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."