All told, the draft Senate climate bill that John Kerry and Barbara Boxer unveiled today looks awfully similar to the Waxman-Markey bill that passed the House back in June. Everything you've read about that earlier bill, griping and cheering alike, basically still applies. Plus, lots will change as this bill shimmies its way through at least five different Senate committees, so there's no use pretending this is a final product or anything. Still, there are a few differences between this Kerry-Boxer draft and the House bill that are maybe of interest and worth highlighting:

Slightly more ambitious targets: Most notably, the Kerry-Boxer draft aims to reduce CO2 emissions 20 percent below 2005 levels by 2020. The House bill called for a 17 percent cut. (Note that, thanks to the recession, we'll be 8.5 percent below 2005 levels by the end of this year, which is why Boxer stumped for a steeper reduction.) Note that even this new goal is flimsier than the cuts the IPCC has recommended to give us a fighting chance of preventing more than a 2ºC rise above pre-industrial levels. (Think 25 to 40 percent below 1990 levels by 2020.)

Shhhh on calling it "cap-and-trade": The Kerry-Boxer draft, in a spate of euphemistic goofiness, has decided to dub its cap-and-trade system for greenhouse gases a "Pollution Reduction and Investment system." Valiant attempt at reframing, sure, but I can't imagine it'll catch on. By the way, at their press conference today, Boxer and Kerry took pains to stress that the cap would cover less than 2 percent of U.S. businesses—only the big polluters that account for 75 percent of the country's emissions.

A price collar on carbon permits: The Kerry-Boxer draft includes a "price collar" for its cap-and-trade program. Read Joe Romm for a fuller explanation, but the rough concept is that there are mechanisms to try to prevent the price for carbon permits dropping below $11/ton or soaring above $28/ton initally (with the floor and ceiling rising each year). In theory, this will limit price volatility, which can make it trickier for companies to make investment decisions. One of the virtues of a carbon tax is predictability, so a price collar inches the cap-and-trade somewhat closer to that ideal.

But who gets the permits? Who knows? Recall that the biggest brawls during the House mark-up were over which industries got free pollution allowances under the cap-and-trade system. (I broke down where they all went here—utilities made out very well, oil refiners got squeezed, but all told it wasn't a total debacle.) Boxer and Kerry have left this contentious part of the bill blank. A big, glaring TK. Odds are, Max Baucus's Finance Committee will have a strong say in filling this in.

Natural gas gets some love: The Kerry-Boxer draft will have a new federal program to encourage natural-gas production and use. As I've noted before, a climate bill, depending on how it gets crafted, could be a boon for the natural-gas industry, especially if a lot of electric utilities switch from coal to natural gas (which produces about half the CO2). But the House bill gave utilities ample incentives to keep burning coal, in the hopes that carbon-capture tech would soon come along. The natural-gas lobby is starting to hurl its weight around to try and shift this dynamic.

More scrutiny for offsets: By now, you've heard my tirade against carbon offsets. The happy news is that the Kerry-Boxer draft tries to reduce the number of international offsets available to polluters (these are often the most dubious ones). Plus, as Victor Flatt explains, Boxer and Kerry appear to want to subject offsets to more rigorous scrutiny and accounting. Let's hope this survives the Senate sausage grinder, because this looks like a hugely positive step.

What about China and India? The Kerry-Boxer draft leaves open how to deal with China, India, and other developing countries. Remember, the House bill imposes a mandatory carbon tariff on imports from countries that don't adopt their own climate programs by 2020. It's unclear how the Senate will deal with this question.

EPA still gets to wield the ax, if necessary: In another departure from the House bill, the Kerry-Boxer draft preserves the EPA's authority to regulate large sources of greenhouse gases on its own. (The House bill would essentially supersede EPA authority.) This is something a lot of environmentalists have been fighting to protect.

A crack down on carbon speculators: The Kerry-Boxer draft tries to buck up oversight over carbon-trading markets. In the House bill, regulatory authority is shared: FERC handles the cash market and the Commodity Futures Trading Commission handles derivatives (this was done at the request of farm-state senators). Boxer and Kerry want to have the CFTC oversee both markets, and give regulators more power to tamp down on "excessive speculation."

Stricter scrutiny for biofuels: Remember when Collin Peterson convinced Waxman and Markey to stop the EPA from considering the indirect land-use effects of biofuels, especially deforestation, in the House bill? The Kerry-Boxer version has no such language, at least not yet—though farm-state senators will have plenty of opportunity to shill for ethanol.

Greener taxis, more public transit: As Elana Schor reports, the Kerry-Boxer draft may provide more money for mass-transit programs and bike paths. It also requires states to use a certain percentage of carbon funds for green-transportation programs, whereas the House bill only "allowed" states to do so. Interestingly, the Senate draft also allows states to set higher fuel-economy rules for taxis, which produce a disproportionate share of vehicle emissions.

Not tough enough on methane? The House bill had strict regulations on methane emissions from landfills, coal mines, and natural gas pipelines, but the Senate draft appears to allow these sources to voluntarily capture methane in exchange for carbon offsets, at least until 2020. That seems pretty unwise, given how potent methane is as a greenhouse gas.

I'll add more if I see more. And, per the caveat emptor above, this is just the initial draft. The legislative process can get messy, and attracting 60 votes in the Senate will likely require compromise after compromise after compromise. Expect a lot to get jostled around.