The Democratic presidential contender, Sen. Barack Obama (Ill.), acknowledges that climate change is real, man-made and an "immediate threat."

From a July 2007 speech on the floor of the Senate: "I know that when it comes to the word 'carbon,' the range of views among my colleagues is varied and complex. I am among those senators who believe that carbon from human activities contributes to climate change, that it is an immediate threat, and that we must immediately require emission reductions through a strong cap-and-trade system."

Arizona Sen. John McCain, the Republican candidate, along with Sen. Joe Lieberman (I–Conn.), introduced the Climate Stewardship Act in the Senate in 2003—which was seen as a break with hard-line Republicans. He acknowledges that human activity accelerated global warming and proposes an "all of the above energy solution" called The Lexington Project to stem it.

From remarks made at a wind turbine-manufacturer in Portland, Ore., in May: "For all of the last century, the profit motive basically led in one direction—toward machines, methods and industries that used oil and gas. Enormous good came from that industrial growth, and we are all the beneficiaries of the national prosperity it built. But there were costs we weren't counting, and often hardly noticed. And these terrible costs have added up now—in the atmosphere, in the oceans, and all across the natural world."

Wild card:
Although McCain has a strong record with regard to global warming, his running mate, Alaska Gov. Sarah Palin, said in a recent interview: "A changing environment will affect Alaska more than any other state, because of our location. I'm not one though who would attribute it to being man-made." She softened her stance during a September 11 interview with ABC News's Charlie Gibson, saying "man's activities certainly can be contributing to the issue of global warming."

Obama plans to invest $150 billion dollars over the next decade to fund private efforts to develop alternative energies. He also wants to put a million 150-mile- (240-kilometer-) per-gallon plug-in hybrids on the road by 2015 and plans to raise fuel economy standards by 4 percent each year. He will also institute a cap-and-trade system to limit industrial carbon emissions. Carbon credits, which companies can buy if they pollute more than they are allowed, will be auctioned in a market set up by the government. The ultimate goal is to reduce carbon emissions to 80 percent below 1990 levels by 2050.

From a speech in Portsmouth, N.H., in October 2007: "No business will be allowed to emit any greenhouse gases for free. Businesses don't own the sky, the public does, and if we want them to stop polluting it, we have to put a price on all pollution."

McCain's platform revolves chiefly around monetary challenges for companies and consumers—including a $5,000 tax credit for consumers who buy zero-emission cars (encouraging automakers to create such vehicles) and a $300-million X PRIZE–like competition to develop a battery for plug-in hybrids and fully electric cars. Like Obama, he supports a cap-and-trade system—but in his version, the government gives carbon credits free of charge to companies who continue to pollute. His ultimate goal: bring carbon emission down to 60 percent below 1990 levels.

From an op-ed McCain wrote for The Financial Times March 19, 2008: "Americans and Europeans need to get serious about substantially reducing greenhouse gas emissions in the coming years or we will hand over a much-diminished world to our grandchildren. … We need a successor to Kyoto, a cap-and-trade system that delivers the necessary environmental impact in an economically responsible manner."