A look at the past positions on climate change of some of the GOP presidential contenders, and what they're saying now:
Then: "Now it's time for Congress to act by capping greenhouse gas pollution." _ Environmental Defense Action Fund ad, 2007.
Now on the science: "This is an issue that ought to be answered by the scientific community. I'm not a meteorologist. All I know is 90 percent of the scientists say climate change is occurring." _ Time magazine, May 23, 2011.
Now on the policy: "Cap-and-trade ideas aren't working; it hasn't worked, and our economy's in a different place than five years ago. Much of this discussion happened before the bottom fell out of the economy, and until it comes back, this isn't the moment." _ Time magazine, May 23, 2011.
Then: "If we act now, we can create thousands of new jobs in clean energy industries before our overseas competitors beat us to it. So come on, Congress, let's get moving. ... Cap greenhouse gases now." _ Environmental Defense Action Fund radio ad, 2008.
Now on the science: "I think climate change occurs, but the bulk of it is natural historic trends in climate. There is some suggestion that humans have caused some of it, but the answer is not a government, top-down scheme." _ WHO radio interview, April 1, 2011.
Now on the policy: "What I concluded subsequently is it is really a bad idea. It is ham-fisted. It is going to be harmful to the economy." _ South Carolina debate, May 5, 2011.
Then: "I started by saying let's stipulate that it is probable global warming is going on, and that it is conceivable human beings have a role, and therefore as a matter of prudence we ought to have less carbon loading of the atmosphere." _ New York Times interview, Nov. 13, 2007.
Now on the science: "I distinguish `science' from `political science,' and when I see 6,000 scientists sign something, that's called political science. That's not science." _ The Macon Telegraph, May 14, 2011.
Now on the policy: "It is inconceivable that any threat from global warming is big enough to justify destroying the American economy." _ The Macon Telegraph, May 14, 2011.
Then: Speaking of a regional cap-and-trade pact for power plant emissions, "This is a great thing for the Commonwealth (of Massachusetts). We can effectively create incentives to help stimulate a sector of the economy and at the same time not kill jobs." _ The Boston Globe, Nov. 8, 2005.
Now on the science: "He believes the climate is changing but he does not know the extent to which human activity is contributing to it." _ Romney spokeswoman Andrea Saul, May 18, 2011.
Now on the policy: "Gov. Romney opposes cap and trade because it is bad for business and it costs jobs." _ May 18, 2011, Andrea Saul.