He also pushed for decisive action on a bill this year to limit emissions of heat-trapping gases, saying the legislation is needed for the U.S. to take a leading role in negotiations on a new international climate treaty later this year.
To underscore his point, Gore flipped through more than four dozen new slides showing melting ice caps, western wildfires, deforestation and oxygen-depleted seas in a hearing room where the lights were dimmed.
"We must face up to this urgent and unprecedented threat to the existence of our civilization at a time when our country must simultaneously solve two other worsening crises," Gore told the panel.
It was Gore's first appearance before Congress since March 2007. Six months ago, he called for the U.S. to produce all of its electricity from carbon-free sources within the next 10 years.
Since then, the recession has deepened and the government -- which is fighting wars in Iraq and Afghanistan -- has spent hundreds of billions to save financial institutions and keep automakers from bankruptcy.
Gore, who won a Nobel Peace Prize for his efforts to combat global warming, said the recession and wars should not delay passage of climate change legislation or U.S. participation in a new climate treaty.
The Bush administration pulled out of the last treaty, the 1997 Kyoto Protocol, citing a lack of participation by developing countries and harm to the economy. In the late 1990s, during the Clinton administration, the U.S. Senate balked at ratifying the agreement. Negotiations on a new pact are scheduled for December in Copenhagen, Denmark.
Senators in both parties express optimism that a bill requiring mandatory reductions in greenhouse gases could pass before the Copenhagen meeting.
But Republicans, particularly Sen. Johnny Isakson of Georgia and Sen. Bob Corker of Tennessee, pressed Gore on the role of nuclear power.
"If you accept every dire circumstance of climate change and you take a clean, reliable source of energy off the table. ... I don't think you can ever get to the solution you are seeking," Isakson said.
Gore said that he thought nuclear could play a small role, but would not be a "silver bullet." As for coal, he reiterated his position that no new coal-fired power plants should be built without the ability to capture and store carbon dioxide, the primary gas responsible for a warming climate.
Earlier this week, Obama signed orders that will boost the fuel efficiency of the nation's cars and trucks and could allow states to limit emissions of greenhouse gases from exhaust pipes.