Scientists often must act on uncertainty

By Bernice Wuethrich

Today in Japan, 150 countries concerned about global warming will begin making decisions that could shape the world economy and environment well into the next century. And they'll do it on the best guesswork science can offer.

Neither those who fear global warming nor those who soft-pedal the threat can prove their claims. Uncertainty abounds. But worry not. Scientific uncertainty is a given, not an obstacle.

Take, for example, the medical community's approach to complicated health issues for which there is a significant body of information but no ready cure - breast cancer, prostate cancer and heart disease, to name a few. Leading organizations such as the National Institutes of Health and the American College of Cardiology routinely call "consensus conferences" to deal with such issues. They bring together leading experts in the field to review every relevant scientific paper and clinical study. They grapple with contradictory studies, new data and old data. Confronted with the need to treat a killer such as acute heart failure, there is an imperative to act.

Therefore, earlier this year, the American College of Cardiology and the American Heart Association published the results of a year-long consensus conference on acute heart attack. Its recommendations superseded those from 1990. No one is saying the authors of the 1990 study were incompetent or acted hastily. They acted on what was known at the time, and their guidelines, when implemented, helped to save lives.

That 1990 meeting is similar to this year's global warming convention. Will the answers be perfect? No. Will we have to change them sometime in the next decade? It's a sure bet. But like a heart attack, global warming cannot be left until later.

This year's report on acute heart failure includes guidelines for the use of clot-busting drugs, aspirin and drugs that curtail the enlargement of the heart. These recommendations are made despite the fact that the root cause of the hardening and plugging of arteries remains a mystery. Future discovery of the genetic and biochemical factors that explain why one person's arteries clog up while another's remain clear will undoubtedly lead to new treatments. In the meantime, it makes good sense to act upon what is known.

Scientists trying to understand the climate of the Earth are dealing with an entity no less complex and mysterious than the human body. Climatologists use the same principles of biology, chemistry and physics as do medical researchers.

Climate science has a great deal of uncertainty. Nonetheless, the representatives meeting in Japan must translate all that is known and unknown about climate change into policy. They will be acting upon the report of the United Nations' Intergovernmental Panel on Climate Change (IPCC). The report, compiled by 78 leading scientists and 2,000 contributors and reviewers, projects a global warming of 3.5 Fahrenheit degrees over the next 100 years if greenhouse gas emissions, caused by the burning of fossil fuels, are not reduced.

As the Kyoto conference opens, the media are inundated by reminders of all the unknowns. Computer climate models cannot completely replicate reality, the effects of climate feedback caused by clouds and dust are sketchily understood, and we have little understanding of the climate's natural variability. What if the IPCC's nine-year process, its players and scientific presumptions are no more substantial than thin air?

The fact is that in all areas of science, uncertainty is paramount. Almost every new insight about the universe starts as a tentative finding, open to wide debate. Scientific consensus is hard-won and often transitory, but it the best guide we have.

While it is easy to say "heart attacks are bad, and we should stop them," global warming may seem neither as immediate nor as personally threatening. And while the natural history of global warming may appear less obvious than that of the hardening of arteries, it is clear enough to 2,000 of the world's leading climatologists.

Kyoto is an opportunity to inaugurate a new era of international cooperation on a global problem. Enforceable guidelines that limit output of greenhouse gases may not be as easy as taking an aspirin when chest pains strike, but it's easier than resuscitating a heart that has stopped.

Bernice Wuethrich is a free-lance science writer and an exhibit writer for the Smithsonian Institution.

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