The Republican presidential candidates shown leading the race in recent polls all believe global warming is a serious threat and caused by human activity.

Audience members listen to Republican presidential candidates at debate in Iowa (courtesy: Des Moines Register)

When asked at today's Des Moines Register debate in Iowa to raise their hands if they believed climate change were indeed a real problem caused by people, Sen. John McCain, former Mayor Rudy Giuliani, former Gov. Mike Huckabee and former Gov. Mitt Romney all responded in the positive.

"Climate change is real. It's happening. I believe human beings are contributing to it," Giuliani said, calling for a "Manhattan Project" to wean America off foreign energy sources.

McCain chimed in, saying, "More than contributing, my friend."

"But let me put it to you this way: Suppose that climate change is not real and all we do is adopt green technologies which our economy and our technology is perfectly cable of. Then all we've done is given our kids a cleaner world," McCain said. "But suppose they're wrong and climate change is real and we've done nothing. What kind of a planet are we going to pass on to the next generation of Americans?"

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Mitt Romney, who has fallen behind the surging Mike Huckabee in Iowa, said the United States could not act alone.

"We call it 'global warming,' not 'America warming,'" Romney said. "So let's not put a burden on us alone and have the rest of the world skate by without having to participate in this effort. It's a global effort."

Those not raising their hands on the original question of global climate change being a serious threat caused by human activity were former Sen. Fred Thompson, Reps. Ron Paul, Tom Tancredo and Duncan Hunter, and Ambassador Alan Keyes.

When Keyes was asked his thoughts, he gave a long answer condemning the betrayal of U.S. sovereignty, elite politicians and the destruction of the Constitution.

Thompson jumped in to say: "I agree with Alan Keyes' position on global warming."

As the audience laughed, Keyes said: "I think the most emission we need to control is the hot air emission of politicians who pretend one thing and don't deliver."

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