House Republicans made it clear Wednesday they won't make things easy for Democrats trying to lay the groundwork for legislation on greenhouse gases and climate change.

At the first hearing of a special committee established by Speaker Nancy Pelosi to make the case for a bill, Republicans questioned efforts to paint global warming as a national security threat.

"Unfortunately, this debate hasn't been characterized by common sense. It's been characterized by extremism," said Wisconsin Rep. James Sensenbrenner, the senior Republican on the panel. "While this extremism hasn't done anything to produce effective solutions, it has created a lot of hot air, which hasn't been good for Congress' carbon footprint."

Sensenbrenner questioned "why global warming has suddenly become an issue of national defense" and afterward accused politicians and pundits of stoking children's fears.

Rep. Jay Inslee, D-Wash., said Sensebrenner's remarks reveal also that "there's a lot of fear in Congress."

Democrats who favor mandatory limits on "greenhouse" gases hope to send a bill to President Bush before the 2008 election. Bush favors more research and voluntary measures to slow the gases' growth.

The hearing was dominated by worries about global security and U.S. dependence on other countries for oil, rather than the usually cited climate change concerns: melting glaciers, rising sea levels and other threats from carbon dioxide and other warming gases that trap heat in the atmosphere like a greenhouse.

"It is a double threat, like Orthus, the monstrous two-headed hound of Greek mythology, with one head facing backwards and the other forwards," said Rep. Edward Markey, D-Mass., who chairs the new House Select Committee on Energy Independence and Global Warming.

"Our ever-rising oil dependence is directly attributable to a backwards-facing energy policy, while looking forward we can see the threat of rising temperatures and the subsequent increasing risk of natural and humanitarian disasters," he said.

The hearing coincided this week with first United Nations Security Council debate on climate change, where Britain argued that rising temperatures will spark global conflicts and developing nations countered that the issue wasn't worth the council's time debating.

A Virginia-based national security think tank warned this week that global warning gases pose a "serious threat" to U.S. national security. The report by The CNA Corporation was written by six retired admirals and five retired generals. It predicted worsening terrorism and fights involving the United States over dwindling natural resources that will result from a warming of the earth.

At the hearing Wednesday, Gordon Sullivan, a retired general who was the Army's chief of staff from 1991 to 1995, said global climate change "will be a significant threat to our national security and in a larger sense to life on earth as we know it to be."