Former Bush administration Environmental Protection Agency Administrator Christine Todd Whitman predicts the United States will respond to global climate change by enacting mandatory limits on carbon dioxide emissions from power plants and industries but that no action will occur before the 2008 elections.

Ms. Whitman, who spoke yesterday at the Air & Waste Management Association's annual conference in Pittsburgh, said she favors a cap-and-trade program over an across-the-board policy limiting emissions to reign in the greenhouse gases that exacerbate climate change.

"A market-based cap-and-trade program can and will work," she said, "and the sooner we engage in that type of control, the better off we will be."

Such a program, she said, could be modeled after the successful acid rain control program. It could set a cap or limit on the total amount of carbon dioxide emitted and allow utility companies and industries to decide where to cut emissions by trading credits between those that make the reductions and those that don't.

Ms. Whitman said global warming is "not a partisan issue," and a federal response makes more sense than the "patchwork quilt" of state regulations and programs that have filled a vacuum created by the Bush administration's inaction.

"Most of the states would adopt federal greenhouse gas limits if Congress acts," she said, "but carbon regulation probably won't happen before 2008. We need to be ready to go once the election is over."

Ms. Whitman said the nation's greenhouse gas control policy should include a new emphasis on nuclear power and encourage people to buy hybrid vehicles to reduce mobile source pollution.

Government should also be encouraging development of renewable energy sources and use of alternative fuels, she said, but not corn-based ethanol production, which is inefficient to produce, transport and burn and is driving up food prices.

"It's a case of political science trumping actual science," she told an audience that was much friendlier than the one she had faced Monday in Washington, D.C., where her testimony to a congressional committee about air quality in New York City following the Sept. 11, 2001, terrorist attack was booed by rescue workers. She declined to discuss that topic yesterday.

Her speech was the third to address greenhouse gas issues at the four-day conference of the Pittsburgh-based, not-for-profit organization of environmental professionals, and reflects the gathering's focus on climate change.

At a panel discussion yesterday titled "Climate Change: Electric Power Industry Perspectives," there was consensus that such a change is occurring, and human-produced emissions are having a major impact. Discourse focused on how greenhouse gas emission controls should best be imposed.

Ray Butts, manager of environmental services for Florida Power and Light, said the 65 percent to 70 percent reductions in carbon dioxide emissions needed to stabilize atmospheric carbon can be achieved only by mandatory limits on all sources: utility companies, industries and vehicles.

He said his company and the Climate Action Partnership, a joint utility, business and environment advocacy group, favor enactment of a federal carbon fee that would "change the behavior" of polluters and provide money to support research and development on new technology to capture and sequester carbon emissions.

Martin Smith, manager of energy policy for Xcel Energy, which has 3.3 million customers in eight Western states and uses coal for almost half of its fuel, said a carbon tax penalizes companies that use a lot of coal. Instead, he proposed they meet clean energy portfolio standards that require they get a minimum of 20 percent to 25 percent of their fuel from clean and renewable sources.