From Christmas Day in 1991, when the white, blue and red Russian flag rose over the Kremlin, symbolizing the end of the Soviet Union, the U.S. assumed a dominant presence in world affairs the likes of which has not been witnessed since the Imperium Romanum. Yet the nation that endorsed the idea of preemptive military action has acted with remarkable passivity when it comes to an energy policy that deals with climate change.

In a recent scholarly article, economist Jeffrey D. Sachs and geophysicist Klaus S. Lackner of Columbia University noted that the Bush administration's impulse on global warming has been to wait for "something to turn up"--say, the discovery of a plentiful, noncarbon fuel or a technique to eliminate greenhouse emissions at low cost. Global warming has never been the priority it should be.

The reasons are not hard to fathom. People worry that the consumerist way of life that Americans have come to accept as a birthright will have to be scaled back. After all, on average, each U.S. citizen has more than twice the energy consumption of a western European, according to statistics for 2003, and almost 10 times that of a Chinese. To narrow this gap, the U.S. will have to alter its energy-intensive habits. But that doesn't mean we must all live in cardboard boxes. In every plan to tackle warming, Americans will still be better off in 2050 than they are today.

Both technical and policy farsightedness will be needed to achieve the concurrent objectives of growth and sustainability. Decades may pass before hydrogen-powered trucks and cars relegate gasoline- and diesel-fueled vehicles to antique auto shows. In the interim, conservation and better efficiencies in both transportation and electricity generation and usage will allow us to muddle through. Yet for even that to happen, the world's leading economy--and emitter of almost one quarter of human-generated carbon emissions--will have to assume the leadership role that it has so far largely shirked.

Regaining a modicum of credibility will itself prove an immense undertaking. Both the president and Congress need to endorse the ever expanding body of evidence that points to the reality of warming and listen to, rather than harass, scientists who arrive bearing bad news.

Funding for energy research must be accorded the privileged status usually reserved for health care and defense. Yet rhetoric needs to go beyond the mantra that before taking action, more research is needed to eliminate uncertainties surrounding climate science. A ceiling on greenhouse emissions should be set, and then the market should decide how to achieve that target through sales and purchases of emissions allowances. Other measures that must be adopted include stiffened fuel economy standards, carbon taxes and requirements that the largest producers of greenhouse gases report their emissions publicly.

The U.S. should lead by example. An aggressive domestic program would enable this country to influence China, India and other fast-growing developing nations to control emissions. Without the U.S. at the head of the table, the prospects for any meaningful action on a global scale will gradually recede along with the Arctic glaciers.