The spots are timed to precede next week's theatrical release of "An Inconvenient Truth," a documentary film on global warming that features Gore, the former vice president and Democratic presidential candidate.

Against backdrops of a park, a beach and a forest, one celebrates the benefits of greenhouse gas-producing fuels.

"The fuels that produce CO2 (carbon dioxide) have freed us from a world of back-breaking labor, lighting up our lives, allowing us to create and move the things we need, the people we love," the ad runs. "Now some politicians want to label carbon dioxide a pollutant. Imagine if they succeed -- what would our lives be like then?"

The other ad questions media reports of the threat of climate change, especially a Time magazine issue devoted to the topic, and shows film of a glacier melting and then runs in reverse to show the glacier reconstituting itself.

"We had started work on this several months back, but we sort of changed course once the flood of glacier-melting stories began," said Sam Kazman, an institute lawyer who worked on the ads. "So we did want to get out there before the Al Gore film got into national opening."

'RUNNING FOR ARCH-DRUID'

Fred Smith, president of the institute, a nonprofit that advocates free enterprise and limited government regulation, said he had seen the film and found it "very alarmist," although well-produced.

"There's a lot of pictures of Al Gore pensively looking into the sunset," Smith said. "I don't think he's running for president, but he might be running for arch-druid."

The institute and environmental groups such as Washington-based Environmental Defense agree that average global temperatures have risen about 1 degree Fahrenheit (0.6 degrees Celsius) in the last century.

But the institute questions the impact of global warming while a broad range of scientists and environmentalists, including Gore, have linked it to more severe storms, melting ice caps and rising sea levels.

"They fly in the face of most of the science," Charlie Miller of Environmental Defense said of the institute ads. "The good news is that there's not a trade-off here between prosperity, jobs, growth and protecting the Earth. We can do both."

Environmental Defense and the Ad Council released public service announcements in March featuring children as future victims of global warming, and these were mentioned critically at the briefing where the new ads were released.