doesn’t Rabitt’s post violate the RC comment policy?
    This is a bit of a personal attack, and an attribution of motives.

    [Moderator: This one walked the gray line, but it was focused on substantive rather than gratuitously ad hominem arguments. So we allowed this one through, but we're watching carefully. Roger provided a thoughtful response, and the exchange was constructive.]

    While I agree with Rabett’s sentiment, I’ve seen similar attitudes from
    a number of other scientists (and often they are the foremost expert in their fields).
    It is very common for anyone to overstate their ideas and positions.

    Re: 22:
    For what it is worth, there was someone there: See the comments on this topic from “OnTheInside” on Prometheus which starts:
    “I was at the Congressional Seminar Series and was surprised by Trenberth’s assertion that global warming may have caused an extra 1″ of rain from Katrina. (He went even further and suggested that the extra water may have been the difference between levees being topped or not.)”

    [Moderator: This sort of hearsay/gossip typically won't be allowed here. We're not in the business of providing a forum for unsubstantiated rumors that are attributed to an anonymous source.]

    This whole episode seems a bit overblown, except as an example of a larger issue. I doubt anyone hearing Trenberth came away with anything beside the impression that one scientist thought it was likely that GW contributed something to Katrina–Unless of course they already had a stronger opinion.

  25. 25
    Steve Latham says:

    Hey Thomas (#22) – ouch, but why don’t you tell me what you mean? Perhaps it would help if I wrote, “it’s my job to be skeptical of my own findings.” Or are you also picking on something else I wrote?

  26. 26

    Re #25 But you are not being skeptical of your own findings. You are being skeptical of the findings of the contributors to the IPCC reports.

    Of course, that is no sin. Peer review is based on the principle of skepticism. Where it falls down is that there is no peer review of the criticism produced by the peer review. A peer reviewer can reject a paper because he is not cited, but no one can criticises that.

    Skepticism does drive science, but we have a right to be skeptical of your skepticism, and reject it!

    Cheers, Alastair.

  27. 27

    #25 -

    That’s the whole point, you didn’t qualify the statement at all. First of all, science itself is not a ‘job’, and if your job is actually working in science, for example, if you are paid by someone to actually do science, then your job is certainly not to be skeptical, your job is to produce usable (actionable) results (right or wrong, well, there really is no right or wrong on the front lines anyways, just results, take em or leave em).

    Unqualified skepticism, that is, scepticism without evidence, is generally not considered as part of the rapidly expanding repertoire of scientific methods. If you have a problem with someone’s methodology or results, then produce your own results which contradict their results, or attempt to falsify their methodology, but it is definitely unacceptable in my repertoire of methodology, to just go after their results, or even their methodology, without first trying to reproduce their results first, or by falsifying their methodology. Skepticism has to be the most widely abused methodology of modern day ‘scientists’. History has demonstrated that over and over again, yet the falsification of skepticism as a scientific method seems not to have generally made it’s way into the mainstream scientific community as of yet, certainly not even into the mainstream economic or political arena. It’s my ‘job’ as a ‘scientist’ to point that out.

    Of course, if your job is to practice skepicism, then you are not a ‘scientist’, at least in my highly annotated and now bulging looseleaf folder of scientific methodologies. On the other hand, it’s fine to be skeptical of your own results, that’s the whole fact checking thing.

    I apologize if I ripped that out of context, but the subject of unjustified skepticism is of fundamental importance to climate science, and many other leading edge scientific disciplines, as the repertoire of scientific methods and methodologies continues to expand with rapidly improving knowledge bases and technologies.

    It you want to falsify a result or methodology, I’m sure you will quickly find that skepticism will be of no help to you at all as a scientific method. Skepticism is just not a credible scientific method anymore.

    [Response: I have to strongly disagree here. Being a scientist means being a professional skeptic (in the true sense of the word). i.e. one doesn't accept statements without good evidence. I'm pretty sure this was the sense that the previous commenter meant. Similarly, I do not need to redo someone's attempts to make a perpetual motion machine to be skeptical about it's existence. More relevantly, if someone claims a significant trend from 2 points on a graph, I don't need to get out Excel to be skeptical of the result. To be sure, 'skepticism' in the climate realm has become synonymous with refusal to accept anything despite good evidence, but that is a distortion of the word and an affront to true skeptics. Skepticism is not per se a 'method' but it is a valid starting point and attitude. -gavin]

  28. 28
    Steve Latham says:

    Hey, this is weird — how did I get dressed in a black hat? I’m not an AGW skeptic. I started writing letters to newspaper editors back in 1996 telling them how their economy-based attacks on the science were wrong-headed. I’m still at it. But what I’m saying is that constructive criticism is good and maybe the energy of AGW skeptics can be put to good use if directed properly. Does anything need to change? My relatively uninformed opinion is that it does, especially if the public elects representatives to act like Nigel Lawson. Alistair’s complaint (#26) that the mud-slinger can’t get criticised is perhaps an argument in favor of a recognized watchdog with a fixed set of principles that it enforces. Such a watchdog might marginalize the real crazies and help the public to separate the reasonable/legitimate criticisms from the inaccurate, inappropriate, and ridiculous. It’s just a suggestion for consideration and maybe discussion at some point in the future. I hoped the idea would be more interesting than, well, who I am.

  29. 29
    Jim Glendenning says:

    You asked what positive effect the sceptics have had. Let me name a few:
    1. They have made AGW proponents redouble their efforts to be accurate and double check their models.
    2. If AGW proponents controlled policy the U.S. would now be throttling back its economy to the especial detriment of the poor.
    3. Sceptics have helped to prevent rash policies that may not have had any effect on GW.
    4. Sceptics have pointed out that if GW is not actually anthropogenic, huge cutbacks in energy production would not help.
    5. Sceptics have pointed out that many of the proponents of AGW are against increasing necessary energy supplies through the use of hydro-electric and nuclear production.
    6. Sceptics have pointed out to AGW proponents that the needed future supplies of energy cannot be provided only by alternatives to fossil fuels.
    7.Sceptics have pointed out that much of the debate over GW is a debate between members of the environmental movement who are against all modern industrial production and those who want to continue the use of all forms of energy to improve the lot of humans.
    8.Sceptics have forced scientists to look at what adapting to GW versus mitigation might entail.
    9. Sceptics have pointed out that there has been a parade of books predicting Malthusian disaster, none of which has come true.

    [Response: I'm also sure a few of the sceptics have also advised that I look both ways before crossing the road. You need to distinguish issues that are/were tackled or thought about without the 'sceptics' (and we know who we are talking about) getting involved, and issues that have been raised only by the sceptics that have actually lead to interesting science. That cuts out items 2 through 9 on your list. However, you could add work on upper tropospheric water vapour feedbacks which were quite clearly motivated by Lindzen's criticisms and ..... errr..... that's about it. (Anybody have some other examples?). -gavin]

  30. 30

    Re : skeptical response

    I think you do agree with me.

    I claim that skepticism as a scientific method, is trivially falsifiable.

    When you are able to falsify a result, you are not practicing skepticism, you are practicing science. On the other hand, when you are able to act on a result, to create new results, you are also practicing science, but with a much better ‘attitude’. Skepticism must be balanced or offset by speculation. Sooner or later you have to have enough confidence to act on your results.

    Skepticism and speculation in science is a whole topic in itself. Science itself seems to be a kind of highly directed semantics. It’s no wonder nobody seems to be able to agree on anything, which is why the hard numbers and the analytical and computational results are so valuable.

    Anyways, I have enough confidence in modern scientific methods, to speculate that smoking all of the rest of our planet’s hydrocarbon resources, by inefficent combustion methods, will not produce the desired long term planetary results, in system with life is a major component.

  31. 31

    Skeptics greatest contribution is that they support pollution!
    May Hydrogen engines clear their minds…..

  32. 32
    Roger Pielke Jr. says:

    Stefan (2nd response to #6)-

    Thanks for your perspective. I appreciate the exchange. Some responses.

    First, let’s be clear, my comments about Trenberth’s representation of science in a political setting in an area where I have some knowledge (hurricane impacts) is not at all an ad hominem attack. RC frequently evaluates comments made in public and political settings by scientists and non-scientists, and the comments in the RC moderated discussions often focus in this direction. I think that such perspectives are valuable if done in a professional manner.

    Second, you ask exactly the right question when you write, “What are such briefings for: to get a first-hand impression of current thinking of scientists, or for scientists to read out sentences from their papers?” If you want to see the current thinking of scientists, go to a professional scientific society meeting. Congressional briefings, which are generally pretty irrelevant, should be for presentation of information with policy and political relevance. Don’t be seduced by thinking that policy makers or their staff have an intrinsic interest in the science. I’d assert that an appropriate role for science in congressional briefings is to present (a) the consensus/diversity of views on a particular topic, and crucially,(b) the significance of that science for action. The AMS briefing met neither of these criteria. Of course, it bears repeating that reasonable people can disagree on such things.

    Third, I agree in general with your point about distinguishing the IPCC from individuals who may or may not be associated. But the reality is that people matter. The public statements by people associated with the IPCC, as well as those in visible roles in the climate science community, like RC, do affect how people view the credibility of the IPCC. You may not like this, but that makes it no less real. Think about how the world looks from Lawson’s perspective (Aha, back on topic!). You emphasize the importance of the IPCC, and the IPCC most recently says no connections of hurricanes and climate change. Some experts say there is a large connection, others say no connection. What is Lawson supposed to think? You want Lawson to be able to pick the “right” expert before the IPCC renders its judgments. On what basis should he choose between Trenberth and Gray? When Gavin makes a statement that many reasonable people could take issue with (hence the Trenberth example), it does not lend to credibility. The point here is not who will be proved right or wrong in the end. Credibility is based on many things and understanding how it is earned and lost is critical to keeping it. Loud defenses of the IPCC and continued invocations of the fidelity of IPCC processes are not recipes for maintaining credibility. You may disagree, but the evidence is in perspectives like Lawson’s which are casually dismissed at some risk. Sometimes people who you disagree with have good reasons for seeing the world the way that they do.

    Thanks again.

    [Response: Roger, my statement was not ambiguous. I stated that no scientist had made a direct attribution of Katrina to global warming. i.e. that Katrina was caused by global warming. Your paraphrase however is incorrect. There may well be connections between hurricanes (in general) and global warming as have been highlighted in the discussions of the Knutson et al, Emanuel and Webster et al papers. The conflation that you make between the two statements (i.e. general connection implies specific cause) may explain why the conversation appears to make no headway. To me these are very different statements. To you (and possibly to policy makers) they appear to sound the same. I agree that it is incumbent upon scientists to strictly delineate statements where there might be a possibility of mis-interpretation and maybe I should have been even clearer in my statements. I should also make clear that I am not part of the IPCC process except as an external expert reviewer. -gavin]

    [Response: I leave it to our readers whether they consider publically accusing someone of "reckless action", and doing this behind their back, an ad hominem attack or not. In your comment # 21 you speak about "a high level of respect and courtesy in our exchanges". Would it not have been just an average level of courtesy to contact Trenberth directly and check with him what he actually said? And if you feel you want to criticise it, do it to his face? He was not even aware what you had written about him on our site. "Understanding how credibility is earned and lost is critical to keeping it." I think that is good advice.
    Could you specify what you're referring to when you say "Loud defenses of the IPCC"?
    And you still have not provided any factual argument of why you criticised Trenberth. That a hurricane would pick up and rain out more water when the ocean is warmer is very reasonable physics - is the political climate in the US now such that one is not allowed to point out simple physical connections? I'm a physicist, and I'm afraid the laws of physics will not be swayed by what policy people like to hear. -stefan]

  33. 33
    Roger Pielke Jr. says:

    Gavin (response to #32)-

    Thanks. I think that you have correctly put your finger on the communication issues here. But I am surprised by your view that your staement was not ambiguous. Clearly it was as you point out.

    Your original post stated, “no scientists have made a claim of direct cause and effect.” If you meant by that the cause being GHGs, and the effect being the very existence of Katrina, then I did not interpret your statement that way. I interpreted your statement as meaning, cause = GHGs, and effect being discernible influence of GHGs on Katrina or its damages. Trenberth clearly did the latter. The former I’d assert is a strawman, which I suppose why I didn’t interpret in the way that you describe (i.e., I can’t imagine Lawson meant that either.)

    You also state in your response to #32, “There may well be connections between hurricanes (in general) and global warming as have been highlighted in the discussions of the Knutson et al, Emanuel and Webster et al papers. The conflation that you make between the two statements (i.e. general connection implies specific cause) may explain why the conversation appears to make no headway.” Let’s be clear, it was Trenberth who clearly made the connection between general conclusion about hurricanes and GW (which I have no reason to doubt, e.g., see out BAMS paper which cites all three papers that you refer to) and a specific event – Katrina and its impacts, in a political forum. Enough said on that. Let’s move on.

    [Response: Let's not quite move on yet. You have strongly attacked a colleague, and you still have not provided any rational argument why his physical reasoning is incorrect. -stefan]

    And while you are not an author in the IPCC process you have engaged in its defense. As a leading voice in this community your views, for better or worse, reflect upon the IPCC.

    [Response: It is getting a little weird. So the IPCC process can be criticised for what any individual climatologist says - no matter whether he is even associated with the IPCC reports?
    And you still owe us the explanation why you called Gavin's defense of the IPCC "loud". That is a put-down, and I think specifying what you meant is demanded by the respect and courtesy that you like to appeal to (which in my view is not measured in the number of times one adds "thank you" at the bottom). -stefan]

    Thanks again.

    [Response: Roger, Stefan, Please let's move on. This issue is a huge distraction from the point of the post - gavin]

  34. 34
    Pat Neuman says:

    Re #32 Response

    Yes, in the US one is not allowed to point out simple physical connections, like how transpiration increases when growing seasons are longer, like how evaporation increases when lakes and reservoirs are warmer, like how rainfall intensity increases when climate is more humid and warmer, like how winter floods increase when climate is more humid and warmer ?

  35. 35
    Lynn Vincentnathan says:

    I think Trenberth’s suggestion of 1″ extra precip due to Katrina is really fairly mild, based as it is on huge regional & world averages, and not on the actual amount AGW may have increased SST & WV in the exact areas that spawned Katrina (which science can’t tell us…yet). (Nevertheless that last extra 1″ does a lot more damage than that first inch, which doesn’t even tickle the levee & is quite welcome by gardeners everywhere.)

    My thinking is this: Trenberth’s inch seems a bit mild & well within the bounds of reasonableness. But what if in a “God only knows” scenario in which humans had never evolved & there was no AGW, the Gulf had been slated to be below normal in SST & precip at the time of Katrina. Then in an “add in the humans” scenario (today’s reality) GW might have contributed nearly the whole Katrina. I think that is within the realm of possibility, even if it cannot be proven one way or the other…yet.

    Policy-makers & lay persons should be considering that high end possibility — not only modest, “best science can do” scientifically cautious statements. The implications are clear – there’s just no excuse anymore not to turn off those lights not in use!

    BTW, by “bland” in my earlier reference to IPCC’s 1995 SAR, I did not mean inaccurate. And the fact that the 2001 TAR gave more robust support for AGW & its possible harms, does show the SAR to be bland by comparison. So I think, acc to sci jnl articles since TAR, the 4th report in 2007 should make TAR seem somewhat bland by comparison — maybe that’s what Lawson is worried about & wants to quash or discredit IPCC before the 4th report comes out.

  36. 36
    Dan Allan says:

    Gentlemen – Stefan, Gavin, Roger, Eli – perhaps you are not aware of how personal and harsh this thread comes across. As a stranger to all of you, I would suggest to you all that a public blog is not the best place to air this. You should all be mindful that accusations are amplified a couple of orders of magnitude when put in writing for the world to read.

    Regarding Trenberth, having looked at the slides, I don’t see Roger’s interpretation, personally, but on the other hand I don’t find his accusation of “recklessness” nearly as ad-hom as Eli’s quite sarcastic and personal rebuttal post. My understanding of climate science has not been increased by Eli’s comparison of Professor Pielke to Henry Kissinger.

    This is unfortunate in what has been, up to now, a terrific site.

    [Response: I agree completely. This is no longer constructive and we should move on to something substantive. Apologies all round. -gavin]

  37. 37
    Gerald Machnee says:

    Re # 35 – You are treating AGW like a religion. You start off by suggesting that Trenberth’s 1 inch of extra rain was mild. Then you go on to suggest that even all of Katrina could be due to AGW. You have no scientific basis for your statements. Wake up, huuricanes have been around during the “colder” periods centuries ago.
    Katrina could even have been worse on New Orleans if the eye had made landfall about 50 miles more westerly. The additional tide would have made the one inch of rain insignificant. Competent scientists have stated that it is difficult to attribute the specific amount of severity of a hurricane to global warming.

  38. 38
    Eli Rabett says:

    In reply to Dan, I agree that this is not the place to continue this thread. Please accept that I had my say and did not continue. I believe that there is a place for such interchanges, but to avoid them degenerating one should not post more than once a day, perhaps less frequently, and allow those who disagree to have time for their reply. In the process of stopping allow me to clear up one point.

    I did not mean to use Kissinger as a negative comparison, but as the best illustration of someone who used his academic writings to move into a position where he could make public policy. A more recent US example might be Larry Summers. With respect to Prof. Pielke, this was meant as a compliment (seriously). He is one of the few who have a very clear idea about how to effectively use a new medium. My issue (continued elsewhere…the bad news for William is that I am thinking to post on this issue on neutral ground at Stoat….

  39. 39
    McCall says:

    Please, gentlemen — Slide 18 is titled:
    How big is the effect of Global Warming?

    Followed by:
    * Since 1970 tropical SSTs have increased 0.5ºC
    * Water vapor has likely increased ~4%.
    * This also likely enhances winds by this order
    * Surface latent heat fluxes in storms likely increase by at least this much [Research topic]
    * Thus moisture convergence in boundary layer goes up by 8% (1.042).
    * Corresponds to expected increases in rainfall and latent heat release in storms: order 8%. [4 to 12%]

    And FINALLY:
    [Implies 1" extra rain near New Orleans in Katrina]

    The fact that Mr. Rabett doesn’t understand this obvious 4 to 12% (8% – when forced to a number) link to GW effects is regrettable; however, the fact that many others here don’t get it, is depressing. With all this concern for fairness and rebuttal of a colleague of many of you (Professor Trenberth), I would like to read a comment from another colleague, Professor Landsea, on whether the above presentation and particularly the summary slide 18 linkage of GW to increased hurricane and specifically Katrina intensity, is an example of why he resigned from the IPCC in early ’05?

    [Response: I think you summarise Trenberth's argument correctly, and it is an entirely reasonable argument. In the thread above I have tried (in vain) to get Trenberth's critics to put their scientific reasons on the table why they think he is wrong, so that we could have a good science discussion. Note that Trenberth discusses a physical connection between warmer ocean temperatures and enhanced precipitation, and the physics applies to every individual hurricane, including Katrina. (He is not talking about a statistical connection, from which no conclusion about one individual event should be drawn, only about ensembles. Maybe confusing those two is what got some people excited.) The physical link between SST and precipitation for any individual hurricane is not controversial, it is routinely exploited in the hurricane forecast models used by the national hurricane center.
    Incidentally, those who claim the extreme 2005 hurricane season is entirely due to a natural cycle, like Bill Gray, also say it is due to warmer ocean temperatures - the difference in opinion is in why the ocean temperatures are so warm, not in the effect this has on hurricane intensity or precipitation. Gray says the ocean is warm because of an increased thermohaline circulation in the Atlantic, which varies as a cycle (see comment #15 here). The reason why climatologists do not believe this is the whole story is because an increase in thermohaline circulation would warm only the north Atlantic, but it would cool the south Atlantic and would have hardly any effect on the Pacific or the global mean temperature. However, ocean temperatures have warmed almost everywhere on the planet, with 0.5 ºC being the global mean rise of sea surface temperature, hence Trenberth's reasonable estimate that this much is the contribution from global forcings like CO2. Superimposed on this are any regional and natural oscillations due to changes in heat transport (which redistributes heat, making some places warm more than average, some warm less or a few even cool). Also, the effect of CO2 on temperatures is very well established, and nothing suggests it somehow stops at the tropics. -Stefan]

  40. 40

    They say a picture is worth a thousand words, but I will try to create this cartoon with rather less. Imagine a large snowball on a slope. It represents the earth science establishment united by a system of peer review, and labelled IPCC. Further up the slope on the right, both physically and politically, stand the sceptics trying to push the snowball downhill. Below the snowball and on the left is me, a greenie, trying to push the snowball back up the hill. The slope is calibrated with increasing time along the x-axis and temperature up the y-axis. This means that the edge of the snowball can be read off against the axes to give a range of times and increases in temperature for a doubling of CO2. In that cartoon, I seem vulnerable to the danger of being crushed by the IPCC as it is pushed by the vast host sceptics, but fear not, there is so much momentum in the snowball that those pushing it from the right are having little effect. Although I am well outnumbered, it is not my strength that prevents the snowball moving; it is just inertia!

    So, I see myself as an outsider, and as a critic of the IPCC, but an unusual one. I believe that any effects that the other critics (sceptics) have had has been bad. They have been trying to move the argument in the wrong direction. However, they have found like me, that action equals reaction, and no matter how hard they push or how valid their arguments are, they cannot make the damn snowball budge! Hence, Lawson’s argument that the IPCC should be abolished.

    My criticisms are the same as those of the other critics, but the conclusions, which I draw, are diametrically opposite. I do not want to open old wounds in this thread, but in order to explain what I mean I will have to risk that by explaining them it may lead to a diversion into discussion of their merits. However, concrete examples are always better than abstract ramblings, so here goes.

    Take the Hockey Stick. The argument is that because temperatures are higher now than at any time in the past 1,000 years therefore global warming is anthropogenic. The standard criticism is that no, temperatures may have been higher, and it even descends into uninformed questioning of the data. My criticism is that even if temperatures are higher now, that does not prove that the warming is due to anthropogenic causes. They could well have been higher over the last 2,000 years, or 10,000 years, and they were certainly higher 100,000 years ago during the Eemian Interglacial, as is shown by the ice cores. (Incidentally as I see it, the proof that global warming is anthropogenic is that night and winter temperatures are rising faster than when the sun is shining. If the warming was natural then it must be due to the sun. Therefore, day and summer temperature would show the greatest increase.)

    Another case where I agree with the criticism but come to a different conclusion than the skeptics is with the MSUs. They argued that since the MSUs did not show the same warming as the surface then the Earth was not heating. My conclusion is that if the data does not fit the model then the model is wrong. I wonâ??t go further and discuss the Snowball’s response of adjusting the data for fear of libel charges :-)

    So, it is possible to be a global warming “believer” and yet accept the criticism. However, criticise from the right or from the left, and you still get violent opposition. The Snowball is like any group of people such as a family, clan, profession, or nation who unite and fight together against an attacker. So what to do? Well I don’t accept Lawson’s “final” solution of abolishing the IPCC. The peer review system may not be perfect but like the system of democracy, which elected him, Mrs Thatcher, and George W. Bush, it is the best system we’ve got. What is needed is that earth scientists realise that they, as Michael Crichton has pointed out, are unlike other scientists. They cannot experiment. Therefore, they must pay more attention to outside critics. They must search for the truth hidden in what they are saying, rather than dismiss their ideas out of hand on the grounds of “professional” scepticism.

    What I have done here is to take Lawson’s rather uninformed and prejudiced remarks which I have then distilled to find the truth which inspired them. Earth scientists must not be skeptics looking for the counter arguments. They should be sleuths searching for the gems of truth in the dark streets of real life.

  41. 41
    Johan Richter says:

    Here is the “curious report” from the house of lords. (here)

    [Response: I thought I had linked to it, but thanks for reminding me (the link is now in the main text too). -gavin]

  42. 42

    Re 41 – Where? I have been keen to read that Lord’s report for some time now.

  43. 43

    Re 41 again. I did a Google search and found a links to the “Second Report – The Economics of Climate Change” at

    Few of the Lords are heritary peers, most having been appointed by the Prime Minister of the day, and serve for life, rather like the US Supreme Court. But there is no scrutiny of the PM’s selection, nor is there any limit to their number. So now, Tony Blair has in effect packed the Senate with place men of his own choice. Comparing these lords with senators will become clearer when you read this oral evidence to a question from Lord Nigel Lawson, probably appointed before Blair became prime minister.

    Lord Lawson of Blaby: Are you aware that this, which has had a very profound influence on thinking, is explicitly stated in the Government’s White Paper to be based on proxy data, whatever proxy data may be, because there are no instrumental observations, they did not begin until the late 19th century, and that for these proxy data, which it says in small writing at the bottom, that the IPCC relies entirely on a study by a Professor Mann in 1998 and this has subsequently been examined and it was found that that Mr Mann got it all wrong in a rather fundamental way. Professor McKitrick, for example, has gone into this in great detail and so I believe have others. Is this something you have studied?

    Professor Robinson: I have not studied in any detail this question about whether we are in a trend or in a cycle but if you simply cover the projection part at the end of that graph with your hand you can see (it is not all that clear) what is happening. I am merely raising the question because I think it is an important issue because if we were in the warming phase going to a cooling phase, and the Government takes action on the assumption it is warming, then we are doing precisely the wrong thing presumably. So it is quite an important issue and I was really raising it as a question that might be addressed to the scientistsâ??what confidence they have that this is a genuine trend.

    [Response: I agree that this exchange is good evidence of the low level of debate at the HoL - you'd get better on sci.env! But Lawson is a Tory - hardly a Labour placeman - William]

  44. 44
    Stewart Argo says:

    My least favourite memory of Nigel Lawson’s tenure as Chancellor of the Exchequer was my mortgage doubling in an 18 month period.
    Leaving that aside, Nigel is in a fairly unique position. As an ex-Chancellor he can still command respect and media attention – but as a member of the House of Lords he has no longer has any accountability. He can therefore say anything he likes, without any fear of reprisals from the cabinet, whips, or the electorate. His current “job” will never be at risk.

  45. 45
    Eli Rabett says:

    I am not quite sure what Mr. McCall’s point is. Dr. Trenberth clearly stated that his calculations imply ~1″ of the rain that fell on New Orleans during Katrina could be attributed to the change of sea surface temperature associated with global warming since 1970. I clearly recognized that in my reply #9.

    The claim is made in the last summary slide of a presentation.

    Look at the preceeding slides. Which other statements on that last slide and the other slides is wrong. If you cannot find any then Trenberths conclusion is reasonable.

    The current Landsea/Trenberth/Emanuel discussion has been parsed by many to mean that Landsea claims that the number of hurricanes is constant, and Trenberth is claiming that their intensity should increase as global warming heats the ocean surface and these claims can both be true.

    However, if we are talking about hurricanes and not just cyclones, a certain proportion of cyclones will move up to hurricane status if Trenberth is right, and there will not only be increased wind speed, but also more hurricanes.

  46. 46
    Blair Dowden says:

    Katrina did not form in the average ocean where sea surface temperatures have indeed risen. It gained its strength in the Gulf of Mexico, where temperatures are currently high but there is no long term trend. I do not see how it is possible to link the rainfall associated with Katrina to global warming.

  47. 47


    Actually Katrina did form over waters warmed by global warming, it formed as a tropical depression #12 (formerly #10 had dissipated), from a slow moving wave, on the night of August 23, and the morning of August 24, on the Great Bahama Bank, according to my notes and my memories. I was watching these storms form all summer from those waters, and they were demonstrably the warmest water temperatures we have ever measured. Even before Katrina, we were stunned when measurements of surface waters of the deep Atlantic were in the high 80s. I watched these storms nucleate all summer out there, Franklin, then Katrina, and finally I observed TD#16 (Ophelia) point nucleate directly above my location, from a featureless flat calm trough, on Sunday, September 4th, and observed the cyclogenesis event almost immediately thereafter, directly into a tropical depression surrounding me completely, in only a few hours, and then I was subsequently battered by 30 knot winds.

    Those were extraordinarily hot times and waters out on the Bahama Bank this summer. That was the closest that I have ever observed multiple tropical cyclogenesis events. Something bad is going on out there, it will be interesting to see how next year shapes up. Sometimes these things go two years on and one year off, but there was a definite lack of Cape Verde types this year.

  48. 48
    Blair Dowden says:

    But Katrina was only a category 1 when it reached Florida, so does it matter how warm the Atlantic waters were? It became a significant storm only when it crossed the Gulf of Mexico. Since the Gulf of Mexico shows no warming trend, global warming has nothing to do with Katrina’s strength, so I do not see where Trenberth gets his one inch of rain from. The warm Atlantic may well affect other hurricanes, but we are specifically talking about Katrina here.

  49. 49


    I am just addressing the statement that you made about the formation and evolution of Katrina, which I witnessed, which was false, and then you claim some unjustified skepticism. Now you further claim there is no warming trend in the Gulf of Mexico, but provide no evidence of that claim.

    I myself find it fairly difficult to understand how unprecedented water temperatures in the southwest north atlantic basin, the caribbean sea and the gulf of mexico could *not* have contributed to the cyclogenesis and rapid evolution of many of the major hurricanes we witnessed this summer.

  50. 50
    Lynn Vincentnathan says:

    RE #37, people usually make decisions and policy on less that “beyond a resonable scientific doubt” evidence, and it’s always good to consider the worst case scenario & see what can be done to avert it. (Where are the “Be Prepared” scouts when we need them?) Since reducing GHGs, if done smartly, also saves money without reducing productivity, then there’s really no excuse not to vigoroously pursue such strategies — rather than continue subsidies to fossil fuels (which we pay for April 15th, if not at the pump or on our utility bills, or at least we pan costs & eco-harms off to future generations).

    (Your argument sort of reminds me of a relative. We had to go for a long walk, and there were ominous black clouds. I said, “Looks like it might rain. Let’s take umbrellas.” She said, “It might not rain, let’s not take them.” Well, it didn’t rain that time, but if it had she would’ve gotten soaked.)

    Is there any scientist who has irrefutable evidence and can prove with 95% confidence that GW did NOT contribute to Katrina? I rest my case.

    But even if I were to lose the Katrina case, & it’s proven to be totally natural beyond a shadow of a doubt, then we only have worse to expect in the future when GW really kicks in. Care to try for a Category 6, or would you prefer offing that light not it use?

Switch to our mobile site