William H. Schlesinger Photo:Jon Gardiner

At any moment, science gives us its best explanation of reality. It proceeds by rigorous tests of hypotheses through observation and experimentation. For centuries, we thought the Earth was the center of the universe, until Galileo used the scientific method to prove otherwise. Universities are full of those who hope to disprove existing postulates; fame as a scientist among your peers comes from overturning dogma. In this way, the progressive refinement of science has brought us modern health care, abundant food, and many of the conveniences of daily life.

We all trust science when we read the daily weather forecast and decide what to wear to work. Later in the day, we may change our understanding of reality, but as we leave for work, we act with the best knowledge we have at the moment. That knowledge is informed by the science of meteorology and its models of how the weather system works. Like all science, meteorology undergoes constant scrutiny and refinement. Its predictions will improve with time, but for the moment, only a rain dance offers an alternative.

Charles Darwin proposed his theory of evolution more than 150 years ago and, to date, no better explanation for the history of life on Earth has appeared in the scientific literature. More than a century ago, the Swedish chemist Svante Arrhenius suggested that the radiative properties of carbon dioxide in the atmosphere would warm the Earth. We are now living in that reality, and the scientific community has achieved unprecedented consensus on the fate of a planet with rising CO2 in its atmosphere.

Certainly, if new science provided better explanations for the appearance and disappearance of the diverse forms of life during Earth's history or for the processes that control the temperature of our planet, the scientific world would embrace them. But countless scholars who have tried to leave their mark on the fields of evolution and atmospheric physics have failed to provide alternative explanations of substance.

I marvel, then, that those who simply wish the world worked otherwise can prevail in the public-policy world. The contrarians of evolution and global warming do not muster science to support their views; rather, they trust their beliefs to be true even in the face of science. Unfortunately, speaking against the uninformed faith of the contrarians has now reduced scientists to the status of a special-interest group in the halls of government.

Nowhere is this more apparent than in the current debate about climate change. A vast majority of the scientific community has achieved consensus about global warming, but a small ideological minority persists in disrupting the creation of effective policy--not basing their criticism on science but using an active program of empty rhetoric to confuse the issue. One well-known climate scientist has even been the subject of a congressional inquiry that is a thinly veiled vendetta against his peer-reviewed findings. Many of these ideologues have a deep stake in the status quo. Unfortunately, the longer we wait to limit the emissions of carbon dioxide into the atmosphere, the less likely it is that we will avoid the negative impacts of global warming. Management of a planet does not turn on a dime.

We all are vulnerable to global warming, whether from an increased exposure to tropical disease, rising sea levels that may flood a vacation home, or catastrophic crop failures in the Great Plains. Firm government action to prevent climate change is as crucial to our future as the prevention of terrorism and the suppression of nuclear weapons. Whatever policies we adopt to mitigate climate change must be simple, fair, and effective. Good science has much to offer to the policy-development process.

Certainly, some blame for the marginalization of science rests with scientists themselves, who too frequently have been reluctant to come outside the Ivory Tower to explain what they do and why it is important. During the past year, the Nicholas School published a series of "advertorials" on environmental issues in The New York Times, which produced an outcry of dissent from a small number of faculty members, who felt it was inappropriate for the school to take a stand on issues of climate change, mercury emissions, and beach erosion. Each ad, however, was informed by scientific research in the Nicholas School, often funded by public dollars granted to its faculty. I believe that for us to sit quietly while the uninformed determine government policy on major environmental issues is an unacceptable return on public investment.

Science must not be politicized, but scientists are not advocates when their expertise informs the political process. While genomics, nanotechnology, and computer science can often promise a better world, environmental science frequently warns us of the dangers that lie ahead. For environmental scientists, success is often manifest by the forest that wasn't cut. Healthy humans depend on a healthy planet. Environmental scientists must teach the importance of preserving natural, functional ecosystems, and we must be eager to articulate that message clearly to the general public.

We hope that clear, forceful statements of science from the Nicholas School and through the new Nicholas Institute--created this year to foster the translation of environmental science to policy--will make it easier for those we elect to be true leaders of government and will return us once again to a time when sound science informs policy.

Schlesinger, dean of the Nicholas School of the Environment and Earth Sciences, is James B. Duke Professor of biogeochemistry.