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© International Epidemiological Association 2001 International Journal of Epidemiology 2001;30:655–657 Printed in Great Britain Climate change and health: information to counter the White House Effect AJ McMichael Within two months of assuming office, George Bush openly reneged on his electoral commitments to reduce the nation’s industrial carbon dioxide emissions and withdrew the US from the international Kyoto Protocol, forged in 1997 and which seeks to slow global climate change. These things were done, he says, in the interests of protecting the nation’s economy and workers. They were also done, of course, to pay off several powerful private-sector interests—although few people expected the political debt-settling to be quite so blatant. There may well be, however, a silver lining to this cloud of continuing greenhouse gases from American cars, power-plants and factories. Bush claims that the science of climate change is flawed and unconvincing. He asserts that action taken now would be premature and prejudicial to the US national interest. These several ill-informed claims will have a cathartic effect on the public debate. They will force us all to reconsider the nature and limitations of scientific evidence, to understand more clearly the pervasive influence of uncertainty in the modelling and forecasting of complex biophysical and ecological systems, and to clarify the role of the Precautionary Principle as a necessary basis for prompt decision-making in situations where unavoidable scientific uncertainty is accompanied by potentially serious risks.1 That principle, formally endorsed by member states at the United Nations Conference on Environment and Development, in Rio de Janeiro, 1992, states: ‘Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing costeffective measures to prevent environmental degradation’. In the popular imagination, and in the minds of many policymakers, there persists a false view of ‘science’. Many people see ‘science’ as the source of new knowledge, precise estimation, and foolproof technologies. Many politicians want from scientists ‘a number’; they do not want uncertainty ranges, probabilities or alternative scenarios.2 But now more than ever, as we encounter the prospects of adverse consequences from global climate change, stratospheric ozone depletion, biodiversity losses, the spread of invasive species, disruption of the global elemental cycles of nitrogen and sulphur, declining supplies of freshwater worldwide and the global dissemination of persistent (often chlorinated) organic chemicals,3,4 we are going to have learn to deal in a more complex and less certain currency of scientific assessment.1 The Bush debacle also underscores the requisite international nature of Kyoto-like agreements. The world’s climate system is a global public good, a common-property asset. Given the now prodigious scale of human numbers and economic activity, Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK. E-mail: tony.mcmichael@ lshtm.ac.uk protection of the world’s climate will henceforth require agreed international stewardship. It is therefore nonsense for any country to talk of going it alone—particularly as profligate consumers—when what is at stake is global climatic stability. Tropical cyclones, intensified rain and flooding, more frequent heatwaves, and a generalized destabilization of ecosystems (including those that underpin agriculture) will all impinge on Americans as on everyone else. Bush and his scientific advisors may or may not actually believe that the science of climate change is flawed. After all, for decades we heard the tobacco industry claim that the evidence of cancer risk from smoking was flawed—even as that iniquitous industry secretly garnered its own clear-cut experimental evidence of the addictiveness and carcinogenicity of tobacco smoke. Meanwhile, the reality is that the science of climate change has evolved rapidly over the past decade. Climatologists now have sophisticated models that give a good representation of past observations of atmospheric change and climate variation—models that link up the interactive relations between ocean, atmosphere, cryosphere, terrestrial carbon fluxes and human-made industrial aerosols.5,6 Scientists in many other disciplines have credible ways of estimating how scenarios of future climate change will impinge upon agriculture, forests, fisheries, coastal zones, freshwater circulation, marine ecosystems and so on. More recently, epidemiologists and other health researchers have begun to clarify the actual and potential impacts of global climate change upon human population health. This emerging picture of climate change and its many impacts is now coalescing into a strong and coherent story. The scientific evidence has been authoritatively and painstakingly assessed by the International Panel on Climate Change. This panel, the IPCC, was established in the late 1980s by the UN system, to advise national governments on the processes, consequences and ways of lessening climate change. The IPCC’s Third Assessment Report, the result of five years of intense peer-reviewed work, was finalized in early 2001.6 Four conclusions stand out from that work:7 1 The great majority of the surface warming (around 0.4°C) that has occurred over the past quarter century has been due to greenhouse gas emissions by human populations. That is evident from the particular pattern of warming (e.g. night-time increases exceeding daytime increases), which distinguishes it from warming due to natural causes such as volcanic activity and increased solar activity. 2 The estimated range of global average temperature increase over the coming century is higher than previously estimated. Those estimates lie mainly within the range of 2–5°C. Rainfall will also increase (as evaporation, inevitably, increases). 655 656 INTERNATIONAL JOURNAL OF EPIDEMIOLOGY 3 Many simple physical and biological processes have already been affected by climate change. These include glacier retreat, permafrost thawing, sea-ice reduction, earlier bird-nesting, earlier insect hatching, polewards shifts in various animal and plant species, and earlier bud-burst. Taken in aggregate, these constitute a plausible and compelling pattern of climateinduced changes in relatively simple environmental systems. 4 There has been an increase in adverse impacts upon human wellbeing, physical infrastructure, physical safety and health caused by the increase in frequency and intensity of extreme weather events over the past several decades. This, at least in part, is attributable to climate change. For epidemiologists, an important new research task now looms. In a stable world, with unchanging climate, we may have taken little interest in how climatic conditions affect health outcomes. After all, we cannot (or could not!) intervene to change the climate—although we can intervene in ways that protect people against adverse climatic exposures. In today’s world, with human-induced climate change, that rationale is irrelevant. We epidemiologists must therefore improve our capacity to estimate future health impacts of climate change, using sophisticated model-based risk assessment procedures. Of rapidly growing importance—including as part of the antidote to political ignorance, cynicism and sheer folly—we must also develop improved research methods for the early detection of the health impacts of climate change. Indeed, it is already clear that the latter task has both scientific and political importance. Policymakers have become aware that the toll of climate change damage might include adverse health effects, particularly in developing countries. Nevertheless, the available evidence for that has been slim. If, as many scientists suspect, the risks to human health are wideranging and potentially severe, then the sooner we adduce evidence for that, the better informed will be the public discourse. Such research is likely to show that climate change represents, for humans (as for other species), the disturbance of a basic ‘life-support system’.8 Such evidence would count enormously in the future policy debate. There has been a recent surge of interest in this domain. For example, the World Health Organization (WHO) European Region has embarked on a co-ordinated plan of seeking evidence of early impacts of climate change.9 This includes studies of trends in heat-related deaths, the health impacts of weather disasters, summer food-poisoning, pollen-related allergies, and the seasonal and geographical modulation of vector-borne infectious diseases. Several US-based funding agencies are now supporting a new programme of international research into climate variability and human health, with particular interest in impacts on infectious diseases. This evolving research narrative now includes a project to assess the health impacts of biodiversity loss (including as a result of climate change), as a joint activity between Harvard University and the WHO. Various of the world’s universities, have recently established new centres of research focusing on the health consequences of environmental change, globalization, and other international processes. New textbooks are appearing on this topic.10 Understandably, we may wring our hands in despair at the appalling reasoning and selfish nationalism of the George Bushes of this world. Better, though, to ensure that policymakers and politicians hear clearly the considered assessments of the world’s scientific community. The role of the IPCC, whose Third Assessment Report is being published in mid-2001,6 has been and remains a crucial source of up-to-date information and well-documented assessments in this international policysetting arena. We epidemiologists must also get on, even more urgently, with the task of elucidating how climate change and other global environmental changes are affecting and will affect human population health. In light of the past decade’s increased research tempo, our understanding of the dependence of human societies on the continued functioning and productivity of this planet’s great biogeochemical systems has grown rapidly. This is imparting a new and precious ecological perspective to our thinking— a perspective that makes clear that, in the long run, it is the conditions of the social and natural environments that set the limits to human health and survival and that determine the patterns of disease.8 To date, regrettably, that perspective has lain beyond the more limited horizons of Modern Epidemiology. We must not underestimate either the potential magnitude of these global-scale issues as they evolve over the coming decades, or therefore the importance of our research efforts. The international challenge in relation to global climate change is not merely one of implementing the Kyoto agreement. That agreement is merely a start: a 5% cutback in greenhouse gas emissions over the preceding and current decades, limited to developed countries. From the now-maturing science of climate change and its impacts, scientists estimate that a worldwide reduction in greenhouse gas emissions of around 65% will be necessary over the next half-century if ecologically damaging climatic change is to be averted.11 That would require a reversion to globally-averaged levels of per-capita carbon dioxide emissions equivalent to those of around 1920; and that, in turn, would constrain the ongoing rise of atmospheric carbon dioxide levels to approximately twice the pre-industrial level. To achieve this will require some radical transformation of our social priorities and our energy-generating technologies. Even so, climate scientists tell us that the world’s seas would continue to rise for up to a thousand years, as the high-inertia processes of heat uptake and expansion by deep ocean waters continues.6 George Bush’s recent decisions may, on charitable interpretation, indicate that he and his advisors are uninformed and out of their depth on this complex topic. Unless the US, as premier emitter of greenhouse gases, plays an enlightened participatory role in the international effort to curb climate change, many future generations of coastal-dwellers may also be somewhat out of their depth. As global environmental change looms larger on the international agenda of science and policy, attempts at selfish opting-out by nations will become as intolerable as they are irrational. Research that elucidates the risks to human population health can help to make that case. References 1 Raffensperger C, Tickner J (eds). Protecting Public Health and the Environment: Implementing the Precautionary Principle. Washington, DC: Island Press, 1999. 2 Levins R. Preparing for uncertainty. Ecosystem Health 1995;1:47–57. INFORMATION TO COUNTER THE WHITE HOUSE EFFECT 3 McMichael AJ, Beaglehole R. The changing global context of public health. Lancet 2000;356:495–99. 4 Vitousek PM, Mooney HA, Lubchenco J, Melillo JM. Human domination of Earth’s ecosystems. Science 1997;277:494–99. 5 Hadley Centre. Climate Change: An Update of Recent Research from the Hadley Centre. London: DETR/UKMO, 2000. 6 Intergovernmental Panel on Climate Change. Climate Change 2001. Third Assessment Report. Vols I–III. Cambridge: Cambridge University Press, 2001. 7 Intergovernmental Panel on Climate Change. Summary for Policymakers—Climate Change 2001: The Scientific Basis. Cambridge: Cambridge University Press, 2001. 657 8 McMichael AJ. Human Frontiers, Environments and Disease: Past Patterns, Uncertain Futures. Cambridge: Cambridge University Press, 2001. 9 Kovats RS, Menne B, McMichael A, Bertollini R, Soskolne C (eds). Climate Change and Stratospheric Ozone Depletion. Early Effects on our Health in Europe. (WHO Regional Publications, European Series, No. 88) Copenhagen: WHO Regional Office for Europe, 2000. 10 Martens WJM, McMichael AJ (eds). Environmental Change, Climate and Health. Issues and Research Methods. Cambridge: Cambridge University Press, in press. 11 McMichael AJ, Powles JW. Human numbers, environment, sustain- ability and health. Br Med J. 1999;319:977–80.