Just for starters
Your friends at the Petroleum Institute and the GOP could buy one page ads in the WSJ and NYT saying something like
"We've been lying to you about this for years. We're sorry, but it seems we really do have a very serious problem on our hands, and we are at least partly responsible for it, or at least, responsible for trying to cover it up. We're willing to do whatever is reasonable to help set it straight."
This might go a long way to generating public interest and political will to do something about it.
And just think, your guys might even be able to write off the cost of the ad as a legitimate public relations expense.
And yes, that last para was no accident, any more than your continuous opposition to the entire idea of AGW has been merely scientific conservatism.