Some Climate Research Not So Hot

by Howard Fienberg
April 27, 2001

The Intergovernmental Panel on Climate Change recently reported that a rising "risk of infectious disease epidemics" is "likely" to result from global warming. As the U.S. takes heat for rejecting the Kyoto Protocols, global warming has become more than an abstract specter; it is considered a tangible threat to public health through a coming plague of infectious diseases like malaria and West Nile virus. However, a new report from the National Research Council (NRC) found little evidence to justify such fears.

Questioning the validity of most climate models, the NRC recommended further research. In effect, the NRC report demonstrates that infectious diseases spread for many reasons. Global climate change is not obviously one of them.

Changes in the weather can have dramatic impacts on diseases and the pests that spread them. However, the NRC report, "Under the Weather," points out that the relationship traditionally drawn between climate and disease can be very misleading. Other influences, such as ecological, biological and societal changes, can have an even greater impact. For example, malaria and dengue outbreaks can be caused by anything from deforestation to population increases. Thanks to increased globalization, diseases can be transported worldwide in a matter of hours.

This does not mean that the climate has no impact. The life cycles of many disease pathogens and vectors are directly or indirectly influenced by changes in temperature, precipitation and humidity, affecting "the timing and intensity" of outbreaks. Trouble is that most of the links made between climate and disease result from imperfect computer models. Modern supercomputers can do amazing things, but effectively including all relevant factors in a climate model can prove a daunting task. Just as firing off a toy rocket in your back yard gives only an inkling of what the launching of the real space shuttle is like, so too do computer climate models only capture part of the story of infectious diseases. The NRC cautions that such models are good for some kinds of analyses, but "are not necessarily intended to serve as predictive tools," since they cannot "fully account for the complex web of causation that underlies disease dynamics."

The NRC report stresses that there are many more influences than climate, including "sanitation and public health services, population density and demographics, land use changes, and travel patterns." At essence, it concludes that, even assuming the prevention of global warming were a reachable goal, fighting global warming is an ineffective method of tackling infectious disease. Strong public health measures "such as vector control efforts, water treatment systems, and vaccination programs" are still the most effective tools.

So why do so many people still insist that climate change is the over-riding threat to public health? Many may simply fear admitting otherwise. Donald Burke, chair of the NRC panel which released the report, told National Public Radio that he felt "awkward" that the report was "not a strong endorsement that global climate change will lead to an inevitable holocaust of infectious diseases."

Last September, the magazine New Scientist interviewed Paul Reiter, chief entomologist at the U.S. dengue research lab in Puerto Rico. Interviewer Ehsan Masood, after noting that "even the slightest contrarian messages can be used by the oil and auto lobby to obstruct efforts to address global warming," asked, "whatıs wrong with emphasizing the risks of global warming if itıll lead to greater public awareness and investment in things like climate change research?" Reiter replied that the ends do not justify the means; the funding and commitment of honest science is required to handle infectious diseases. He concluded that it was "the advancement brought about by our modern economies that put these diseases at bay" in the developed world. By denying others the opportunity for that advancement "on the mere basis of emotive arguments founded on uncertain climate science... we will be committing a serious mistake."

Many believe that global warming is a looming global catastrophe. They may be right. But does this belief justify targeting global warming as the bogey for every scientific problem we face? Infectious diseases are a public health issue, first and foremost. Derailing public health solutions may suit the broader cause of environmental alarm, but it does not help victims of these diseases, either here or in the developing world.

HOWARD FIENBERG is research analyst with the Statistical Assessment Service (STATS), a nonprofit nonpartisan organization researching science and public policy.

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