(Ahem.) Wereallyneedacarbontaxorcapandtradebutintheabsenceofsufficientpoliticalwillweshouldturntootherpollitically-viablealternativesfortheshortandmediumterm.
Okay, with that out of the way, here's the basic idea for the US: natural gas eats coal's lunch but renewable power gets a guaranteed and growing share of the power market. More specifically, natural gas interests support a national Renewable Portfolio Standard guaranteeing an increasing market share to renewables, with some state-level flexibility to make it meaningful and feasible in most states. In return, enviros let better-regulated fracking expand. The deal might need two add-ons: gas interests support legislation limiting coal exports, and in return, more areas get opened, carefully, to fracking (looking at you, California).
I'm not certain we need a deal on coal exports - enviros can try their luck fighting coal export terminals and rail lines on their own without the help of national legislation. Coal exports to Europe would also fall under Europe's cap, so I could see it being Europe's problem to decide how they'll meet their cap. I also think it's usually better to determine that emissions are caused by the country that emits them, not by countries upstream or downstream in the production chain. On the other hand, this deal is less useful if the coal still gets burnt but in another country. If enviros demand assistance in limiting coal exports though, then they have to offer something in return.
This would be a temporary alliance between natural gas and renewables. After a decade or so of growing renewables and decreasing coal, natural gas would have to start phasing in carbon sequestration and would likely have to be phased out itself. That's a fight in the future, though.
Enviros could turn down this deal, but I'm not sure the present status is better, with fracking sucking up the large scale funding that might otherwise be available for renewables.
