Brad Johnson of ThinkProgress has a nice chart showing all the ways in which Kerry and Lieberman's Senate climate bill differs from the bill the House passed last June. All told, the two bills are surprisingly similar, but I'd say the most significant differences are these:

--The Senate bill refunds a greater share of the proceeds from selling carbon permits back to consumers—75 percent versus 45 percent in the House bill. Much of this rebate comes in the form of electric utilities getting free permits and passing on the savings to consumers; I explained the logic behind that move here.

--The Senate bill exempts manufacturers from cap-and-trade until 2016, so in this sense it's a little weaker on pollution targets.

--The Senate bill has more support for nuclear power, natural gas vehicles, and offshore drilling. That's a consequence of trying to get 60 votes.

--The Senate bill is a lot weaker on renewable energy mandates and efficiency standards. In fact, it's worth reiterating that the Senate bill's renewable targets would do less (yes, less) than what we could expect to happen if no bill passed at all. If environmental groups want to strengthen the bill, this is, far and away, the most promising place to do so, especially since these items will make a big difference in the short term.

--The Senate bill has much stricter provisions for overseeing the carbon markets—prohibiting derivatives and preventing anyone who's not a covered polluter from buying permits under a cap-and-trade system. (As I've reported before, there's a case to be made for allowing derivatives in a cap-and-trade system, but right now, there's so much hostility toward Wall Street—just look at how financial regulation got strengthened in the Senate—that this sort of crackdown is inevitable.)

--The Senate bill has some interesting transportation provisions which I'll explain in another post. Basically, there's $7 billion a year for smart growth funding. Given that urban planning has to be a part of any comprehensive climate policy, this looks like a major improvement over the House bill.

--The Senate bill allows the EPA a little more leeway to set its own standards for power plants under the Clean Air Act. I'm not sure yet how this plays out in practice, but a lot of green groups are worried that a climate bill would "gut" the EPA's existing greenhouse-gas authority, and it's worth noting that the Kerry-Lieberman bill does a little less gutting here.