President Bush's decision to withdraw from an international climate treaty last year will, in the long run, save billions of dollars and millions of jobs, his top environmental adviser told a Senate panel Thursday.

"The Kyoto Protocol would have cost our economy up to $400 billion and caused the loss of up to 4.9 million jobs, risking the welfare of the American people and American workers," said James L. Connaughton, chairman of the White House Council on Environmental Quality.

Connaughton and Bush's senior advisers for science and economic matters also presented White House views on climate change Thursday before Democratic senators in charge of the Senate Commerce, Science and Transportation Committee.

Sen. John Kerry, D-Mass., said the administration must move beyond mere "rhetoric" in setting goals for long-term cuts in emissions of heat-trapping greenhouse gases blamed by many scientists for global warming.

Bush's plan calls for voluntary action by industry contrary to the treaty negotiated in Kyoto, Japan, in 1997 that calls for mandatory reduction of those gases by industrial nations.

The Bush administration says it may need as long as five years to develop scientific forecasts before deciding how best to address global warming.

Assistant Commerce Secretary James R. Mahoney told senators Thursday, as he did a House committee Wednesday, that the administration is "now ready to move into a new time of differentiation and strategy evaluation" extending over the next two to five years -- depending on whether President Bush is re-elected in November 2004 -- that would help the nation develop strategies to minimize climate change risks.

Rep. Sherwood Boehlert, R-N.Y., chairman of the House Science Committee, praised the competence of administration officials but expressed dissatisfaction with what they described as limited information being provided about the White House's climate change policies.

"We really don't have a policy" on global warming, said Rep. Mark Udall, D-Colo.

John H. Marburger III, the White House science adviser, appeared before the Senate and House committees with Mahoney, saying humans have been a major producer of greenhouse gases, and that these gases -- often produced by the burning of oil and coal -- have contributed to climate warming.

Marburger's remark comes a month after Bush dismissed a report his administration submitted to the United Nations as having been "put out by the bureaucracy."

The report mostly blamed human activity for global warming but acknowledged some lingering scientific uncertainties.

The White House favors a response to global warming that relies on increased spending on science and technology and on voluntary, not mandatory, measures to slow the rate of growth in gas emissions.

"We know we have to make very large changes if this turns out to be a problem," Marburger told the panel Wednesday. "The consequences of human-induced global warming could be quite severe."

Mahoney seemed more convinced of the science behind global warming.

"The issue isn't, 'Is there a problem?"' Mahoney said. "The issue is, 'What specifically do we do about the problem?"'