Global Warming: Public Health and the Debate about Science and Policy

Article excerpt

Considerable attention continues to focus on the science and policy aspects of the global warming debate and the potential for negative health effects associated with the predicted changes in climate patterns. As with many public policy issues, the debate is shaped by two competing views. There are those who say it is all a hoax and compare global warming to alar in apples, Times Beach, and the cranberry scare of 1959. Others suggest that we are beginning to see the effects of global warming now and should take decisive action to slow the change that is taking place. Where on this continuum does the truth lie? That is the issue for science and policy.

As has been the case with other environmental issues, the science is not definitive. We must extrapolate from what is known to predict what will happen.

A fundamental point is being overlooked, however, while scientists debate and economists worry. That point is a message about prevention, protection of public health, and preservation of the environment, all of which should influence the interim policy decisions made while we wait for greater scientific certainty. There is sufficient science to support steps toward mitigation or prevention of adverse effects even in the absence of a complete explanation of global warming as a short-term anomaly or a prelude to irreversible change.

Paul Epstein, of the Harvard Medical School, has described a framework for assessing health, climate change, and ecosystem vulnerability. Using the analogy of the disease triangle (agent, host, and environment) Epstein's framework defines three spheres: climate system, ecosystems, and social systems. Each of those three spheres can influence the nature and rate of change in the others. The current dispute among scientists and policy makers concerns the specific influence of the climate system sphere, particularly the implications of the global warming phenomenon. There is less uncertainty, however, about the factors that influence change in the other spheres. For example, it is known that the consumption of fossil fuels is generating greenhouse gases and releasing them into the atmosphere at an unprecedented rate. Likewise, activities such as deforestation are changing and, in some cases, destroying ecosystems. It is also known that these changes entail a loss of diversity through the extinction of plant, insect, and animal species. Environmental factors include overharvesting, loss of habitat, and the emission of chemical pollutants. Each of those factors can be measured quantitatively.

While the meaning of the rise in global temperature and effects such as increasing ocean levels continue to be disputed, the spread of certain diseases has been clearly documented. Those diseases have been found at latitudes where they have not previously been identified. The increased incidence of hantavirus, malaria, cholera, and toxic algal blooms suggests a change in ecological balance and predator-prey relationships that can influence the risk of disease in humans. Regardless of whether there is a proven relationship between global warming, climate changes, and the emergence of new patterns of infectious disease, the public health community is obligated to investigate these new trends and determine what additional analysis and intervention are necessary. Public health practitioners frequently respond to disease incidence well before any cause-effect relationship has been established. The determination of causal factors will ultimately enhance the ability to intervene effectively, but the lack of such a determination does not have to be a barrier to response.

Scientists are facing the following questions: What is the capacity of the global environment to manage the assault by greenhouse gases, pollutants and human activity? …