Select Committee on Economic Affairs Written Evidence

Memorandum by Professor Paul Reiter, Institut Pasteur; Paris



  1.  This evidence is presented to the Select Committee to provide a perspective on the role of the Intergovernmental Panel on Climate Change (IPCC) in compiling and assessing technical information.

  2.  I am a specialist in the natural history and biology of mosquitoes, the epidemiology of the diseases they transmit, and strategies for their control. My entire career, more than thirty years, has been devoted to this complex subject. My research has included malaria, filariasis, dengue, yellow fever, St Louis encephalitis and West Nile encephalitis, and has taken me to many countries in Africa, the Americas, Asia, Europe and the Pacific. I spent 21 years as a Research Scientist for the United States Centers for Disease Control and Prevention (CDC). At present, I am a Professor at the Institut Pasteur in Paris, and am responsible for a new unit of Insects and Infectious Disease.

  3.  I have been a member of the WHO Expert Advisory Committee on Vector Biology and Control since 1998, and a consultant for several WHO Scientific WorkingGroups. I have worked for the World Health Organization (WHO), the Pan American Health Organization (PAHO) and other agencies in investigations of outbreaks of mosquito-borne diseases, as well as of AIDS and Ebola haemorrhagic fever and onchocerciasis. I was a Lead Author of the Health Section of the US National Assessment of the Potential Consequences of Climate Variability and Change, and a contributory author of the IPCC Third Assessment Report (see below). I have been Chairman of the American Committee of Medical Entomology of the American Society for Tropical Medicine and Hygiene, and of several committees of other professional societies.

  4.  The comments that follow mainly deal with the Health Chapters of IPCC Working Group II (Impacts, adaptation and vulnerability) in the second and third Assessment Reports, in which mosquito-borne diseases have figured prominently. But first I need to give you some background on mosquito-borne diseases. I will use malaria as an example.

MALARIA5.  I wonder how many of your Lordships are aware of the historical significance of the Palace of Westminster? I refer to the history of malaria, not the evolution of government. Are you aware that the entire area now occupied by the Houses of Parliament was once a notoriously malarious swamp? And that until the beginning of the 20th century, "ague" (the original English word for malaria) was a cause of high morbidity and mortality in parts of the British Isles, particularly in tidal marshes such as those at Westminster? And that George Washington followed British Parliamentary precedent by also siting his government buildings in a malarious swamp! I mention this to dispel any misconception you may have that malaria is a "tropical" disease.

  6.  The ague thirteen times in Shakespeare's plays. In Shakespeare's time, William Harvey dissected cadavers of patients in St Thomas's hospital who had died of the infection. Harvey was the first to describe the changes in the consistency of the blood that result in the fatal complications caused by the infection. At the end of the 17th century, a certain William Talbor was knighted after he cured the King of an ague using a concoction of quinine he had developed in the Essex marshes. He later sold his recipe to Louis XIV, became Chevalier Talbor, and died rich and famous after curing many of the aristocrats of Europe.

  7.  All this occurred in a period—roughly from the mid-15th century to the early 18th century—that climatologists term the "Little Ice Age". Temperatures were highly variable, but generally much lower than in the period since. In winter, the sea was often frozen for many miles offshore, the King could hold parties on the frozen Thames, there are six records of Eskimos landing their kayaks in Scotland, and the Viking settlements in Iceland and Greenland became extinct.

  8.  Despite this remarkably cold period, perhaps the coldest since the last major Ice Age, malaria was what we would today call a "serious public health problem" in many parts of the British Isles, and was endemic, sometimes common throughout Europe as far north as the Baltic and northern Russia. It began to disappear from many regions of Europe, Canada and the United States as a result of multiple changes in agriculture and lifestyle that affected the breeding of the mosquito and its contact with people, but it persisted in less developed regions until the mid 20th century. In fact, the most catastrophic epidemic on record anywhere in the world occurred in the Soviet Union in the 1920s, with a peak incidence of 13 million cases per year, and 600,000 deaths. Transmission was high in many parts of Siberia, and there were 30,000 cases and 10,000 deaths due to falciparum infection (the most deadly malaria parasite) in Archangel, close to the Arctic circle. Malaria persisted in many parts of Europe until the advent of DDT. One of the last malarious countries in Europe was Holland: the WHO finally declared it malaria-free in 1970.

  9.  I hope I have convinced you that malaria is not an exclusively tropical disease, and is not limited by cold winters! Moreover, although temperature is a factor in its transmission (the parasite cannot develop in the mosquito unless temperatures are above about 15ºC), there are many other factors—most of them not associated with weather or climate—that have a much more significant role. The interaction of these factors is complex, and defies simple analysis. As one prominent malariologist put it: "Everything about malaria is so moulded and altered by local conditions that it becomes a thousand different diseases and epidemiological puzzles. Like chess, it is played with a few pieces, but is capable of an infinite variety of situations"

  10.  The same goes for all mosquito-borne diseases—that is what makes them so fascinating—and even the climatic factors defy simple analysis. Thus, in some parts of the world, transmission is mainly associated with rainy periods, whereas in others, epidemics occur during drought. In some highland areas, the transmission is highest in the warmest months, whereas in others, it is restricted to the cold season. In Holland, malaria was transmitted in winter because the vector-mosquito did not hibernate, fed both on cattle and on people, and overwintered in houses and barns, taking an occasional blood meal without laying any eggs (most female mosquitoes bite in order to obtain nutrition to develop an egg batch). In the Sudan, low-level transmission occurs during the 10-11 month dry season, when day-temperatures are in the mid-40s. The vector-mosquito also shelters in houses, feeding occasionally on people and waiting for the brief rains in order to lay her eggs. Peak transmission occurs in the cooler rainy season.


  11.  This chapter appeared at a critical period of the climate change debate. Fully one third was devoted to mosquito-borne disease, principally malaria. The chapter had a major impact on public debate, and is quoted even today, despite the more informed chapter of the Third Assessment Report (see below).

  12.  The scientific literature on mosquito-borne diseases is voluminous, yet the text references in the chapter were restricted to a handful of articles, many of them relatively obscure, and nearly all suggesting an increase in prevalence of disease in a warmer climate. The paucity of information was hardly surprising: not one of the lead authors had ever written a research paper on the subject! Moreover, two of the authors, both physicians, had spent their entire career as environmental activists. One of these activists has published "professional" articles as an "expert" on 32 different subjects, ranging from mercury poisoning to land mines, globalization to allergies and West Nile virus to AIDS.

  13.  Among the contributing authors there was one professional entomologist, and a person who had written an obscure article on dengue and El Niño, but whose principal interest was the effectiveness of motor cycle crash helmets (plus one paper on the health effects of cell phones).

  14.  The amateurish text of the chapter reflected the limited knowledge of the 22 authors. Much of the emphasis was on "changes in geographic range (latitude and altitude) and incidence (intensity and seasonality) of many vector-borne diseases" as "predicted" by computer models. Extensive coverage was given to these models, although they were all based on a highly simplistic model originally developed as an aid to malaria control campaigns. The authors acknowledged that the models did not take into account "the influence of local demographic, socioeconomic, and technical circumstances".

  15.  Glaring indicators of the ignorance of the authors included the statement that "although anopheline mosquito species that transmit malaria do not usually survive where the mean winter temperature drops below 16-18ºC, some higher latitude species are able to hibernate in sheltered sites". In truth, many tropical species must survive in temperature below this limit, and many temperate species can survive temperatures of -25ºC, even in "relatively exposed" places.

  16.  The authors also claimed that climate change was already causing malaria to move to higher altitudes (eg in Rwanda). They quoted information published by non-specialists that had been roundly denounced in the scientific literature. In the years that followed, these claims have repeatedly been made by environmental activists, despite rigorous investigation and overwhelming counter-evidence by some of the world's top malaria specialists. [85]Moreover, climate models suggest that temperature changes will be relatively small in the tropics, and carefully recorded meteorological data—eg in the Brook-Bond tea estates in Kenya—shows no demonstrable warming since the 1920s. The IPCC authors even claimed that "a relatively small increase in winter temperature" in Kenya (!) "could extend mosquito habitat and enable .  .  . malaria to reach beyond the usual altitude limit of around 2,500m to the large malaria free urban highland populations, eg Nairobi. This despite the fact that in the 1960s the mosquitoes were present above 3,000m and Nairobi is at only 1,600m!

  17.  A similar claim was made that the dengue vector, Stegomyia aegypti was once limited to 1,000m in Colombia but had "recently been reported above 2,200m" One of the authors (the activist with the 32 different specialities) had recently published a claim (in The Lancet) that dengue had reached 2,200m "in the past 15 years". I had pointed out (again in The Lancet) that the publication he was quoting had categorically stated that dengue was not found above 1,750m. Moreover, although the maximum altitude of 2,200 m for the mosquito had been established (by two colleagues of mine) in 1979, this was the first ever investigation of the issue, so there was no evidence of an increase in altitude! Since that time, he has abandoned the claim that dengue has moved to higher altitudes, but still claims (eg in Janurary 2005 at a UNESCO conference in Paris) that the mosquito has leapt from 1,000 to 2,200m in a matter of 15 years.

  18.  In summary, the treatment of this issue by the IPCC was ill-informed, biased, and scientifically unacceptable. The final "Summary for Policymakers stated: "Climate change is likely to have wide-ranging and mostly adverse impacts on human health, with significant loss of life .  .  . Indirect effects of climate change include increases in the potential transmission of vector-borne infectious diseases (eg malaria, dengue, yellow fever, and some viral encephalitis) resulting from extensions of the geographical range and season for vector organisms. Projections by models .  .  . indicate that the geographical zone of potential malaria transmission in response to world temperature increases at the upper part of the IPCC-projected range (3-5ºC by 2100) would increase from approximately 45 per cent of the world population to approximately 60% by the latter half of the next century. This could lead to potential increases in malaria incidence (on the order of 50-80 million additional annual cases, relative to an assumed global background total of 500 million cases), primarily in tropical, subtropical, and less well-protected temperate-zone populations".

  19.  These confident pronouncements, untrammelled by details of the complexity of the subject and the limitations of these models, were widely quoted as "the consensus of 1,500 of the world's top scientists" (occasionally the number quoted was 2,500). This clearly did not apply to the chapter on human health, yet at the time, eight out of nine major web sites that I checked placed these diseases at the top of the list of adverse impacts of climate change, quoting the IPCC.

  20.  The issue of consensus is key to understanding the limitations of IPCC pronouncements. Consensus is the stuff of politics, not of science. Science proceeds by observation, hypothesis and experiment. Professional scientists rarely draw firm conclusions from a single article, but consider its contribution in the context of other publications and their own experience, knowledge, and speculations. The complexity of this process, and the uncertainties involved, are a major obstacle to meaningful understanding of scientific issues by non-scientists.

  21.  In the age of information, popular knowledge of scientific issues—particularly issues of health and the environment—is awash in a tide of misinformation, much of it presented in the "big talk" of professional scientists. Alarmist activists operating in well-funded advocacy groups have a lead role in creating this misinformation. In many cases, they manipulate public perceptions with emotive and fiercely judgmental "scientific" pronouncements, adding a tone of danger and urgency to attract media coverage. Their skill in promoting notions of scientific "fact" sidesteps the complexities of the issues involved, and is a potent influence in education, public opinion and the political process. These notions are often re-enforced by attention to peer-reviewed scientific articles that appear to support their pronouncements, regardless of whether these articles are widely endorsed by the relevant scientific community. Scientists who challenge these alarmists are rarely given priority by the media, and are often presented as "skeptics".

  22.  The democratic process requires elected representatives to respond to the concerns and fears generated in this process. Denial is rarely an effective strategy, even in the face of preposterous claims. The pragmatic option is to express concern, create new regulations, and increase funding for research. Lawmakers may also endorse the advocacy groups, giving positive feedback to their cause. Whatever the response, political activists—not scientists—are often the most persuasive cohort in science-based political issues, including the public funding of scientific research.

  23.  In reality, a genuine concern for mankind and the environment demands the inquiry, accuracy and skepticism that are intrinsic to authentic science. A public that is unaware of this is vulnerable to abuse. After careful review of the pronouncements the Health chapter in Working Group II the IPCC Second Assessment, it is my opinion that that they were not based on authentic science.


  24.  The third assessment report listed more than 65 lead authors, only one of which—a colleague of mine—was an established authority on vector-borne disease. I was invited to serve a contributory author on the health chapter

  25.  My colleague and I repeatedly found ourselves at loggerheads with persons who insisted on making authoritative pronouncements, although they had little or no knowledge of our speciality. At the time, we were experiencing similar frustration as Lead Authors of Health Section of the US National Assessment of the Potential Consequences of Climate Variability and Change (US Global Change Research Program). After much effort and many fruitless discussions, I decided to concentrate on the USGCCRP and resigned from the IPCC project. My resignation was accepted, but in a first draft I found that my name was still listed. I requested its removal, but was told it would remain because "I had contributed". It was only after strong insistence that I succeeded in having it removed.

  26.  Our deliberations in the USGCCRP are "public domain", ie they can be accessed by any member of the public. This is not the case for the IPCC. The final documents of the USGCCRP included clear statements of the complexity of the subject, and the limitations of models as predictors. We fought hard for the language of the document, and prevailed against fierce opposition, even to the point of insisting on the inclusion of a large map that clearly showed how dengue in Texas was limited by lifestyle, not climate.

  27.  My colleague was a top civil servant. He felt obliged to sit the IPCC project out, and to attempting to force a compromise. In a sense I believe he (we) succeeded. The 2001 report is much more comprehensive, more accurate, and gives a much better perspective of the diseases and their dynamics. The selection of references was biased towards models that predict an increase in range and prevalence of mosquito-borne disease, but there were refreshingly frank statements on the fundamental limitations of such models. Thus, the summary for policymakers made the following statement: "Many vector-, food-, and water-borne infectious diseases are known to be sensitive to changes in climatic conditions. From results of most predictive model studies, there is medium to high confidence that, under climate change scenarios, there would be a net increase in the geographic range of potential transmission of malaria and dengue—two vector-borne infections each of which currently impinge on 40-50 per cent of the world population. Within their present ranges, these and many other infectious diseases would tend to increase in incidence and seasonality—although regional decreases would occur in some infectious diseases. In all cases, however, actual disease occurrence is strongly influenced by local environmental conditions, socioeconomic circumstances, and public health infrastructure".

  28.  Transmission models are not a forecasting device. They are merely a means for exploring the interaction of a selection of relevant parameters. Moreover, there is no realistic way to test them in nature, nor any means to determine the "confidence limits" of their "predictions". No statistical evidence was given of the basis for these confidence limits; they appear to have been a purely subjective judgement, with no clear evidence as to why we should expect an "increase in incidence and seasonality" in the "present ranges" of malaria and dengue with "medium to high confidence". In my opinion, therefore, the sentence beginning: In all cases .  .  . should have come before any mention of the models, together with a clear statement that the models were purely speculative in nature.

  29.  Thus, despite the improved quality of the Third Assessment Report, the dominant message was that climate change will result in a marked increase in vector-borne disease, and that this may already be happening. The IPCC message has been repeated in the publications of other Agencies, often with inaccuracies that appear to have their origin in the Second Assessment Report. Thus the US Environmental Protection Agency persists in making the statement: `Global warming may also increase the risk of some infectious diseases, particularly those diseases that only appear in warm areas. Diseases that are spread by mosquitoes and other insects could become more prevalent if warmer temperatures enabled those insects to become established farther north; such "vector-borne" diseases include malaria, dengue fever, yellow fever, and encephalitis'.

  30.  Activist organizations, such as the World Wildlife Fund, continue to quote the IPCC statement that malaria can only be transmitted in regions where winter temperatures are above 16ºC. Several such organizations even claim that isolated cases of malaria in the USA and Canada during "particularly warm and humid periods" are compatible with the IPCC projections.


  31.  It will be interesting to see how the health chapter of the fourth report is written. Only one of the lead authors has ever been a lead author, and neither has ever published on mosquito-borne disease. Only one of the contributing authors has an extensive bibliography in the field of human health. He is a specialist in industrial health, and all his publications are in Russian. Several of the others have never published any articles at all.

  32.  The list of authors is of personal interest: I was nominated by the US Government to serve as a Lead Author. Nomination is a formal process, involving government officers at the highest level.

  33.   When I contacted IPCC personnel (at the Meteorological Office in Exeter) to see whether my nomination had been accepted, I initially received the message: "The IPCC received over 2000 government nominations during this process and most, such as yours, were of a very high standard. Unfortunately the IPCC Working Group Two Bureau did not pick you to be an author, although all nominations were scrutinised and assessed".

  34.   I replied with a question about the two Lead Authors that had been selected: "It is often stated that the IPCC represents the worlds top scientists. I copy to you the bibliographies of (the two lead authors), as downloaded from MEDLINE. You will observe that (the first) has never written a single article, and (the second) has only authored five articles. Can these two really be considered "Lead authors" with experience, representative of the world's top scientists and specialists in human health?"

  35.   I also pointed out that one Lead Author is a "hygienist", the other is a specialist in fossil faeces, and both have been co-authors on publications by environmental activists. I received the reply: "The selection criteria for IPCC Authors are defined in the "Principles and Procedures Governing IPCC Work" available on the IPCC website at: (These `Principles and Procedures' have been discussed, amended and agreed by Governments at several IPCC Plenaries)".

  36.  I pursued the question further, asking: (1) Who selects the Working Group/Task Force Bureau Co-Chairs? (2) Who are the Working Group/Task Force Bureau Co-Chairs for Group II, Health Impacts? Where is the Working Group/Task Force Bureau? (3) What are the criteria they use for identifying appropriate experts?

  37.   I received two replies, the simplest of which read: "Thank you for your continued interest in the IPCC. The brief answer to your question below is `governments'. It is the governments of the world who make up the IPCC, define its remit, and direction. The way in which this is done is defined in the IPCC Principles and Procedures, which have been agreed by governments. Please refer to my emails of 2 and 3 September for details on how to access that information".

  38.  In all the rules that were quoted, there was no mention of research experience, bibliography, citation statistics or any other criteria that would define the quality of "the worlds top scientists".

  39.   After all this correspondence, quite unexpectedly, I receive another message an IPCC person in Exeter: "I was looking today at the Access database which we use to manage the government nominations for the Fourth Assessment. I thought I would take the chance to check on your name. It turns out that you were not nominated for the Health chapter. You were nominated for the regional chapters, the four synthesizing chapters (17-20), and chapters 1 and 2".

  40.  I contacted Washington. They sent me the full set of official documents sent by executives of the Federal Government. There was absolutely no doubt: I had been nominated as a Lead Author for the Health chapter, and for several other issues that involved human health.


  41.  The natural history of mosquito-borne diseases is complex, and the interplay of climate, ecology, mosquito biology, and many other factors defies simplistic analysis. The recent resurgence of many of these diseases is a major cause for concern, but it is facile to attribute this resurgence to climate change, or to use models based on temperature to "predict" future prevalence. In my opinion, the IPCC has done a disservice to society by relying on "experts" who have little or no knowledge of the subject, and allowing them to make authoritative pronouncements that are not based on sound science. In truth, the principal determinants of transmission of malaria and many other mosquito-borne diseases are politics, economics and human activities. A creative and organized application of resources is urgently required to control these diseases, regardless of future climate change.

31 March 2005

85   In 2004, 10 of these specialists published a plea entitled "A call for accuracy" in The Lancet. Neverthess, environmental activists continue to make this claim, undeterred by the evidence. Back

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