When Timberland, the outdoor clothing company based in New Hampshire, studied ways to reduce its carbon emissions four years ago, it weighed several options: building a wind farm in the Dominican Republic, buying power generated by renewable resources or setting up a vast bank of solar panels at one of its distribution centers in Ontario, California. It chose to do all those things, but that was the easy part. When Jeffrey Swartz, Timberland's chief executive, considered how much carbon dioxide was produced in making leather for the company's famous boots, the answer came as a surprise.

"As it turns out, the vast majority of the greenhouse gases associated with manufacturing leather comes from cows in the field," Swartz said. "Yes, methane."

While Timberland figures out how to cut these emissions it is examining ways to change the feed for cows the company has already cut its greenhouse gases by 17 percent from their 2002 level and aims to become carbon-neutral by 2010 by offsetting its emissions through renewable or alternative energy sources. Americans are increasingly recognizing that the effects of carbon emissions on global warming are a serious problem, but there are no rules in the United States regulating heat-trapping gases comparable to those that most other developed countries have adopted under the Kyoto Protocol. Some U.S.

businesses, though, are responding for a variety of reasons anyway: to satisfy customers or shareholders who worry about the environment, to improve their public image or to drive down their energy costs. For Timberland, while it shares the concerns over global warming, it is mostly a matter of dollars and cents. As Swartz put it: "What idiot will leave costs on the table? I hope it's our competitors. I get paid to create value."

Reducing carbon emissions is no easy task, but scientists, economists, environmentalists and a growing rank of business leaders warn that corporate America needs to move more quickly or it will face the consequences: higher energy prices, a potential cost for carbon pollution and, eventually, products that will have trouble competing globally because other countries are reducing emissions.

The United States is responsible for a quarter of all the carbon dioxide sent into the atmosphere each year. It has not ratified the Kyoto Protocol, the treaty on climate change that went into effect last year for more than three dozen countries, setting targets and timetables for cutting emissions. If consumption of fossil fuels continues at today's pace, the U.S. Energy Department has said, carbon emissions in the United States could rise to more than eight billion tons by 2030 38 percent above current levels. Many analysts predict that the United States will eventually set rules limiting greenhouse emissions.

Then, carbon pollution will turn into a cost of doing business.

In Europe, for example, companies that go over their emission limits must buy carbon credits to comply. Under the Continentwide trading system, the cost of a carbon credit last month reached a high of 30.50 a metric ton, or about $39.

But only 86 companies in the United States, accounting for 8 percent of U.S. carbon emissions, have enrolled in Climate Leaders, the U.S. Environmental Protection Agency's voluntary program to cut emissions. Meanwhile, emissions in the United States have risen 16 percent since 1990, the agency said. "There is certainly a lot of inertia in the economy, and many companies have their heads in the sand, wishing and hoping that somehow the overwhelming consensus among scientists is going to go away," said Alan Nogee, director of the clean energy program at the Union of Concerned Scientists, based in Cambridge, Massachusetts.

"But it's not," he said. "And ultimately their shareholders and customers are likely to pay a price. The reality is that carbon regulation is coming inevitably to the United States, as it has to the rest of the world."

Experts say large reductions in global emissions 50 percent or more by 2050 are needed to stop carbon concentrations from rising. "There is a lot that companies can do, especially in the area of energy efficiency," said Ashok Gupta, an economist at the Natural Resources Defense Council, an environmental group in New York. Not surprisingly, the biggest strides have been achieved by corporations with operations outside the United States. International Business Machines and DuPont, for example, have long had programs to curb their energy use. In doing so, they have managed to cut manufacturing costs while decreasing their emissions.

At DuPont, the savings from energy projects have totaled $2 billion over the past decade and a half. IBM has saved $115 million since 1998 by avoiding 1.28 million tons of carbon emissions, or the equivalent of taking 51,600 cars off the road, according to the climate change program at the World Wildlife Fund. Other companies, like 3M, Advanced Micro Devices and Gap, have pledged voluntary reductions in their emissions. Wal-Mart Stores, the world's biggest retailer, announced a sweeping set of environmental goals last October, including doubling its truck fleet's efficiency and improving energy efficiency at its stores.

Johnson & Johnson decided in the late 1990s to meet the Kyoto requirements. From 1990 to 2005, the company reduced carbon emissions by 11.5 percent. Meanwhile, sales grew 350 percent.

But some business areas remain averse to change. The transportation sector and utilities account for more than 55 percent of all emissions. Yet, for the most part, they are reluctant to commit to reductions without a government mandate. Bill McKibben, a resident scholar at Middlebury College in Vermont and the author of "The End of Nature," a book about global warming, said there was no single answer. "What people don't get is the scale of what needs to be done," he said. "Anybody whose solution includes the phrase 'in 20 years' hasn't quite caught on to where we are."