When Al Gore was in the White House, global warming was a disaster of the first order. Republican presidential candidates are now saying it is anything from a fraud to trivial.

Both sides claim sound science, and both are wrong. In politics, “sound science” means whatever supports your preconceived positions.

For American voters, climate change is an issue offering lessons in how to reject political nonsense on the extremes, and find the middle. If we can’t find the middle of a generation-long concern like climate change, one where modest steps are sufficient for the moment, how will we ever tackle immediate issues such as jobs, debt and the looming retirement of the Baby Boomers?

First, here are the positions of Republican presidential contenders Mitt Romney and Rick Perry. (Herman Cain has not taken a position on climate change.)

Last June, Romney said in New Hampshire: “I believe based on what I read that the world is getting warmer” and that “humans contribute to that.” In New England, voters of both parties tend to support environmental protection. Romney’s June statement is similar to what George W. Bush said when he was president.