24 January 2010

What a Tangled Web We Weave


There is another important story in involving the Muir-Wood et al. 2006 paper that was misrepresented by the IPCC as showing a linkage between increasing temperatures and rising damages from extreme weather events. The Stern Review Report of the UK government also relied on that paper as the sole basis for its projections of increasing damage from extreme events. In fact as much as 40% of the Stern Reivew projections for the global costs of unmitigated climate change derive from its misuse of the Muir-Wood et al. paper.

I documented this in a peer reviewed paper published in 2007, which you can see here in PDF. In that paper I wrote:
Furthermore, the Stern Review uses the Muir-Wood et al. (2006) as the sole basis for projecting future global losses from extreme events (see Table 5.2, p. 138). This means that the Stern Review’s conclusions on the costs of future extreme events under conditions of climate change are based almost entirely on projections of future hurricane losses, which Stern projects somewhat mysteriously will increase to 1.3% of global GDP or higher. Its reliance on estimate of tropical cyclones losses is both direct and indirect. Its summary Table 5.2 on p. 138 indicates that increasing losses from hurricanes are one or two orders of magnitude larger than other losses that it has examined. . . inexplicably, the Stern Review concludes that US tropical cyclone losses will increase from 0.6% of GDP today to 1.3% of GDP under 2[degrees] of warming (Table 5.2). Yet, on page 130 the Stern Review cites Nordhaus (2007) to suggest that 2–3[degrees] of warming could double tropical cyclone losses from 0.06% of GDP (2005 losses) to 0.13% (future losses). There is no justification provided for increasing the Nordhaus (2007) values by a factor of 10. This apparent error (simply a typo?) is consistent with the Stern Review’s overstatement of future economic losses from extreme weather events more generally.
As I was preparing this post, I accessed the Stern Review Report on the archive site of the UK government to capture an image of Table 5.2. Much to my surprise I learned that since the publication of my paper, Table 5.2 has mysteriously changed! Have a look at the figures below.

The figure immediately below shows Table 5.2 as it was originally published in the Stern Review (from a web archive in PDF), and I have circled in red the order-of-magnitude error in hurricane damage that I document in my paper (the values should instead be 10 times less).

Now, have a look at the figure below which shows Table 5.2 from the Stern Review Report as it now appears on the UK government archive (PDF), look carefully at the numbers circled in red:

There is no note, no acknowledgment, nothing indicating that the estimated damage for hurricanes was modified after publication by an order of magnitude. The report was quietly changed to make the error go away. Of course, even with the Table corrected, now the Stern Review math does not add up, as the total GDP impact from USA, UK and Europe does not come anywhere close to the 1% global total for developed country impacts (based on Muir-Wood), much less the higher values suggested as possible in the report's text, underscoring a key point of my 2007 paper.

Consequently, anyone wanting to understand or replicate my analysis from the original source would no doubt be confused because evidence of the error in Table 5.2 was quietly changed after the publication of my paper. Had they noted the error it would have obviously led to questions about the implications, and ultimately the bottom line estimates of the costs of unmitigated climate change. [SEE UPDATE BELOW. THERE WAS ANOTHER POSSIBILITY I DID NOT CONSIDER.] Rather than rewrite the report, apparently, it was decided instead to rewrite history. Fixing facts to fit a policy conclusion is not a good idea for any government, but to do so with the quiet participation of leading academic advisors is doubly bad. Once again, not good.

In the comments Phil Clarke points to an FAQ page on the UK Treasury site that has this interesting admission at number 20:

20. You state the cost of US hurricanes at temperatures of 3°C above pre-industrial levels as 0.13% and 1.3% of US GDP in different places in the report. Which is correct?

The correct figure is 0.13%. There is an error in Chapter 5, pg. 139, which cites the cost as 1.3%. An Errata page will be published to cover this and any other typographical errors.

The FAQ page is now in error, as Chapter 5 no longer cites the cost as 1.3%, because, as documented above, the error has been whitewashed away. I am unaware of any Errata page (readers?), however, it is now unnecessary as the report itself has been revised post-publication. Someone coming to the report would have no reason to suspect any problem. In the comments boballab writes:
The disturbing aspect is that someone checking the points in your paper would almost certainly checked the online copy of the Stern report. With the quite change with no attribution it would cast doubt over the conclusions in your paper and make it look like you did shoddy and/or dishonest work, thus damaging your credibility with the scientific community, policymakers and the public at large.
The issue is much deeper than a typo -- you can seen in my excerpt from my paper above that I had already assumed that it was a typo. The problem is that once the typo is corrected it then reveals that the numbers presented by Stern just do not add up.


  1. Down the memory hole. Oceania has always been at war with Eastasia.

    Of course, this doesn't change the science. The science is settled. The consensus is based on the work of thousands of scientists. Oceania has always been at war with....

    I'm almost embarrassed to write in such cliched terms, but cliches are cliches because they're true.

  2. Great detective work Roger. If Stern's estimates of the costs of climate change are not affected by an order of magnitude change in his input assumptions about USA hurricane costs, then it shows how flakey the whole exercise is of putting dollar costs on anthropogenic climat echange out to the year 2200.

  3. I help out with litigation in my jobs. This is what the lawyers woufl call a "material" issue. This is an issue which goes to the basis of the report's conclusions. It is not a typo in a footnote. It calls into question the report's conclusions.

  4. Klaatu Barada Nikto! Now you see it and then it's gone!

  5. Er ... http://www.hm-treasury.gov.uk/sternreview_faqs.htm

    Number 20.

  6. Isnt it interesting that you keep more back copies of data than the warmists do? Remember how when they'd screwed up their "adjustments" of raw temperature a few years back after Steve M spotted a flaw in their figures they suddenly realised they had no backups of the originals?

    So just who are the real scientists here?

  7. Roger
    The disturbing aspect is that someone checking the points in your paper would almost certainly checked the online copy of the Stern report. With the quite change with no attribution it would cast doubt over the conclusions in your paper and make it look like you did shoddy and/or dishonest work, thus damaging your credibility with the scientific community, policymakers and the public at large.

  8. The onus must now be on the IPCC to prove what they have written is accurate, is true.

    Seems every time an IPCC report page is turned there is another and another serious mistake.

  9. -5-Phil Clarke

    Many thinks for this pointer. One of the joys of blogging is collected wisdom.

    I have updated this post accordingly. Interestingly, it looks like Stern chose to change the report rather than issue an Errata. Either way (though an errata would have been more proper from an academic standpoint), the issue lies not with a typo, but what problems are revealed once the typo is corrected.

    Thanks again!

  10. The Stern Review becomes another 'dodgy dossier'.

    This attempt at doctoring an offical UK government review should be reported to the UK's House of Commons Science and Technology Select Committee.


    attn. of the Clerk - Glenn McKee

  11. Roger,

    I see two possibilities:

    1) Stern did his calculations in good faith with bad data and the alterations on the site were done by someone who did not understand the implications of the change.

    2) Stern knew he used bad data yet knowingly released a report based on that bad data.

    I had assumed 1) until you got the pointer to the FAQ. Now I don't know. Is there any evidence that either supports or refutes 2)?

  12. Looking at the adobe properties of the file, it showed it as having been updated January 24th, 2007. Could this correction gone unnoticed for two years?

    Downloading the file and then checking the properties can sometimes be quite informative. Last summer I had 4 different versions of the Copenhagen Synthesis report. There was no notice of revision or errata for the first 2 versions, and one version appears to be a bootleg version done within Rahmstorf's organization.

    I am amazed that very significant climate science publications don't have the very minimal sort of revision control and documentation that virtually every engineer in the world uses almost automatically in order to minimize confusion on verions, changes, updates, etc.

    Slipshod procedures and general sloppiness that would not be accepted in most companies seems to be common in the climate science field.

  13. -12-Charlie

    I had been working on my paper in the fall of 2006 (There is a Prometheus post with an early version of some of the analysis in the paper from October 2006:

    I was using a downloaded version of the report and I am pretty sure that I have not looked closely at the online version since -- I would have never expected it to change.

    At the same time Richard Tol made a comment on Stern referencing my hurricane analysis and he mentioned the fact that it had been shared with Stern:

    Stern had been sent my critique in 2006 (though I never received acknowledgment), and early copies of my paper were in circulation for comments that fall. The paper itself was not formally submitted until March, 2007, though the editors had seen versions prior to that.

    Of course, the UK Government/Stern could have become aware of the typo on their own, or someone else could have pointed it out.

    However, the deeper problems in the analysis were shared in my paper, and I understand that Stern was fully aware of them in 2007.

    I assume that (1) is the case, however, once the errors were pointed out, as so often is the case, rather than fixing them out in the open, they were ignored, and not it looks like that for whatever reason tracks were covered.

    Not good however you interpret things, I think.

  14. Roger:

    Puzzling. US GDP in 2005 was approximately $12.4 trillion. Table 5.2 shows 2005 costs as a percentage of GDP at .06%, or roughly $74.4 billion. Yet Chapter 5 reports “weather related” Hurricane Katrina losses at $125 billion in 2005, or 1.2% of US GDP. Assuming it was valid, the Report also appears to suffer from simple math and posting problems, and the latest “correction” of extreme weather event losses at .13% of GDP for 3 degrees centigrade now seems understated.

  15. -14-Brian

    Those various numbers come from work by William Nordhaus, which jibes pretty well with that which I have been involved in:


  16. It is inexcusable that these numbers have been altered from those originally published in the Report without any indication that any changes have been made.

    According to the Cambridge University Press catalogue, the paperback version of “The Economics of Climate Change: the Stern Review” was published in January 2007. The book is shown as “In stock (stock level updated, 23 January 2010)”, and the price is given as 34 pounds stg in the UK, $US53 in the United States and $A99.95 in Australia. These books presumably show the percentage cost figures in question at 10 times greater than those given in the version now retained on the UK Government archive, with no errata page having been issued (as was apparently intended at the time tha the Q&As on the Treasury website were drafted), and no acknowledgement that any change has been made.

    This is astounding.

  17. -16-Ian Castles

    I am not sure, but I think that the book came out well after Jan, 2007, so I would guess that it has the changed numbers in it. If so, and there is no errata in the book, then this would further serve to muddy the issue.

  18. As a further indication of the confusion that potentially arises from the failure to "come clean" about errors, it is worth noting that the lists of references to Chapters 4, 6, 7, 9. 10, 13, 16, 18, 19 and 20 of the WGII contribution to AR4 all cite the Stern Review book, published in 2007 by Cambridge University Press Cambridge. The same is true of Chapters 9 and 11 of the WGIII Contribution to AR4.

    However, the electronic version of the Review is cited in Chapters 1, 3 and 4 of the WGIII contribution, with the access dates being given as, respectively, 28 November 2006, 1 June 2007 and 2 July 2007.

  19. You also appear to have omitted that EVERY OTHER REFERENCE in the fifth chapter that you link to uses the 0.13%. In short the 1.3% that has your panties in a bunch was clearly a typo, which has been corrected and you are misleading your readers.

    Key Messages: "Damage from hurricanes and typhoons will increase substantially from even small increases in storm severity, because they scale as the cube of windspeed or more. A 5 – 10% increase in hurricane windspeed is predicted to approximately double annual damages, resulting in total losses of 0.13% of GDP each year on average in the USA alone."

    Box 5.3: "The study did not take full account of the impacts of extreme weather events, which could be very significant (Section 6.4). Nordhaus (2006) shows that just a small increase in hurricane intensity (5 – 10%), which several models predict will occur 2 – 3°C of warming globally, could alone double costs of storm damage to around 0.13% GDP. The risks of higher temperatures, as the latest science suggests, could bring even greater damage costs, particularly given the very non-linear relationship between temperature and hurricane destructiveness (Chapter 3)."

    Pg 132 bottom: "Storms are currently the costliest weather catastrophes in the developed world and they are likely to become more powerful in the future as the oceans warm and provide more energy to fuel storms. Many of the world’s largest cities are at risk from severe windstorms - Miami alone has $900 billion worth of total capital stock at risk. Two recent studies have found that just a 5 - 10% rise in the intensity of major storms with a 3°C increase in global temperatures could approximately double the damage costs, resulting in total losses of 0.13% of GDP in the USA each year on average or insured losses of $100 – 150 billion in an extreme year (2004 prices).29 If temperatures increase by 4 or 5°C, the losses are likely to be substantially greater, because any further increase in storm intensity has an even larger impact on damage costs (convexity highlighted in Chapter 3). This effect will be magnified for the costs of extreme storms, which are expected to increase disproportionately more than the costs of an average storm. For example, Swiss Re recently estimated that in Europe the costs of a 100-year storm event could double by the 2080s with climate change ($50/€40 billion in the future compared with $25/€20 billion today), while average storm losses were estimated to increase by only 16 – 68% over the same period.30"

    FWIW, Katrina was exceptional, and the .13% is an average. Stern was following Nordhaus as the quote above shows.

  20. -19-EliRabbett

    I suggest reading the post and links again, as your complaint is easily shown to be incorrect. I highlight explicitly the incongruity of the other references in the Stern chapter and the summary Table 5.2. For instance, I state in the excerpt above from my paper in GEC:

    "Yet, on page 130 the Stern Review cites Nordhaus (2007) to suggest that 2–3[degrees] of warming could double tropical cyclone losses from 0.06% of GDP (2005 losses) to 0.13% (future losses)."

    The problem, as I write, is not the typo, which can happen to anyone (just read this blog daily and you'll find a bunch;-) but the fact that the Stern estimate of future losses based on misusing Muir-Woods is simply incompatible with the various country-level data when correctly presented in summary Table 5.2. The typo made the numbers appear to be of the same order of magnitude, when in fact they were not. Correcting the typo does not make the analysis correct, just obviously wrong.

    As I have already mentioned on this thread, the Nordhaus estimates are perfectly consistent with those I have published. There is nothing wrong with the Nordhaus analysis, the problem lies in the Stern analysis.

    None of this excuses altering a published government report quietly and without notice, after its publication and wide dissemination.

    There are many topics that we could debate. However, taking a stand on disasters and climate change is not your best choice of topics, as there is little if any ambiguity here in the literature, and the errors by IPCC and Stern are as egregious as they are obvious.

  21. The first edition, first print of the book has 0.13%.

    Narita et al. have .0007% (extratropical) and .006% (tropical). That has been peer-reviewed, though, and should therefore be ignored.

    Links at http://ideas.repec.org/e/pto90.html

  22. I'm confused, and maybe lazy too.

    Does the Stern Report end up using the 0.13% or the 1.3% figure when it adds up the dollar losses it considers likely/possible under the relevant scenario?

    ie, is it a pure typo that does not feed through into further calcs?

  23. The IPCC has form for this.

    When the SPM was released in Feb 2007 there was a table for sea level rise where the numbers simply didnt add up. This was quietly changed with no admission of any error or change.


  24. This is a particularly egregious abuse.
    It is in effect theft of tax payer funded services and data.
    It is the exact opposite of real science or ethical business practices.
    AGW theory promotion has seriously tarnished climate science, the science journal system and the credibility of the government and other review borads that were supposed to protect us from these sorts of corrupt practices and unprofessional activities.

  25. I suspect that Nicholas Stern did not have the personal input to this review that is implied by the title:

    The Cambridge Centre for Climate Change Mitigation Research or ‘4CMR’ is directed by Dr Terry Barker. Here are a few extracts from Dr. Barker's speech at that the opening of his new
    institute,(inactive link):
    "The Centre is focussed on computer modelling of mitigation, or slowing down, of climate
    change. It would be better to stop the change, but that is impossible. We are committed to
    it (sic).

    Cooperation must replace competition between nations in areas such as pricing of oil
    seen as critical to economic welfare and success. The foundering (sic) members of the Centre, all of whom are here, have backgrounds in many disciplines: economics, engineering, mathematics, physics, ecology and geography. But
    the focus of our research is the special intersection of economics and engineering
    concerned with climate change mitigation – particularly by economic policies inducing
    low-carbon technological change.

    It may seem astonishing, but the global climate models, providing governments with estimates of the costs of climate stabilisation are nearly all reliant on one year’s data.

    Astonishing indeed, how do they get away with it?

    A brief reminder of some of the comments from the Tyndall Web site re the Stern Review, (links now difficult to find):

    Terry Barker, leader of Tyndall’s CIAS programme of research (Community Integrated Assessment System) and Director of 4CMR, set up a project to conduct a meta-analysis of the literature on the costs of Greenhouse Gas (GHG) mitigation with induced technological change, funded by HM Treasury. This generated a report for the Stern Review.

    Terry Barker, Rachel Warren, Robert Nicholls and Nigel Arnell were asked for their comments on various parts of the draft Stern report. Finally Terry Barker read and edited the Modelling Costs Chapter of the Stern Review."

    Dr Barker and Tyndall had had the US in their sights for some time and this paper goes back
    to 2001:
    How high are the costs of Kyoto for the US economy?
    Terry Barker and Paul Ekins (Department of Applied Economics, University of Cambridge),
    School of Politics, International Relations and the Environment, Keele University.
    Tyndall Centre Working Paper No. 4 (4 July 2001)

    Estimates of the costs of implementing the Kyoto protocol are uncertain and most are based on assumptions that necessarily imply high costs. A selection of alternative (often more realistic) assumptions gives estimates that suggest net benefits rather than costs. One highcost estimate is from the US Energy Information Administration but it is based on a rapid
    short-term adjustment to Kyoto-type targets and the model does not include the flexibility
    mechanisms. Another high-cost (but long-term) estimate is from the Oxford model and suggests a 4% cost of US GDP by 2020 to achieve Kyoto targets without the flexible mechanisms. It is shown that this estimate is based on a wrong interpretation of the literature, a confusion of short-term with long-run costs, and a selection of worst-case assumptions and parameters. Provided policies are expected, gradual and well-designed, the costs for the US of Kyoto are likely to be insignificant.

  26. Roger,

    Seems the latest Science has an article using the same wrong interpretation. Will this ever end?

  27. I think this is a red herring.

    Table 5.2 reports two regional estimat (USA, Europe) and one global estimate.

    If the US number is 1.3%, the estimate for the Rest of World must have been 0.35-1.51% of GDP.

    If the US number is 0.13%, the estimate for the Rest of the World must have been 1.06-2.23%.

    This assumes that relative sizes of the GDPs of USA, Europe and Rest of the World stay as they were in 2005. 2.23% is therefore the upper bound.

    2.23% is consistent with the text.

    The 1.3% for the USA was just a typo.

    Table 5.2 was NOT used in the "cost-benefit analysis" of the Stern Review. It is just a loose end.

    The "cost-benefit analysis" has "catastrophic damages". The estimate is not based on Table 5.2. It is taken from Nordhaus, who had pulled it from thin air.

    In Nordhaus, "catastrophic damages" are a risk premium that should be added if one otherwise ignores uncertainties.

    In Stern, "catastrophic damages" are added to the uncertainty analysis. It thus double counts the risk.

  28. Roger,


  29. -28-Richard

    Thanks, but no.

    1. The global estimate (which in Table 5.2 is supposed to be developed countries) derives from Muir-Wood et al. (2006).

    2. The 2%/year increase 1970-2005 in Muir-Wood et al. and used by Stern (as a lower bound) is based entirely on US hurricanes.

    3. So the Nordhaus numbers and Stern global (Muir-Wood) are actually two different measures of the same thing. They are thus _not_ additive as you have suggested.

    4. At best they serve as an order of magnitude consistency check. You are correct that the 1.3% number was not used in the C?B calculations, those came from MW. However, had it been properly recorded as 0.13% there would have been a fairly obvious problem with the numbers to anyone who looked.

    5. When the typo is corrected they order-of-magnitude check fails.

    6. Stern's upper bound on global damages results from accelerating the Muir-Wood 1970-2005 trend by and additional 1% per decade (ie., the MW 2% becomes 3% after a decade, then 4% etc.). There is no basis for this.

    Finally, changing a text after publication is not allowed in scientific journals where errata and corrigenda are required. Stern should be held to similar standards.

  30. @Roger
    A closer look at Table 5.2 reveals that it does not make any sense.

    "developed" in the caption and "global" in the first column -- which is true?

    "all extreme weather" = "hurricanes" + "floods" or "all"?

    "floods" = all floods?

    Coastal floods = Wetland loss + coastal defense

    Because nothing is properly defined, I don't think you can draw any conclusion from the fact that 1.3% was changed to 0.13%, and that the "global" number stayed the same.

    Table 5.2 is not used elsewhere in the Stern Review, so this just illustrates how incredibly sloppy 23 people can be when given 18 months to produce 692 pages (a tenth of a page per person per working day)

  31. -32-Richard

    I agree that if you start with the Table it is very confusing. However, if you carefully go through the Chapter 5 text, you can follow exactly what they did, and what mistakes were made.

    I did exactly this in the following paper, and it is a bit complicated, but the mistakes are no less real:


    The typo that was corrected is symptomatic of the deeper problems. Having been changed unannounced it is just bad form. If that were all to it it would be a minor issue. In the context of the errors that lie beneath, the issue is considerably more troubling.

  32. Roger,

    I see you have taken advantage of the media frenzy around the IPCC to gain more coverage for your gripes on disaster losses. However, I’m afraid there are some serious errors in your public statements. As you know, I formerly worked with Robert Muir-Wood at Risk Management Solutions and I now work with several of the people who prepared the Stern Review, so I have had the chance to speak to them about your comments. I am providing my comments in multiple entries on your blog as it will not allow them to be all posted at once.

    First, let me clarify a few points about the Stern Review. You are quite right, and as the UK Government acknowledged, there was a typographic error in Table 5.2 of the version of the Stern Review that was published on the Government’s website in October 2006 –the increased costs, as a percentage of GDP, from US hurricanes was inaccurately printed as 1.3% and 0.6%, instead of 0.13% and 0.06%. The error was picked up by members of the team and corrected before the report was printed by Cambridge University Press for publication in January 2007. The error had not other significance for the report other than in Table 5.2. There was no conspiracy and no attempt to deceive – it was a straightforward typo which was corrected very soon after the Review appeared.

    Second, you are also right that the costs of extreme weather events globally calculated as 0.5-1.0% of GDP, and presented in Table 5.2 was based on the 2% trend published in the six-page paper by Muir-Wood, Miller and Boissonnade from the Hohenkammer workshop in 2006. However, it is completely wrong to suggest that “as much as 40% of the Stern Review projections for the global costs of unmitigated climate change derive from its misuse of the Muir-Wood et al. paper”. In fact, the modelling of the macroeconomic costs of the impacts of unabated climate change did not make use of the Muir-Wood et al. (2006) abstract – the costs were projected using the PAGE2002 integrated assessment model, as described in Chapter 6 of the Review. The PAGE2002 model drew upon three major sources of estimates of the impacts of climate change (Mendelsohn et al. (1998), Nordhaus and Boyer (2000) and Tol (2002)) – this is explained in Chapter 6 of the Review and also in this 2007 paper from ‘World Economics’ (see particularly Figure 2): http://www.occ.gov.uk/activities/stern_papers/World_Economics1.pdf

    Further, the Stern Review points out on page 170: “Extreme weather events are not fully captured in most existing IAMs; the latest science suggests that extreme events will increase in frequency and severity with climate change.” This statement references a technical paper by Rachel Warren and co-authors (including Richard Tol) which was prepared for the Review. It points out on page 5: “Most models do not take into account the influences of extreme weather events which are likely to contribute very strongly to economic impacts; however the top end of the PAGE input ranges do include them as far as the literature allows, albeit that literature on potential changes in the frequency and intensity extreme [sic] events is in its infancy”: http://www.dfld.de/Presse/PMitt/2006/061030c4.pdf

  33. You also complain that the Stern Review should not have cited the Muir-Wood et al. (2006) workshop paper because it was not peer-reviewed. The abstract of the paper states:

    “After 1970 when the global record becomes more comprehensive we find evidence of an annual upward trend for normalized losses of 2% per year that corresponds with a period of rising global temperatures. However over this same period, in some regions, including Australia, India and the Philippines normalized losses have declined. The significance of the trend in global normalized losses is dominated by the affect [sic] of the 2004 and 2005 Atlantic hurricane seasons as well as by the bias in US wealth relative to other developing regions.”

    The abstract also states:

    “What is presented here provides a short summary of the global results of this study. Full results are in course of publication also covering individual peril regions and the exploration of correlations with global temperatures.”

    As you know, these results were published in 2008 as a peer-reviewed paper by Miller, Muir-Wood and Boissonnade in the volume on ‘Climate Extremes and Society’. The paper reached the same main conclusions as the workshop presentation: “After 1970, when the global record becomes more comprehensive, we find evidence of an annual upward trend for normalized losses of 2% per year.” A sensitivity analysis revealed that there was no statistically significant trend between 1970 and 2005 if the losses from the 2004 and 2005 US hurricane seasons were removed. The paper concluded: “In sum, we found statistical evidence of an upward trend in normalized losses from 1970 through 2005 and insufficient evidence to claim a firm link between global warming and disaster losses.”

  34. The paper also noted several factors that should be taken into account when interpreting the results, including “changing vulnerability over time”. This means that losses from US hurricanes and other extreme weather events did not separate out the impacts of changing building standards between 1970 and 2005, which of course, would tend to obscure any trend towards increasing losses from an increase in hazard (ie frequency and/or intensity of weather events).

    Of course this limitation also applies to your paper with other co-authors in 2008 on normalized losses from US hurricanes, which simply states: “As strong codes have only been implemented in recent years (and in some cases vary significantly on a county-by-county basis), their effect on overall losses is unlikely to be large, but in future years efforts to improve building practices and encourage retrofit of existing structures could have a large impact on losses”. Although you dismiss any potential impact from improvements in building standards, and so do not take it into account, you will no doubt know that these standards improved after Hurricane Andrew in 1992 and their impact on reducing damage has been documented, for instance, in this report by the University of Florida: http://www.dca.state.fl.us/FBC/Hurricane_Research_Advisory_Committee/Report_SurveyProject_Gurley_62005.pdf

    It seems to me that your analysis may have missed the impact of changes in Atlantic hurricane activity on losses (such as the increase in frequency since 1995) due to reductions in vulnerability of US coastal properties. Surely, some research is required to justify the neglect of the impact of changing building standards? Certainly you would be advancing an important area if you were to investigate this issue more thoroughly.

    Similarly, your conclusion that increases in exposure and value at risk completely explain the trend in rising losses from hurricanes is not shared by other authors. For instance, this paper by Silvio Schmidt and co-authors on US hurricane losses, published last year in the journal ‘Environmental Impact Review’, concluded: “In the period 1971-2005, since the beginning of a trend towards increased intense cyclone activity, losses excluding socio-economic effects show an annual increase of 4% per annum. This increase must therefore be at least due to the impact of natural climate variability but, more likely than not, also due to anthropogenic forcings.”: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V9G-4W6FNC4-1&_user=1177143&_coverDate=11%2F30%2F2009&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1180772824&_rerunOrigin=google&_acct=C000051857&_version=1&_urlVersion=0&_userid=1177143&md5=2a2c466695839402c959b38b2ebfdcb0

    As I am sure you appreciate, it is important that public debate about climate change is well-informed with accurate information. Unfortunately, your inaccurate and misleading comments on your blog have now generated misleading coverage elsewhere. I urge you to exercise greater care in future to avoid making further mistakes similar to those I have outlined here.

    Best wishes,

    Bob Ward

  35. Hello this is great.it's great.thanks.