US companies, unlike their counterparts based in most other industrialized countries, are not required to cut emissions because President Bush backed out of the Kyoto Protocol early in his first term. The pact went into force this year.

Scientists believe gases such as carbon dioxide, released when petroleum, coal and natural gas are burned, warm the Earth by trapping solar heat in the atmosphere. Many believe global warming can raise seas by melting glaciers and strengthen weather events such as hurricanes.

Responses to CDP's questions have created the world's largest database of corporate greenhouse emissions.

This year 60 percent of more than 250 US companies responded to the CDP, up from 42 percent last year. The results were revealed in New York on Wednesday.

"It's almost the embarrassment factor that companies don't want to be seen as laggards," said Chris Davis, head of climate change at Boston law firm Goodwin Procter.

"When their competitors ... have a good story to tell about how they're managing greenhouse gas emissions, I think it creates pressure to ... have a good story themselves," said Davis, who is not part of CDP, but helps clients deal with greenhouse risks.

He said CDP's questionnaire process has helped make US companies take climate change and their emissions seriously.

Growing numbers of US companies are beginning to shape emissions plans for many reasons. Either they have operations in other developed nations subject to carbon regulations, they are preparing for possible future state or federal US regulations, or they are worried about 2012, when current Kyoto regulations could be expanded to developing countries.

Microsoft Corp. is an example of a company that has changed its answers to CDP.

Last year, Microsoft told CDP it did not then quantify its emissions because it did not operate facilities that directly contributed to greenhouse gases.

This year, Microsoft responded that it was developing a greenhouse gas emissions inventory.

"Great companies like Microsoft can change and they do change," said Paul Dickinson, executive director of the CDP.

GDP said General Electric Co., which is managing its emissions in part by increasing sales of environmentally friendly technologies, such as wind and solar power, and utilities Duke Energy Corp. and Exelon Corp. are some of the leaders in low-carbon technologies and solutions.

GIVING COMPANIES PAUSE

The institutional investors that have signed on to CDP, including the California Public Employees' Retirement System, known as CalPERS, represent $21 trillion in investment.

"I think that gives companies some pause -- that the folks that might purchase their shares think this is an important issue of corporate management and governance," said Davis.

In this year's CDP, companies said they emitted 2.9 billion tons of carbon dioxide equivalent, according to James Cameron, chair of the project. While no such quantity is likely to soon be traded in emerging carbon emissions markets, carbon dioxide in European markets is currently valued above 20 euros a ton.

"Clearly, greenhouse gases are going to become a financial issue of increasing significance," said Cameron. He said that in the future, greenhouse gas trade could cause some shifts of wealth in companies.

Although companies are revealing more emissions, there is more work to be done, CDP said. Only 13 percent of companies that reported this year and last to CDP had recorded a reduction in their greenhouse gas emissions since last year.

Still, Stuart Eizenstat, a partner at Covington and Burling, who was Bill Clinton's chief Kyoto negotiator, said CDP progress has been steady.

"This is a classic example of what happens when the federal government creates a vacuum," he said.