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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. 51
    Blair Dowden says:

    Re #49: It is hard to give you my data because I used interactive maps. But I will try.

    1) Go to this NOAA page, and press Submit (accept the defaults).

    2) Select June to October (the hurricane season) and use the default time interval (from 1880 on).

    3) Select the area on the map that Katrina passed through in the Gulf of Mexico (I used longitude -95 to -85, latitude 28 to 24).

    The resulting map shows cycles, but no rising trend. I think the inputs are reasonable (ie. not cooked).

    I am only questioning Trenberth’s statement about Katrina. Temperatures in the Gulf are high, but in my view show no long term warming trend, and thus cannot be attributed to global warming, at least yet. If there is something I am missing I hope someone will explain it.

    I am not saying there is no global warming, or that it does not affect hurricane strength. The effect on hurricane frequency seems to be a matter of debate. But that warming is not uniform, there are parts of the globe that show no trend or a cooling trend. The relevant part of the Gulf for Katrina appears to be one of those areas. Of course, if global warming continues there will be fewer of those areas.

    Temperatures in the Caribean and Atlantic are rising, so storms in that region may well be affected by global warming.

    [Response: I think there is a misunderstanding here. We have pointed out before on this site that you cannot use a single time series for attribution of causes. A simple example: assume a uniform global warming has warmed all SST by 0.5 ºC in the whole world. Superimposed are regional natural oscillations. So in some region, you observe 1 ºC warming (half GW, half natural), while in others no warming at all (as the natural variation cancels the GW). In both cases, global warming has contributed equally (0.5 ºC) to the temperature (and hence, to turn to Trenberth’s argument, enhanced precipitation somewhat), even though in the latter case you observe no warming trend. To say that global warming has raised temperature by 0.5 ºC is based on the overall evidence for global warming, not on observing a local trend. It is reasonable to assume that the effect of global warming is smooth and large-scale, and does not stop at the Gulf of Mexico. -stefan]

  2. 52
    Steve Bloom says:

    Re #51 (BD): I’m no expert on this, but off-hand I would note that the link appears to show just sea *surface* temps. I saw it noted on a number of occasions this year that the loop current was very unusual in that it was quite deep as well as quite warm. Depth is important since one of the ways hurricanes lose energy is by churning up deeper cold water. If they just churn up more warm water, it could be expected to have the opposite effect. Also, I believe it’s the case that the loop current is the product of heating in the Caribbean.

  3. 53
    Blair Dowden says:

    Re #52: Here is a discussion of loop currents at Wikipedia. No mention of the cause of a stronger loop current. But it is a good point that sea surface temperatures do not carry information about the 3 dimensional temperature profile, which can be very important.

  4. 54


    You were questioning a result by making *false* claims about it, which I quickly corrected. For instance, we get our modern data from here :

    Just because you *think* something is true doesn’t necessarily make it so. For instance, I can hypothesize that you are Blair Dowden, president of Huntington University. This is a hypothesis that may be easily falsified.

  5. 55
    McCall says:

    re: response in post 39. Sorry if my post wasn’t clear, but you have misread my point — I agree with Professor Pielke, that the lead IPCC WG1 author has claimed a link between hurricane strength and GW. My criticism of Mr. Rabett and others was that they were denying the obvious — the presentation and particularly slide 20 were clearly constructed with exactly that linkage to be conveyed (whether the audience was technical or not)!

    I believe the courtesy afforded Professor Trenberth should also apply to Professor Landsea, and I would still like to hear from him about this presentation and particularly slide 20. It would not be a stretch to perceive Professor Trenberth’s positions in that presentation as exactly the those that contributed to Professor Landsea’s IPCC resignation.

    Again my apologies for the confusion.

  6. 56
    Ian Castles says:

    Gavin, You argue in your initial posting that “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.”

    This may be all that actually matters to you, but the simple fact of the matter is that the IPCC’s Special Report on Emissions Scenarios (SRES, 2000) is explicit that the scenarios are intended for THREE uses, and that the Panel has decided that they are suitable for all three of these uses in the AR4. The FIRST use is indeed to provide input to climate models. The SECOND use is “To provide input for assessing mitigation and adaptation possibilities, and their costs, in different regions and economic sectors”, and the THIRD use is “To provide input to negotiations of possible agreements to reduce GHG emissions” (SRES, s. 1.3, p. 64).

    You say that Lord Lawson is the victim of “a confusion between the IPCC and the policy options exemplified by the Kyoto Protocol”, and that “These are two quite separate things.” In one sense you are correct: the Royal Society (UK) and fifteen other scientific academies were certainly wrong when they issued a statement in May 2001 in which they conflated their support for the IPCC “as the world’s most reliable source of information on climate change” with their support for the ratification of the Kyoto Protocol as a “small but essential first step towards stabilising atmospheric concentrations of greenhouse gases” (HoL Committee Report, vol. 2, pps. 295, 305).

    This statement provided useful material for the former Chairman of the IPCC, Robert Watson, to use in evidence to a Committee of the Australian Parliament soon afterwards (Dr. Watson was, and remains, the Chief Scientist at the World Bank, an organisation that you describe as “not noted for its scientific expertise”. He ceased to be Chairman of the IPCC in April 2002, but still claims to hold this post in his page on the World Bank Experts website).

    However, as Lord Lawson rightly pointed out in his evidence to the US Senate Committee on the Environment and Public Works on 5 October 2005, the key question of what should be done about such global warming as may occur is not a matter for scientists. Governments would have been assisted in their assessments of mitigation and adaptation possibilities and the provision of input to negotiations of agreements such as the Kyoto Protocol and possible successors if the IPCC’s SRES had been technically sound. The UK has now remedied this deficiency by establishing an inquiry into the economics of climate change under the direction of Sir Nicholas Stern, Head of the Government Economic Service and former Chief ECONOMIST at the World Bank.

    You go on to say that “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, p. 39) – 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.” With respect, you are here disregarding three distinct issues.

    First, so far as “climate model results” are concerned, simulations using models other than the MERGE model illustrated in Table 3 of the Lords Report have shown much greater differences in TOTAL emissions arising from the mismeasurement of output than those shown in that Table. For example, the second of the papers cited in footnote 53 on p. 33 of the HoL Report found that the difference between MER and PPP-based estimates was three times as great as in the unpublished Manne and Richels (M&R) working paper that the IPCC chose to use to dismiss the Castles and Henderson critique.

    (Incidentally, I’m surprised at your claim that the IPCC makes no proclamations in between the full assessments. The IPCC’s press statement in Milan on 8 December 2003 claimed, on the basis of the unpublished M&R paper to which I’ve just referred, that “The claim of C&H, therefore, that there is an upward bias in the SRES scenarios is totally unfounded.” What is that, if it is not “a proclamation” The Lords Committee, which certainly investigated this matter more closely than the IPCC, noted that “several critiques show that predictions could be significantly affected by the use of PPP exchange rates” and that “PPP is the right procedure, as Professor Nordhaus’s study amply clarifies” (para. 72). When asked by Lord Skidelsky whether “the critics have influenced the methodology”, Dr. Pachauri, Chairman of the IPCC, said that “It only validates the methodology that the IPCC used earlier” and that “It does not require any deviation from it.” At the International Statistical Institute meeting in Sydney in April 2005, I met with scores of national accounting statisticians from all over the world. None of them believes the IPCC approach is correct. The Panel chose to use the United Nations Statistical Commission definition of GDP, but to ignore the outcome of fifty years of research into the proper procedures for aggregation. This was bad science, but the IPCC has been able to get away with it by excluding all national accounts statisticians from AR4. To the best of my knowledge, no member of the International Statistical Institute was chosen by the Working Group II and III Bureaux for the writing teams of the Contributions of these Working Groups to AR4.

    Secondly, it is important to recognise that the error in the SRES procedures is not uniform between regions. So far as emissions are concerned, the predominant effect of the use of the faulty procedure is on the aggregates for developing countries. Even if TOTAL emissions were unaffected by the use of the wrong measure of output, the SRES projections of REGIONAL emissions would still be seriously astray. The SRES projections of regional emissions are therefore unsuitable for mitigation or adaptation analyses.

    Thirdly, the policy processes mediated through the UNFCCC and the Kyoto Protocol require estimates of output and GHG emissions per unit of output: not just the product of these two variables (emissions). Partly as a result of the failure of the SRES authors to adopt the internationally-recognised System of National Accounts, the UNFCCC monitoring processes are in a complete mess. For example, the international team of experts that conducted the review of the progress of the European Union in meeting its obligations under the Kyoto Protocol calculated GHG emissions per unit of GDP (PPP), but the international teams that conducted the Expert Reviews for some major individual countries within the EU, such as France and Germany, presented GHG emissions per unit of GDP(MER). The IPCC proclaims that this doesn’t matter because “The economy does not change by using a different metrics (PPP or MEX), in the same way that the temperature does not change if you switch from degrees Celsius to degrees Fahrenheit” (IPCC Press statement of 8 December 2003). This is of course palpable nonsense. Does any IPCC scientist think that it’s OK to compare Country A’s temperature in degrees Fahrenheit with Country B’s in degrees Celsius, and then take an average of the two, without adjustment, to get the mean temperature of the two countries taken together?

    You say that Lord Lawson’s claims that IPCC’s ‘ignoring of dissent’ is a ‘scandal’ betrays a fundamental ignorance of how the IPCC works, and that the next IPCC report “will assess the validity of any criticisms published in the scientific literature in its next report, due in 2007.” You also claim that 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.” These are your perceptions, but in the aspects of the Panel’s work with which I have personal knowledge, Lord Lawson’s perception is far closer to the truth. The IPCC has never published a report of the Expert Meeting on Emissions Scenarios at which I made a presentation, at the Panel’s invitation, in Amsterdam in January 2003. In an effort to ascertain how elementary errors escaped detection in the IPCC’s Third Assessment Report (TAR), I asked the IPCC Secretariat where I could find review comments on selected chapters that, according to the Panel’s procedures, are held in an open access archive for five years. I have never received a reply.

    Finally, I must disagree with your reference to “small and vocal minorities” complaining that they have been shut out of the IPCC process. I pointed out in my first letter to the Chairman of the IPCC in August 2002 that statements that were made in the TAR had been found to be “material errors” in a unanimous report of experts to the United Nations Statistical Commission. These experts do not represent a “small minority”: so far as I know, all national accounts experts and index number theoreticians agree with them.

    [Response: Ian, thanks for your comments. I am unable to spend any time going through the economics literature to sort out the claims of different models (maybe an Intergovernmental Economic Assessment process is required?), and I am not qualified to assess them in any case. However, in the years that you have been working on this, I am not aware of results from you demonstrating that climate modellers need to pay attention to this. In the meantime, we have run many of the IPCC scenarios while at the same time we have developed our own scenarios (albeit in a less sophisticated way than the SRES process). None of the modelling groups are locked into exclusive contracts with IPCC, so here is my challenge to you: Produce a set of scenarios (global mean CO2, CH4, N20, CFCs etc.), that correct the problem as you see it, and if they are of sufficient scientific interest (i.e. if they diverge significantly from the range of scenarios we’ve already done – see for the range we have already run), then we’ll run them as well. One can waste an awful lot of time writing letters and arguing about whether something matters, but since us modellers are basically empiricists, a practical demonstration is worth a thousand blog comments. -gavin]

  7. 57
    Roger Pielke Jr. says:

    Gavin (response to Castles #56)-

    This exchange highlights a dynamic documented (empirically) regarding scientific assessments by Cash et al. (citation and link below). Specifically to the IPCC, its champions focus on its “credibility” to the exclusion of its “legitimacy” (specific definitions below). In your reaction to Lawson and also to Castles you emphasize the credibility of the process, but this is not what either is talking about. The result is, as documented by Cash et al., risks to credibility, salience and legitimacy.

    Cash, David, Clark, William C., Alcock, Frank, Dickson, Nancy, Eckley, Noelle and Jager, Jill, “Salience, Credibility, Legitimacy and Boundaries: Linking Research, Assessment and Decision Making” (November 2002). KSG Working Papers Series RWP02-046.

    Here are some definitions from Cash et al.:

    “Legitimacy refers to whether an actor perceives the process in a system as unbiased and meeting standards of political and procedural fairness. Legitimacy involves the belief that S&T systems are “fair” and consider appropriate values, interests, concerns, and specific circumstances from multiple perspectives. Audiences judge legitimacy based on who participated and who did not, the processes for making those choices, and how information is produced, vetted, and disseminated.”

    “Credibility refers to whether an actor perceives information as meeting standards of scientific plausibility and technical adequacy. Sources of knowledge must be deemed trustworthy and/or believable, along with the facts, theories, and causal explanations invoked by these sources.”

    Here is what Cash et al. say about how the IPCC has tended to focus on credibility to the exclusion of legitimacy and salience. (My interpretation is that legitimacy has more to do with politics and salience with policy.) Their argument is that it is counter-productive to try to build a wall around credibility, even though there are incentives to do so.

    “Traditionally, scientists, managers and scholars of science, technology and policy have focused on credibility – how to create authoritative, believable, and trusted information (Price 1965; Wildavsky 1987). For example, during the creation of such bodies as the Intergovernmental Panel on Climate Change (IPCC), priority was given to creating organizational structures that assure credibility of the information being produced – through peer review, rigorous vetting of participants, etc. (Agrawala 1998). Recent research and practice, however, point to the danger of overestimating the importance of credibility alone, while undervaluing two other attributes of science and technology systems: salience (how relevant information is to decision making bodies or publics) and legitimacy (how “fair” an information producing process is and whether it considers appropriate values, concerns, and perspectives of different actors.)”

    You simply cannot address concerns about legitimacy by reverting to exhortations of credibility. Lawson and Castles are primarily raising issues of legitimacy. This is why it matters when people write letters, author blogs and generally seek to determine what matters for political and policy discourse. When science encounters society you can expect that science will have to adapt to the realities of policy and politics, and not vice versa. Of course, if the science issues are not relevant for decision makers or the public, most of this is moot. All of this is to say, for a scientific assessment to be successful (whether a UN IPCC or group weblog) it will have to pay attention to legitimacy and salience in addition to credibility.

    [Response: Fair enough, yet what has happened is that people who don’t want the process to be credible, instead focus on legitimacy as their criticism, and so as in the ‘scientization’ of policy debate, you see a ‘legitimization’ (to coin a term) of the credibility argument. As is clear, this argument has more traction, and so is being favored by many different actors. Since the real argument is not about ‘legitimacy’ at all, but about the credibility of the conclusions, it is pointless to get engaged on the legitimacy question. It just ends up being a distraction (which is of course the point of the criticism in the first place). – gavin]

  8. 58
    mike says:

    IPCC should win, whatever

  9. 59
    Dan Allan says:


    I think it should be acknowledged that there are many critics of the process who simply want AGW to not exist, and will criticize regardless of how well the process is perfected. How far should one bend then in the hopes of gaining “legitimacy” with these people, when we basically know ahead of time that this is futile?

    In other words, one needs to define legimitacy in such a way that it is possible to achieve.

  10. 60
    Roger Pielke Jr. says:

    Gavin (reponse to #57) and Dan (#59)-

    To succeed, the IPCC needs all three of legitimacy, credibility and salience. For example, as I have discussed on our blog, legitimacy is risked when the IPCC leadership engages in political advocacy. Legitimacy is also risked when the IPCC reacts very negatively to complaints such as those leveled by Castles/Henderson and Landsea. Salience is risked when the IPCC uses different definitions of “climate change” across its three reports. These are but a few examples of issues which the IPCC could pay closer attention to. The overriding focus on credibility comes at a cost. I disagree with gavin that issues of legitimacy are just a distraction. They are very real. Lawson’s essay is a good example. By the way, this argument on legitimacy, saliency, credibility is based on a well-developed perspective from the GEA project at Harvard led by Bill Clark. At a minimum worth thinking about carefully.

  11. 61
    Gerald Machnee says:

    Re # 50
    Your first paragraph has nothing to do with the discussion. If you want to “Be prepared’, you prepare – ie, do not build below sea level, do not build on fault lines, have stockpiles of supplies available for disasters (a lesson not learned beforehand for New Orleans). You do not need to debate whether GW caused the problem – it is called – ” Be ready”. You just want to get your “religion” into every discussion.
    ***(Your argument sort of reminds me of a relative. ***
    This preceding statement is the same as your AGW comments about hurricanes. You make them with no scientific evidence. You know nothing about me, and hurricanes are not your expertise.
    A couple of comments will suffice – a) I do not own an SUV, b) I have been preparing and conserving for a long time. I was 25 years ahead in insulating my house to above standards and thereby conserving heating energy supplies.

    ***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.***
    This is a meaningless statement you should think about. I have already indicated that competent scientists have said that it is impossible to attribute how much GW contributes to the INTENSITY of hurricanes (some have indicated 5-10 percent). But I can say that we are more than 95 percent certain what CAUSES hurricanes to originally develop. And I am quoting competent research. So my comments still apply – do not make statements about GW causing most of a hurricane unless YOU have proof.

  12. 62
    Brooks Hurd says:


    Do you really believe that all criticism, regardless of its basis, is a distraction?

    No person is correct 100% of the time. The same holds true for an organization. Errors are made because it is human to err. When a person or an organization makes an error, the most important thing that can happen is for that person or organization to recognize that an error occurred and to discover why the error was made. Knowledge of what happened allows learning from the error.

    Only after you recognize what happened and correct it can a person or organization put controls in place which serve to prevent such errors from re-occurring.

    [Response: Of course not. People involved in IPCC as in all other domains make mistakes and incorrect decisions. Don’t mistake my criticism of specific (spurious) arguments for a claim of general perfection. For instance, I think it would have been useful to attach subjective probabilities to the different scenarios – I understand the reasons why they weren’t, but still… There are other minor issues that I’ve had with the process, but they don’t come anywhere near justifying shutting the process down. To paraphrase Churchill (I think) – the IPCC is a terrible idea, except for all the others. -gavin]

  13. 63
    Ian Castles says:

    Gavin, Thank you for your response to #56. In saying that “what balance between adaptation … and mitigation … is likely to be more cost effective is not a question within the remit of the IPCC”, you are essentially agreeing with Lord Lawson’s statement to the US Senate Committee on Environment and Public Works 5 October that the key question of what should be done about such global warming as may occur “is not a matter for scientists at all.” I agree. However, in answering that question the world’s governments depend (excessively, in the view of Lord Lawson and many others, including me) upon the assessments of the intergovernmental panel that they have set up for the purpose. With the support of around 200 governments, and with the science academies of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden and the UK proclaiming that they “recognise the IPCC as the world’s most reliable source of information on climate change and its causes” and endorse its method of achieving consensus, I see little point in Ian Castles asking GISS to produce a different assessments of the outlook for emissions, forcings and temperature change.

    You say that a 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.” Sorry, but I don’t believe the point IS worth making, or that it’s even correct. The costs that the world bears to get to any defined target are incurred ex ante. They are the costs that are BELIEVED to be necessary to get to the specified level, and these depend in turn upon the IPCC projections of future emissions profiles, concentrations of GHGs, forcings and temperature change in the absence of policies that explicitly address climate change. What Lawson “really feels” is irrelevant, as are the assessments of Ian Castles or David Henderson or James Hansen. Governments are spending billions (and committing themselves to trillions) because they are constantly being told that the threat of climate change calls for urgent and drastic action. We won’t be able to get our money back if it turns out that the IPCC “without climate change policies” projections were overstated and we could have had ‘Kyoto for free’.

    You have challenged me to “produce a set of scenarios (global mean CO2, CH4, N2O, CFCs etc.) that correct the problem as you see it, and if they are of sufficient scientific interest (i.e., if they diverge significantly from the range of scenarios WE’VE already done …), then WE’LL run them as well” (EMPHASIS added). This misses the point. Governments aren’t interested in Ian Castles’ scenarios or GISS scenarios: they are relying on the IPCC scenarios: the Panel has determined that these “provide a credible and sound set of projections, appropriate for use in AR4”.

    I am puzzled by your comment that “In the years that you [i.e., me] have been on this, I am not aware of results from you demonstrating that climate modellers need to pay attention to this.” I’m not sure what you mean by “this”, but let me give an example of the kinds of questions that I have been raising. In my presentation to the IPCC Expert Meeting in Amsterdam in January 2003, I said:

    ‘In his very interesting paper in the session “The SRES scenarios and application in climate research” on Wednesday afternoon, Dr. Tom Wigley identified the A2G IMAGE and the B1T MESSAGE scenarios as “the extreme scenarios in terms of the 2100 forcing pattern”. He noted that the A2 IMAGE scenario projected a burden of 780 ppm [equivalent] CO2 in 2100, whereas the B1T MESSAGE scenario projected a burden of 480 ppm. And he described these extremes as capturing “the total range of possible variation” ‘.

    I went on to question whether the B1T MESSAGE scenario DID capture the low end of the range of possible variation. I noted, for example, that this scenario assumed faster economic growth in the developing countries in the medium term than the highest of three scenarios being considered by the World Bank in its monitoring of progress towards the Millennium Development Goals. In a supplementary paper, I listed eight reasons why B1T MESSAGE might overstate emissions – e.g., that this scenario assumed a 44 per cent growth in global CH4 emissions between 2000 and 2050, whereas it was stated in James Hansen (ed.), “Proceedings of a Workshop on Air Pollution as a Climate Forcing” that “Such efforts [to contain methane emissions for non-climate-policy reasons], if international, will clearly stabilise methane abundances, avoiding the large increases projected in some of the SRES scenarios.” If I were writing now, I could add more points – e.g. that under the International Energy Agency’s “Alternative Scenario”, which “considers those policies that countries are currently considering or might reasonably be expected to adopt taking account of technical and cost factors, the political context and market barriers”, annual CO2 emissions from fuel combustion in 2030 will be lower than under ANY of the 35 SRES scenarios (IEA, International Energy Outlook 2004).

    The Australian Government apparently thought that I had a point, because in its submission to the IPCC on the scoping of AR4 (March 2003) it suggested that the Panel “consider whether there are plausible emissions scenarios outside the range indicated in the SRES and if so, manage integration of such scenarios into the AR4 (for example, consider developing a further scenario with lower developing country growth than the B1 scenarios, but without the high population and slow rate of technology growth associated with the A2 and B2 scenarios).” But the IPCC decided, in its wisdom, that the set of scenarios developed in the late 1990s were appropriate for use in AR4 and that no new scenarios would be developed.

    No respectable business enterprise would use ten-year-old forecasts as a basis for developing its long-term plans, and I’m concerned that governments, many of whom believe that climate change is the greatest challenge facing the planet, seem content to rely on projections which are already running well ahead of actual outcomes.

    Thanks for the offer to run my alternative scenarios, but I don’t see the point: it would only be a Castles/GISS scenario, not an IPCC one. The Australian Government could have asked CSIRO to run off the scenario that I suggested in Amsterdam as soon as the IPCC decided to rely on the SRES set for AR4, but what would that have achieved? The result would have been an Australian scenario and, as you said in your initial post, “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.”

    In my paper “The role of the IPCC is to assess climate change not advocate Kyoto” (available at ), I drew attention to the paper “A Brighter Future” (Climatic Change, 2002, 52: 435-440) in which James Hansen explicitly rejected the claim that the actions needed to avoid a “gloom and doom scenario” in climate change were “economically wrenching”. He argued that, on the contrary, these actions “made sense independent of global warming”. He was critical of “the IPCC predilection for exaggerated growth rates of population, energy intensity and pollution”, and of its “failure to emphasise data”, and gave a number of reasons for believing that the IPCC scenarios were “unduly pessimistic”. He questioned whether these scenarios were necessary or even plausible, and contended that “global warming can be slowed, and stopped, with practical actions that yield a cleaner healthier atmosphere”. He argued that the focus of international action, at least in the short run, should be directed towards the reduction of air pollution through concerted efforts to develop and share clean technologies. He contended that “this approach would unite the interests of developed and developing countries, and that the benefits (not least in the saving of human lives) would accrue immediately rather than in 100 years.”

    I’m surprised that you claim that 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 and that “These are two quite separate things.” James Hansen said in his appearance before a US Senate Committee in May 2001 that “the real problem is probably the close binding between the IPCC and the Kyoto Protocol discussions”; that “Kyoto excludes consideration of air pollution (such as tropospheric ozone and black carbon), for example, so IPCC basically ignores these topics and downgrades them”; and that “the only IPCC ‘review’ of our paper [canvassing the Hansen alternative scenario] was by the IPCC leaders … who saw our paper as potentially harmful to Kyoto discussions.” I don’t read Hansen’s evidence as saying that the IPCC and Kyoto are two quite separate things: on the contrary, he argued that the close links between these things had inhibited examination of the Hansen alternative (and he implied that his difficulty in publishing his paper in ‘Nature’ could be attributed to the same close linkage). I don’t believe that James Hansen was confused on this matter in 2001, and I don’t believe that Lord Lawson is confused in 2005.

    In my April 2004 paper (link provided above) I concluded that:

    “I am not competent to assess the full implications of Hansen’s ‘alternative scenario’. But it is a matter of public record that, four years after its publication, this radical proposal, which – if valid – has far-reaching implications for the appropriate policy response to the prospect of global climate change in the coming decades, has not been considered by the IPCC … The IPCC’s failure to consider the Hansen ‘alternative scenario’ and its dismissal of the Castles and Henderson critique are disturbing signs that the Panel’s role in the assessment of the science of climate change has now become subservient to its role in supporting a specific policy agenda.”

    That remains my view. However, the Australian Government’s view has become much more alarmist. According to a recent news report, Australia’s Environment Minister, Senator Ian Campbell, told a reporter that:

    “If we’re to avoid getting to 550 parts per million [CO2 concentration], you need a massive injection of new technology, you need basically everything the world’s got at its doorstep at the moment. You need wind, solar, nuclear, gasification of coal, you need every single thing and you need more” (Matt Price, “Debate over, it’s time to save planet”, The Australian, 27 October 2005, p. 1).

    Obviously Australia’s Minister and James Hansen can’t both be right. The Minister says that in order to avoid getting to 550 ppm it will be necessary to do a whole range of things that would not be considered other than for climate policy reasons (e.g. gasification of coal, rapid expansion of nuclear energy). By contrast, the ‘alternative scenario’ in Hansen’s 2002 paper implied that a stabilisation level well below 550 ppm could be achieved with actions that “made sense independent of global warming.” According to Hansen, the latter approach would yield immediate benefits, including the saving of human lives, whereas much of the benefit of the former approach would not be realised for 100 years.

    You concluded your comment on my earlier note with the observation that “One can waste an awful lot of time writing letters and arguing about whether something matters, but since us modellers are basically empiricists, a practical demonstration is worth a thousand blog comments.” Could I suggest that you are better placed than I am to make that practical demonstration? Obviously it matters a great deal whether the world has to make large sacrifices to meet the challenge of climate change, as Australia’s Minister for the Environment believes; or whether, as James Hansen argued in 2002, we can have “A Brighter World” by doing things that make sense independent of global warming.

    The GISS ‘Alternative Scenario’ (AS) to which you provided a link appears to have CO2 concentrations stabilising at 475 ppm in 2100. This seems to be around the same as the lower extreme of Tom Wigley’s lower bound of possible variation, as represented by B1T MESSAGE. Is it possible to make any comparisons between B1T MESSAGE and the GISS AS in terms of what is being assumed? For example, B1T MESSAGE assumes that 30 per cent of the world’s energy supply will still be being met from fossil fuel sources in 2100. Many technology futurists are surprised to hear this and believe that the proportion is more likely to be nil. What does the GISS AS assume about the growth of renewables and nuclear energy (the IEA Alternative Scenario mentioned above does not assume any great expansion in energy from these sources by 2030)? What about the gasification of coal, which Senator Campbell believes is needed even to achieve 550 ppm? I realise that these are difficult questions, but the difference between the Minister’s implied projection and the GISS AS is so great that it must surely be possible to say something about the reasons for the difference. This is central to the whole debate.

    Finally, I don’t think that there should be a separate Intergovernmental Economic Assessment process. Economic assessments are a vital element in projections of emissions. The main change required, as David Henderson and I have argued in our paper “International Comparisons of GDP: Issues of Theory and Practice” (“World Economics”, Jan-Mar 2005) is ‘agreement on the basic point that international comparisons of GDP do not yield differences in output: to measure such differences, prices have to be directly compared, and PPP converters estimated accordingly.” If you are “unable to spend any time going through the economics literature to sort out the claims of different models”, you could at least try to ensure that GISS gives no more support to the absurd downscaled GDP database published on the CIESIN website at As I pointed out in my presentation at Amsterdam, these estimates are worse than useless and can only ‘encourage researchers to base their work on faulty data and to reach unsound conclusions.’ Even the IPCC now recognises that these data are inconsistent with the SRES storylines. At the IPCC Bureau meeting in New Delhi in 2004, it was decided that “If researchers would like to use the downscaled data from CIESIN they can do so, but it has to be clear that IPCC does not endorse or recommend them …” (Report, para. 3.4). In other words, the projections are all wrong, but the IPCC is not prepared to prohibit their use because they have already been widely used in papers by lead authors of the Working Group II Contribution to AR4. The continued dissemination of this material by CIESIN reflects poorly on the Earth Institute at Columbia University – and the Director of the Institute, the economist Jeffrey Sachs, has added insult to injury by saying that “having climate scientists at the table to highlight the shortcomings of grossly simplified economic models is invaluable for arriving at proper policy conclusions” (quoted in Royal Society Submission to the HoL Committee Inquiry, vol. II, p. 294). Having climate scientists at the table is indeed invaluable, but it is equally important to ensure that valid data is used in the economic models that are equally essential for arriving at proper policy conclusions.

    [Response: Your failure to produce your own scenario is disappointing. Without one, it will look like you’re just barracking from the sidelines. There would be no need to run a model with your scenario(s) – the point would be to see how different your scenarios are from the current range. The suspicion remains that the answer is, they wouldn’t differ much – William]

    [Response: I’ll make two points. First, please keep your comments brief. Second, you know as well as I do that the difference between the alternative scenario and the SRES scenarios is that the AS considers that efforts will be made to reduce emissions, while the SRES scenarios explicitly don’t. AS is therefore a test of what we may be able to get away with, while SRES and similar are tests of where we could end up if nothing were done. -gavin]

  14. 64
    Ian Castles says:

    William, I do not have any capacity to produce my own scenarios: I have devoted most of my own time for the past five years to reviewing and critising the economic and statistical reporting of the United Nations Development Programme, the World Bank, the Millennium Ecosystem Assessment, the United Nations Environmental Programme, the International Energy Agency, the US Energy Information Administration and the IPCC.

    My critique of the IPCC scenarios, in collaboration with David Henderson, is itself only a part of my wider criticism of the IPCC’s economic and statistical work. Several of the agencies listed above (most notably the UNDP and the US EIA) have welcomed my comments and have greatly improved the quality of their statistical reporting. They have acknowledged my assistance both privately and, in the case of the US EIA, in its publication “International Energy Outlook 2005”. In contrast, the IPCC has refused to admit error: in fact the Panel issued a press statement (its only press statement in a period of more than two years) which was specifically and exclusively devoted to brushing aside our critique.

    I have received no remuneration for any of this work from any source. I pay for my computer, my internet access, my stationery and my telephone bills from my own pocket. I prepared a set of charts for the technical meetings on the IPCC scenarios which I attended, at the Panel’s invitation, in early-January 2003. These were attached to a draft agreed report on the discussions which was provided to the Chairman of the IPCC, Dr. Pachauri, but which Dr. Pachauri has declined to release. The IPCC has not released any report on the Expert Meeting in Amsterdam in January 2003, which was attended by more than 50 experts from around the world.

    You say that “without [my own scenario], it will look like you’re just barracking from the sidelines.” It may look like that to you, but the unanimous view of an all-Party Committee of the House of Lords (including former Treasury Ministers from both sides of British politics) was that, by raising the issue of the IPCC’s scenarios, Professor Henderson and I had “helped to generate a valuable literature that calls into question a whole series of issues relating to the IPCC SRES, not just the issue of MER versus PPP.”

    Your statement that “The suspicion remains that the answer is, they (my scenarios) wouldn’t differ much [from the current range]” shows that you have misunderstood the point of my posting. I didn’t suggest that they would differ much. In fact, I said in my presentation to the IPCC Expert Meeting that “Some of these variants [that I was suggesting should be explored] would probably yield a model with a lower forcing pattern in 2100 than that of B1T MESSAGE, although it is impossible to be more specific until the detailed modelling work is done.” The IPCC’s failure to explore the Australian Government’s proposal that it develop a scenario along the lines that I had suggested is itself revealing.

    The point of my previous message was that the emissions profile in the GISS alternative scenario is FAR LOWER than the lowest of the IPCC scenarios. It is therefore reasonable to ask about the underlying assumptions, and whether they are plausible. James Hansen said that the IPCC was “lethargic” in not examining his Alternative Scenario: was that barracking from the sidelines? Do you agree that it reflects upon the IPCC that the base year for all of the scenarios is 1990, when they are being used in a report to be published in 2007 which will remain current until AR5 is published in about 2012?

    [Response: It would of course be nice for things to updated in a timely manner. But as your comment demonstrates, the ‘big picture’ is not going to depend very much on the details of the scenarios. Given that there are huge uncertainties in all such forecasting efforts, it is more useful to use them to bracket possible changes rather than try and get each one to be exactly right. Such efforts are probably useful, but they aren’t going to make much difference in the end. The bigger scientific issue are the natural feedbacks in the system that might make the CH4, O3 or aerosol forcings significantly different from those estimated solely by changes in anthro. emissions. -gavin]

    [Response: Ian – I think you’ve pretty well confirmed everything I said: you *are* just barracking from the sidelines (unlike Hansen, who is clearly involved with the scientifc work). Leaning on the House of Lords committee for support is feeble: the HoL did a pretty poor job. If your scenarios (were you to actually bother to produce one), after all this complaining, are really no different from the existing spread, then all this complaining is a waste of time. Perhaps if you spent less time complaining you’d find the time to produce a scenario – William]

  15. 65
    Eli Rabett says:

    Allow me, in my usual pleasant way, disagree with everyone. While the range of IPCC emission scenerios pretty much bracket the possible and are as good as we need for climate models, the need for better ones has much more to do with the future tax, social and industrial policies. Putting more effort into them is probably not worth the payoff we would get WRT climate studies alone.

  16. 66
    Lynn Vincentnathan says:

    RE #63, I disagree about having a separate “Intergovernmental Economic Assessment process,” unless other considerations, such as life & health and eco-valuing the earth are put on an equal footing. I have no faith in a panel composed only of economists. For me, at least, life is a more important consideration than wealth, and neoclassical economists, who reduce all biota, nutrients, the ecosystem, the nonorganic world and all other things that keep us alive to monetary value could steer us in a very wrong direction.

    This is just an idea I had. Instead of money, why not use “life years” as a standard. So, it becomes what is the best way to maximize life years (figuring those alive today, and future generations, perhaps up to 100,000 years from now, when the last of our CO2 emissions of today have finally left the atmosphere – acc. to David Archer’s post )

  17. 67
    Ian Castles says:

    Gavin, Thank you for your comments on #63 and #64. On #63, Nebojsa Nakicenovic, Coordinating Lead Author of the IPCC SRES, told the IPCC Expert Meeting on Emissions Scenarios in Washington, DC in January 2005 that “The concept of ‘non-intervention’ reference scenarios is increasingly becoming elusive and hypothetical as climate policies are becoming a reality in many parts of the world” (Report, p. 3). I agree. Moreover, on presently available information, there is no way of knowing whether the GISS Alternative scenario or the “Australian” non-intervention scenario achieves stabilisation of GHG concentrations at a lower level.

    That is because we don’t KNOW the details of the GISS scenarios (because, as I understand it, they don’t include projections of global or regional population, output, energy mix or land use changes). We have SOME of these details for the IPCC scenarios, but as William Nordhaus of Yale has noted, the SRES used “categorically the wrong procedure for aggregating world income” (HoL Report, para. 65). By contrast, the IEA Alternative Scenario, though including only one component of GHG emissions (CO2 from fuel combustion) is fully articulated to 2030.

    Contrary to your statement, I believe the “big picture” depends hugely on the details of the scenarios. The Australian Minister believes that massive and urgent action must be taken to avoid 550 ppm CO2 equivalent being reached, the Hansen Alternative says that stabilisation can be achieved at a much lower level without taking any actions that would not make sense independently of climate change. In principle, it should be possible to identify the reasons for such radical differences. Until this is done, the scenarios are of little help to policymakers. Prompted by the compelling report by the House of Lords Committee, the British Government has now established a review of the economics of climate change to be carried out by Sir Nicholas Stern, former Chief Economist at the World Bank. Perhaps this review will succeed where the IPCC has failed.

    [Response: One point of fact. Hansen’s AS does assume significant efforts to reduce emissions for climate reasons. Some changes for instance to reduce tropospheric ozone and black carbon have significant non-climatic benefits, but in and of themselves are not sufficient. To quote “I am not suggesting that the alternative scenario can be achieved without concerted efforts to reduce anthropogenic climate forcings.” ( -gavin]

  18. 68
    Ian Castles says:

    Thanks Gavin, I accept your clarification that Hansen’s AS assumes significant efforts to reduce emissions for climate reasons. However, the problem faced by the SRES modellers was that “Distinction between scenarios that envisage strict environmental policies and those that include direct climate policies was very difficult to make, a difficulty associated with many definitional and other ambiguities”: Box TS-4, p. 46). I doubt whether they’d agree with your characterisation of the whole suite of scenarios as “tests of where we could end up IF NOTHING WERE DONE”, and they’d certainly disagree with your contentions that “the scenarios are used solely for the providing input into climate models”, and that “Therefore only the final differences in the total greenhouse gas emissions actually matter.”

  19. 69
    Dan Allan says:


    In #56 you wrote:

    “The costs that the world bears to get to any defined target are incurred ex ante. They are the costs that are BELIEVED to be necessary to get to the specified level, and these depend in turn upon the IPCC projections of future emissions profiles…”

    It strikes me that this is true only in the most unlikely of scenarios, where a government invests fully in all of its anti-AGW technology at once. In practice, the investment is almost certain to take place over a series of decades, and thus the government will have lots of time to monitor changes in fossil fuel emissions and scale back future spending on AGW avoidance if it is not warranted.

    Further, some of the ways AGW might be avoided – such incentives for consumers to buy hybrids, etc. – involve no technological investment at all, and can be scaled up and scaled down as needed.

  20. 70
    Stephen Berg says:

    Ian, in response to your statements, the American Geophysical Union has a great position statement on its website:

    I’d suggest that you read it.

  21. 71
    Ian Castles says:

    Re #69. Your point is well taken, Dan. Gavin’s “Kyoto for free, as it were” provoked me into an overstated reaction in #63 (not#56). But the fact remains that the UNFCCC/IPCC/SBSTA process (see Roger’s posting at #6) is almost unbelievably inefficient and unresponsive to new evidence as it accumulates. Around 10,000 delegates are about to meet in Montreal to solemnly review the progress of various countries towards arbitrary emissions targets fixed in all-night meetings 8 years ago, for a commitment period that ends in 7 years’ time. The countries concerned won’t know their actual emissions levels within a wide range even then, and many of them wouldn’t tell the rest of the world about it if they did. And if all governments were honest, and achieved and maintained their targets notwithstanding the electoral consequences, the effect on climate would be imperceptible.

    The current IPCC assessment is using scenarios that were finalised in the late 1990s. According to the downscaled data on the CIESIN site, one marker scenario (B1) assumes that in 2005 (this year!) average incomes in India will be higher than in China, and another (B2) assumes that in 2005 average incomes in India will have fallen to less than 40 per cent of the Chinese level. These scenarios would now be only of historical interest if it were not for the IPCC’s ex cathedra pronouncement that they are suitable for use in AR4, as a result of which hundreds of researchers are basing their assessment of climate change impacts on projections that are known to be technically unsound and in any case superseded.

    In the real world, governments and business enterprise build their forward plans upon observation and evidence of TODAY’S phenomena – not around a range of forecasts about the present which were made 5-10 years ago and which have long since been falsified by events.

    Re #70, of course I’ve read the AGU statement but I don’t see its relevance to this discussion. Stephen, I suggest that you read the papers by three Australian experts that were published earlier this year by the Academy of the Social Sciences in Australia under the title “Uncertainty and Climate Change: The Challenge for Policy.” They’re available online on the Academy’s website.

  22. 72
    Dan Allan says:

    Re #71,


    Just a few thoughts: first, some of the issues you raise re IPCC, I think, are inherent in any large human endeavor with many moving parts – a mixture of bureaucracy, science, endless melding of a variety of opinions into “concensus”, etc.. So I would probably start with a somewhat limited set of expectations, and would ask not whether the IPCC process is pure, but rather whether it is tolerable – because that is usually about the best we can expect, given the complexity of the challenge and the imperfect nature of humans. Maybe it still fails this test in your mind.

    Per Gavin’s point, if the scenarios are significantly off-track, has anyone – not just yourself – come up with an alternative set of emissions scenarios? And if not, how can we even measure the potential impact of the scenario problems you are raising? (Also, if the main problem is that the scenarios are “stale” – based on old info – how often is it realistic to recalibrate them?)

    Finally, while I agree with concerns regarding countries misrepresenting their emissions rates, etc., and might even agree (I don’t really know) that emissions targets are arbitrary, what do you see as the alternative here? Would no treaty be better? Is there not a need to address AGW? If there is a need, how then should it be addressed?

    I’d be happy to look thru any links you have on this.



  23. 73
    David H says:

    Ian Castles has pointed out that the “curious report” of our House of Lords
    was a unanimous one. Lord May was also quite flattering and, on the 10th
    November, said of it:

    “It is a question not of whether we need to bring greenhouse gases under control,
    but how. That of course is the nub of the debate and the really difficult point. It is the
    issue about which the group of distinguished economists on the committee of the noble
    Lord, Lord Wakeham, said so many good and wise things. I found it reassuring that many of
    the recommendations in that report “carbon taxes and others” resonated with
    comments made in the Royal Society’s report on economic instruments for the reduction of
    carbon dioxide emissions.

    To further understand the criticisms of the IPCC in the HoL report one might read what
    Richard Tol said in his evidence to the committee in reply to Q210.

    “From that perspective, historically, it was not a surprise that the SRES
    scenarios would at some point be criticised by eminent economists such as Henderson. It
    may have been perhaps a surprise that it took so long! Another point came to light during
    this whole debateâ??and I was at the very start of SRES, which was in 1996, and it was
    one of the most controversial debates that I have ever seen. Going back to the convergence
    assumption, from the very start onwards it was clear that the SRES team had placed itself
    under constraints of political correctness, that is to say because it is an IPCC exercise
    it has to be reviewed by all the governments in the world, and if you come up with
    scenarios in which the African countries, which are a fairly large bloc (in the
    UN) “if they do not grow fast enough, they will never approve our scenarios. So this
    is what we cannot assume” and that self-censuring was right there from the

    [Response: So… even though he didn’t like the scenarios way back in 1996 neither he nor anyone else has bothered to produce an alternative scenario? Isn’t that a bit feeble? I would also be rather cautious about taking his words at face value – William]

    As to why he was no longer involved he said in answer to Q226

    “Essentially, I am not involved in the current assessment report because I have
    not been nominated by my government, my adopted government – I am not
    German – please do not think that. Essentially in Germany, for working groups 2 and
    3, only people with close connections to the Green Party have been nominated to the
    IPCC, and that excludes me immediately.”

    Before dismissing their Lordships one might wonder else influenced our PM between the
    G8 and the Clinton meetings.

    [Response: For the economics, I have little to say. But its a shame that – having said The Committee decided to restrict the scope of its investigation to certain aspects of the economics of climate change – they didn’t stick to that, but ventured onto the science, which they didn’t understand – William]

  24. 74
    DavidH says:

    Re William’s first comment in 63, Richard Tol did not say he disliked the scenarios but they were a political compromise. Ian Castles has told us how difficult it is to get another scenario introduced.

    In the UK we have a curious system of government (and for that matter justice) in which people are actually paid and provided with resources to question and, where they see fit, vigorously oppose the official view. No such checks or balances are evident in the IPCC. Their Lordships clearly identified that on the economics and as the same system of governance applies to the science they are entitled to suggest that the same defect may exist in the science.

  25. 75
    Ian Castles says:

    What is the source of the claim that, “even though he [Richard Tol] didn’t like the scenarios way back in 1996 neither he nor anyone else has bothered to produce an alternative scenario?” (William’ interpolated comment on #73)? According to the SRES, no less than 171 sources had produced 416 scenarios in the published literature, most of which dated after 1994 (SRES, p. 348). Professor Nakicenovic told the House of Lords inquiry that “there are in the order of 600 scenarios now” (Evidence, p. 133).

    Richard Tol has published many emissions scenarios in the literature: see for example his paper “Kyoto, Efficiency and Cost-Effectiveness: Application of FUND” in the Special Issue of “The Energy Journal”: “The Costs of the Kyoto Protocol: A Multi-Model Evaluation” (1999), which includes projections of global and regional CO2 emissions from 1990-2100 for a “Business as Usual” scenario and six alternative policy scenarios (Figure 4, pps. 143-47). Professor Tol concluded that “The emission reduction targets as agreed in the Kyoto Protocol are irreconcilable with economic rationality.”

    [Response: Perhaps there are more emissions scenarios. I’ve never come across them. Do they say anything interesting (i.e., do they fall outside the SRES range?). Are any of them on the web? – William]

    William also says that he “would be rather cautious about taking his {Tol’s] words at face value.” On this, it should be noted that the Chairman of the House of Lords Committee made the following comment immediately after Professor Tol used the words that William is discinclined to accept: “You have given all those erudite comments, and they sound very convincing to me…” (Evidence, p. 72). In their unanimous report the Committee said that “In his evidence to us, Professor Tol suggested that scenarios in which limited convergence took place would be politically difficult for IPCC to contemplate” (para. 63); that “We find Profesor Tol’s analysis telling” (para. 59); that “the shortcomings in the scenarios identified by Professor Tol do further underline our call for their thourough reassessment” (para. 59); and that “political considerations should not be allowed to cloud what should be a sciedntific procedure in constructing the scenarios” (para. 72).

    [Response: The Chair’s comments make it fairly clear that he was out of his depth: which is to say, he couldn’t evaluate the evidence; the stuff about limited convergence isn’t an analysis, just an assertion. Perhaps Tol could stick to the economics and leave out the politicking? – William]

    Finally, in fairness to Professor Tol, it is worth placing on record (a) that he advised the Committee that he “was a lead author in the second assessment report and a convening lead author in an intermediate report and again a lead author in the third assessment report”; and (b) that he was one of twelve experts who made a written submission to the Committee as well as giving oral evidence. He deserves better than the gratuitous slur made by William in his interpolated comment.

    [Response: I was referring to the comments about “political correctness” that Tol was making – William]

  26. 76
    Ian Castles says:

    William, re the comments that you’ve now interpolated in my #75. Yes there are many hundreds of emissions scenarios that you haven’t come across. For an out-of-date but useful review, please see SRES, Chapter 2 (“An Overview of the Scenario Literature”). In response to your implied assumption that scenarios other than the SRES set are of no interest if they fall within the SRES range, please refer to my #56, second para. Your advice to Richard Tol to “stick to the economics and leave out the politicking” comes oddly from a working climate scientist who claims to eschew involvement “in any political or economic implications of the science” – and then volunteers his views about the “low level of debate in the House of Lords” (your interpolation at #43) and advises their Lordships to get off their bums and actually generate their own scenarios (your interpolation at #7).

    [Response: Tol is welcome to politick in his own time. But testifying to the HoL he should stick to econoics. In fact, the HoL committee should have stuck to economics, as it promised to. Re scenarios, thank for the pointer. You don’t say it explicitly, but I’m presuming that they all tend to stay within the SRES range – William]

  27. 77
    Jim Dukelow says:

    Roger Pielke Jr. wrote:

    (Comment 6) “Such reckless action with science in policy do [sic] not give friendly outsiders confidence in the IPCC process.”

    and (Comment 8 ) “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 interpretation of them, presented as fact at a policy briefing, not as hypothesis in a scientific meeting.”

    and (Comment 21) “Finally, I simply reject the notion that we have in any way mischaracterized what Trenberth has said, …”

    Let me say this about that (to quote a late and unlamented politician):

    Roger has taken a single sentence off of a slide with a title, 6 bullets, and the offending sentence, and mischaracterized the offending sentence. The bullets have three “likely”s and one “expected” and the offending sentence is clearly the conclusion of a chain of hypothetical (albeit very well founded) assumptions. Water vapor **likely** increased by 4% (which assertion follows from the Claudius-Clapeyron equation). Winds **likely** enhanced by the same order (i.e., 4%). Surface latent heat fluxes in storms **likely** increase by at least this much (labelled by Trenberth as a Research topic). Thus, moisture convergence in boundary layer goes up by 8% (1.04 squared). Corresponds to **expected** increase in rainfall and latent heat release in storms: order 8% [4% to 12%].

    And finally, the offending sentence: “**Implies** 1″ extra rain near New Orleans in Katrina.”

    I’ve been reading English for 60 years now, and describing the slide and the final sentence as **unambiguous** is perverse and **suggests** an eagerness to find something — anything — with which to beat Trenberth about the head and shoulders.

    Jim Dukelow

  28. 78
    John Monro says:

    I have enjoyed reading this thread immensely. Most of it is well above my head. Much of it seems to completely disregard previous injunctions not to engage personal asides. And, most of it seems to have nothing at all to do with the original post in regard to the august body of the House of Lords Economic Committee, and a rather old and very conservative ex-Chancellor of the Exchequer. But it’s all good stuff, and it is not too difficult to discern the seething passion under the guise of rational scientific debate.

    The problem with the report of the House of Lords Economic Committee (HLEC) and Nigel Lawson’s pronouncements, is that to read these economist’s pronouncements in regard to anthropogenic global warming is comically absurd, it produces an effect as bizarre as would be engendered by reading a critique of the Theory of Relativity by a committee of lawyers. For economists to head their second chapter “The Uncertain Science of Climate Change” is not only an obvious ploy to downplay the status of climate change science, but that it comes from representatives of a social science for whom the future always comes as a perpetual surprise, is just a bit rich.

    The HLEC considers that not enough emphasis has been placed on the positive aspects of global warming, such as the CO2 fertiliser effect, and its report contains curious debates such as those about the likelihood of people accepting lower wages in remaining areas of clement climates, and the ‘distinct amenity gains’ of Northern Europe. (This amenity might however be dependent on being able to afford to move to higher ground which, of course, will become rather more expensive, or by living in a house boat – JKM) Equally the paragraphs on ‘Adaptation vs. Mitigation’ contains the same sort of wishful thinking disguised as thoughtful consideration.

    In the chapter on ‘Forecasting Greenhouse Gas Emissions and Temperature Change’ this HLEC document may be on safer ground, the high forecasts of the IPCC do seem overgenerous. But in criticising these forecasts, they entirely neglect to acknowledge the fact that these forecasts are not worked out for the benefit of economic planning, but merely for scientific illustration, and more importantly that the lower forecasts, which the HLEC are more happy to accept, are still entirely compatible with major and destructive climate change.

    The document then goes on to examine the ‘Costs of Tackling Climate Change’. This is not the place to describe in detail the arguments presented, but when you read such quotes as “the UK research programme (into alternative energy technology) has been ‘captured’ by certain renewable energy interests” and “there is a debatable assumption about the likelihood of passive energy efficiency gains” and “it is better …… to leave the market to select the technologies” and statements such as “costs of 0.4 to 1.7% of GDP are not trivial” (relative to the possible damage of global warming, I think it is right to say these costs are trivial – what did Hurricane Katrina cost? JKM) and “the UK may have taken unilateral action to no purpose” (like the child protesting to his mother as to why he should clean his bedroom when Tony or George don’t have to clean theirs. JKM) and last, but no means least “in terms of percentages of world GNP, damage is relatively low, even for +2.5oC. The damages are not evenly spread. In general, developing countries lose more than developed economies. Some models suggest no real net damage to rich countries” is a classic of blinkered optimism and of an appalling social and moral unconcern.

    In chapter 7, “The IPCC Process”, the HLEC take parts of the IPCC reports to task. Whilst I have no doubt that some of the criticisms are valid, and in such a comprehensive document as the IPCC report there are bound to be inaccuracies and mis-statements, the whole tenor of the chapter is to endeavour to cast doubt on the whole report rather than engage in reasoned and appropriate criticism. For instance, the HLEC can’t resist taking a dig at “scientific consensus” by quoting Professor Reiter’s comment “Consensus is the stuff of politics, not science…..” (the quote continues with some reasonable, but entirely irrelevant, observations about science), a professor of tropical diseases making his personal contribution to debunking major scientific agreement on climate change. If I were to hold a glass of water in front of me, and let it go, there would be a very major scientific consensus that the glass will fall to the floor, shatter and loose a good deal of entropy. By what logic, therefore, can Professor Reiter contend that consensus only applies to politics (a naive suggestion in any case, when did politics, or economics for that matter, have a consensus about anything?)

    But to give some credit to the HLEC, the summary at the end of their document reads rather better than the body. Perhaps I should have read this first. There are at least some important admissions by the HLEC on the possible severe detrimental effects of global warming, the need for the public to be informed, the likelihood of the need for major social adjustments, and the urgent need for massive investment in research, for example, to the scale of the American endeavours to put a man on on the moon. Having said that, they also repeat many of their dubious observations, some of which I outline above.

    And what to say about Nigel Lawson? He uses so many of the fallacious arguments of the global warming sceptics that one might think he had been reading this site to learn what they are, as you have so thoroughly and clearly debunked them in your pages. This quote says it all “But the real cost of this approach is not so much dearer energy as the reduction in world economic growth. It is far from self-evident, not least for the developing world, that over the next 100 years a poorer but cooler world is to be preferred to a richer but warmer one. And why should the present and next generations sacrifice their living standards in order to benefit more distant generations, who are projected in any event to be considerably better off?” The assumptions underlying these arguments are inane, and the conclusion immoral. To assume that future generations are somehow guaranteed to be better off than we are, whatever we do to the planet, however much poison we pour in to the atmosphere, however much we deplete or damage our water resources, and however quickly we plunder its other irreplaceable assets, is breathtakingly presumptuous and overbearingly arrogant. Perhaps he should have a quiet word to a German citizen who lived in Germany before the Second World War in regard to assumptions about the future. Nigel Lawson’s own conclusion, with the alteration of one word, sums it all up nicely: “We appear to have entered a new age of unreason, which threatens to be as environmentally harmful as it is profoundly disquieting. It must not be allowed to prevail”.

    But the basic problem about the argument “Climate Change vs Economic Cost” is that there can never be any meaningful answer. We are measuring two entirely different things, in other words there is no set of scales, no ruler or set of measurements that can encompass a rational comparison between the two. Climate change is a scientific issue, which will be described and answered by entirely scientific means, economics is a social science which, whilst is uses a good deal of maths and statistics, is basically the study of human behaviour as it impacts on a very narrow field of human existence. At a fundamental level the two studies have no common ground. And at a fundamental level, we, as a human species, are going to have to accept the science, which will bear ever more heavily on us, whether we like it or not, and to hell with the economics. After all, the science of global warming is nothing more than the laws of nature. Mankind has no option but to obey the laws of nature. Mankind may temporarily postpone them, like a levee against the floods, but the laws of nature are not to be gainsaid, they will, eventually, have their own way. There are no separate rules for mankind, despite economists’ quest to find them. Our choice is not between economics and science, but between a tolerable future, or no future.

  29. 79
    Ian Castles says:

    John Monro, You argue (#76) that “For economists to head their second chapter ‘The Uncertain Science of Climate Change’ is … an obvious ploy to downplay the status of climate change science.”

    It is not obvious to me. In his attack on Bjorn Lomborg’s “The Skeptical Environmentalist” in “Scientific American” (January 2002), Stephen Schneider wrote that ‘uncertainties so infuse the issue of climate change that it is still impossible to rule out either mild or catastrophic outcomes’ and that ‘uncertainties are … endemic in these complex problems that suffer from missing data, incomplete theory and nonlinear interactions.’ And in a paper published earlier this year by the Academy of the Social Sciences in Australia, Dr John Zillman, one of the world’s most eminent meteorologists and a strong supporter of the IPCC, wrote that:

    “The uncertainties surrounding climate (and especially climate change) are not limited to what will happen in the future but span the complete spectrum from our knowledge of past climate; and our understanding of the mechanisms of present-day climate; to our ability to predict the future climate. An in-depth understanding of the nature and significance of these uncertainties is essential for the formulation of properly informed national and international action on the greenhouse issue” (‘Uncertainty in the Science of Climate Change’, in ‘Uncertainty and Climate Change: The Challenge for Policy’, ASSA Occasional Paper 2/2005, available at ).

    Stephen Schneider and John Zillman have both been leading contributors to past IPCC reports and have leading roles in AR4. As neither of these leading scientists has been accused of attempting ‘to downplay the status of climate change science’, I don’t understand why you have levelled this accusation at the House of Lords Committee.

    I’m also puzzled by your reference to the ‘important admissions’ in the summary to the report, as a result of which you believe that ‘the summary’ reads rather better than the body. Presumably you are referring to ‘Chapter 9 – Conclusions and Recommendations’, which simply reproduces, word for word, the passages in the main text which are printed in bold. There are no conclusions or recommendations which have not already been reached or made, in context, in the body of the report.

  30. 80
    Dan Allan says:


    I was hoping you might address the questions I raised in post 72, but if there are too many, I will distill it a bit:

    What do you think the world should be doing, given the state of cimate science? No mitigation at all? No treaty? A different treaty? What if, in your mind, the higher-end warming estimates became more certain? Would you then favor governmental action? Or would you still oppose it?

  31. 81
    John Monro says:

    To Ian

    Thanks for your comments

    1) I did err in treating the summary as something different from the main text. Of course you are right, it is all there in the body of the report, but laid out as they were in the summary, without all the surrounding asides, it was more obvious to me that there were some useful admissions in regard to global warming

    2) In regard to the heading “The Uncertain Science of Climate Change” I don’t quite agree with your comment. Certainly working out what will happen with anthropogenic global warming is fraught with difficulty and uncertainty. It might well be impossible, as of now, to decide whether AGW will be a mild inconvenience, or a truly revolutionary and destructive force. I think you are a climate scientist? I am just an interested layperson, a general medical practitioner. When you read the heading “The Uncertain Science of Global Warming” you think, yes, that’s true and I can’t argue with it, AGW certainly is real, but the exact prognosis, that’s a tough one. In fact, as a scientist, you can’t help but give me a very detailed and thoughtful response, with references. But, when I, and I believe countless of other laypeople read this heading, I read “Global Warming, is that real or not, even the scientists are uncertain?” and it is difficult to construe any other meaning. In my sample of one layperson that was how the heading was read (my wife!)

    This very site exists precisely because large numbers of climate scientists have become so unhappy with the misrepresentation of the undoubted uncertainties of global warming science as implying equal uncertainties about the very existence of global warming. But I am given to understand by my reading in this site, and elsewhere, that there is hardly a single climate scientist anywhere who does not now acknowledge anthropogenic global warming. And indeed there are many postings to this site making the same complaint about the distortions and half truths on climate science from self-interested parties.

    I am perfectly convinced that this heading was written the way it was to mislead. Why not write something like “The Uncertainties about the Severity of Global Warming” or “The Science Debate on the Effects of Global Warming”. This conveys a much more truthful message.

    You quote “An in-depth understanding of the nature and significance of these uncertainties is essential for the formulation of properly informed national and international action on the greenhouse issue”. I beg to differ. The last thing we need is an in-depth understanding of the nature and significance of the uncertainties surrounding the greenhouse issue. The reason is that we haven’t got time. If humanity had been conducting this experiment on a world in some parallel universe, fine. But we have to pursuade a whole world of laypeople, the ordinary laypeople, not the politicians or the business people, because that is impossible, that global warming is of paramount concern to their and their children’s future, and we have to start now. They just need to know this, is global warming real, is it a threat, could it be an overwhelming threat.? If it is, can we deal with it? When ordinary people start being frightened and start demanding that politicians and business leaders deal with these issues, you will see some action. Your quote could be taken verbatim from one of George Bush’s statements, it is exactly the sort of the thing global warming deniers and sceptics want to hear. More proof, more proof. And while we wait for the sea to lap against the White House lawns, the rest of the world will have suffered whatever consequences untrammelled global warming will have dealt it.

  32. 82
    Ian Castles says:

    Re #80. These are large questions, Dan, and they go directly to the “political or economic implications of the science” in which Real Climate will not get involved.

    Re #81. John, I am not a climate scientist. I am an economist/statistician who spent 40 years in the service of the Australian Government. In 1973 I was the main author of a paper published by the Australian Treasury which pointed to “suggestions by some scientists … that as the volume of fossil fuels consumed goes up and deforestation spreads, by the early decades of next century there might be such a rise in world temperature as to melt the polar ice caps and inundate the world’s great coastal cities.” In those days it was widely believed that annual global fossil CO2 emissions could reach 12-13 GtC by the end of the TWENTIETH century – see, for example, the MIT Report of the Study of Critical Environmental Problems (SCEP, 1970, p. 54). In the event, CO2 emissions in 2000 were barely half the level that had been projected 30 years earlier, and some of the IPCC scenarios project that, even without climate change policies, fossil CO2 emissions will never reach the level that was projected for 2000 in the MIT study in 1970. Some of these scenarios also project that CO2 concentrations will never reach double the pre-industrial level. This does not mean that the growth in the concentration of greenhouse gases in the atmosphere is not a serious problem – but the MIT Study group had urged that the implications of the build-up in CO2 should be investigated because “it could be within man’s power in the next century to increase the CO2 of the atmosphere by a factor of 4 or more.” It is debatable whether this is true, and it is certainly within man’s power to avoid such an increase, or anything like it.

    I am surprised that you believe that the unanimous report of an all-Party Committee of the House of Lords contained a heading that was “written the way it was to mislead”, and I’m surprised at what appears to be an implication of your comments that scientists should seek to frighten people rather than try to convey the “in-depth understanding” to which John Zillman referred. Scientists should “tell it like it is.” If it is “exactly what the global warming deniers and sceptics want to hear, then so be it. (Incidentally, John Zillman, the author of the quote, was a Review Editor of the Technical Summary of the IPCC Third Assessment Report and also of the chapters on the evaluation and projection of regional climate, on the detection of climate change and the attribution of causes, and on climate scenario development).

  33. 83
    Richard Tol says:

    William writes that I should “stick to the economics and leave out the politicking”. I fully agree. I’m an economist, not a politician. However, William responds to my comments about the assumptions of convergence in the SRES scenarios. Convergence here means absolute convergence of per capita income, a topic that is well within the professional domain of economists (Barro and Sala-i-Martin, 1995, Economic Growth, The MIT Press). I argued before the HoL committee that SRES had decided to ignore the latest facts and theories on economic development; and adopted an unrealistic but politically more palatable “everybody will be rich soon” stance instead.

    If one were interested in climate change alone, then the details of the underlying economic scenarios do not matter much. Emissions are the only things that count. However, if one is interested in the impacts of climate change, or in the regional breakdown of the sources of emissions, then the economic details do matter. If one adopts the Castles-Henderson alternative to SRES, then global carbon dioxide emissions in 2100 fall by 10-20%. This is small compared to the uncertainties. However, some three-quarters of this global drop in emissions comes from South and East Asia. This would considerably change the political dynamics, as China and India would have to shoulder substantially less of the burden of emission reduction. Under the same scenario, although climate change would be slower, the projected economic growth in Africa would be slower too, so that poverty-driven but climate-sensitive diseases such as diarrhoea would be more prevalent in the future, and the impacts of climate change may well be higher.

    Finally, I do have my own, much ignored scenario of future development and emissions. Nowadays, to get a paper published, one needs to run the benchmark SRES scenarios as well. The reason that there so few alternatives to SRES, and no prominent ones, has to do with funding. Scenario development is expensive. Funding agencies are not interested because there is SRES, and the SRES in-crowd is fighting tooth-and-nail to maintain their lucrative monopoly.

    [Response: If one adopts the Castles-Henderson alternative to SRES, then global carbon dioxide emissions in 2100 fall by 10-20%. This is small compared to the uncertainties. Thanks for that information – very interesting. However, C+H don’t put it quite like that, which is not too surprising. See-also – William]