Sunday afternoon is not the best time to break news. Monday morning is when the EPA’s proposed rules for greenhouse gas emissions from existing power plants will be officially unveiled by EPA Administrator Gina McCarthy. But federal agencies leak like a sieve, and so we learned Sunday what the outlines of the rules will be: CO2 emissions from existing power plants will have to be cut by 30 percent from 2005 levels by 2030.

Environmental activists are not overwhelmed with joy at the news, although they remain hopeful that the final rules will be significant. The target is a little weaker than they want, and they say the battle to strengthen the rules during the coming public comment period will be immense.

“It’s a good first step, and only the proposed rule,” says Tyson Slocum, director of Public Citizen’s energy program. “We’ll submit comments pushing for a stronger standard.”

The Natural Resources Defense Council agrees. “The key will be how they solicit comments on more ambitious targets,” says David Hawkins, NRDC’s director of climate programs. “We need an open mind on their part to consider evidence we can do better.”

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Environmental experts generally agree that more ambitious targets are possible, especially if the EPA is going to make the rules extend all the way to 2030. Since technologies to produce energy more cleanly keep getting better and cheaper, the targets should grow significantly more ambitious over the course of the next decade.

“We’ll be pushing for 2020 reductions of at least 35 percent below 2005 levels, ramping up to more ambitious targets later in the decade,” says Hawkins.

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As we recently predicted, the EPA’s plan follows the broad contours of the NRDC’s proposed model: Each state will get a cap of allowable emissions and have options for how to meet it. The Washington Post’s Juliet Eilperin and Steven Mufson report that states will be able to use four different approaches: “energy efficiency, shifting from coal to natural gas, investing in renewable energy and discounts to encourage consumers to move to off-peak hours.” This flexibility is designed to allow states to meet the target without impeding economic growth or causing electric rates to skyrocket by just immediately closing a bunch of coal plants.

We are left, of course, with more questions than answers until further details come out. But the most important thing is the target. Environmentalists say the target is about what they were expecting. That might sound strange, since The New York Times had previously reported a target of a 20 percent reduction from current emissions. But that’s actually roughly the same as a 30 percent cut from 2005 levels.

The reason is the baseline. As The Wall Street Journal explained on Thursday, the baseline year that EPA uses is key, because emissions fell 12 percent between 2005 and 2012. The recession of 2008 significantly reduced emissions by slowing economic activity, and the fracking boom has since decreased CO2 emissions further by replacing coal with less carbon-intensive natural gas. “The utility industry would like to work from a baseline set between 2005 and 2007 because those years were the highest ever for U.S. carbon emissions,” the Journal reported. “Emissions started falling in 2008, so using a more recent time frame would set more aggressive carbon-reduction targets.”

As of last week, according to the Journal, “multiple industry executives have said the administration isn’t considering a base year of 2005, which is what most coal and utility companies had wanted.” But they were wrong. The EPA is actually giving them the baseline year they want, but with a 30 percent reduction rather than the previously reported 20 percent, so industry will still be sure to attack these rules as economically devastating. Of course, they would attack the rules no matter what. The dirty energy industry is a notorious bunch of whiners who constantly claim that any proposed environmental regulation will be more onerous than it actually turns out to be.

The big question on the minds of many environmentalists is whether this will be enough to encourage other major polluting countries to make significant climate commitments. While the CO2 reduction will be significant by historical U.S. standards, it won’t get emissions down anywhere close to what’s needed to avert catastrophic global warming, nor even get the U.S. to the goal it agreed to at U.N. climate talks in Copenhagen in 2009: a 17 percent reduction in greenhouse gas emissions from 2005 levels by 2020. The hope is that it will signal enough progress to get the rest of the world to agree to binding emissions reductions in the next round of U.N. climate talks, which is supposed to culminate in a new climate treaty signed in Paris in December 2015. Will these proposed rules be good enough? “[We’re] not exactly sure yet what the optimal target would be,” says Slocum. “It kind of depends if this rule can directly lead to binding cuts by China.”

The New Republic’s Jonathan Cohn lays it out clearly: “The Administration has said its goal is to reduce greenhouse gas emissions by enough to meet targets that President Obama set in 2009, just before international negotiations in Copenhagen. … The targets that the media outlets are reporting would fall short of that goal. Although experts and environmental groups have stated publicly they believe the U.S. needs to reduce power plant emissions by 25 percent to hit the Copenhagen targets, that was 25 percent from current levels — not 2005.”

But, as Cohn explains, there are still more options for meeting that Copenhagen goal: “The President’s Climate Action Plan, which laid the template for this new regulation, also called for other actions to reduce greenhouse gas emissions. In theory, they would offer other opportunities for the U.S. to hit the Copenhagen targets, even if the coming power plant rules don’t get the U.S. all the way there.” For example, if the EPA issues rules to clamp down on methane leakage during the drilling and transporting of natural gas, that would provide significant additional reductions in greenhouse gas emissions.

It’s also important to remember that this is just the beginning of the process of making these rules, not the end. As Cohn notes, the EPA may offer a range of options with different emissions targets, since this is only an initial proposal for stakeholders to bicker over.

Over the next year, environmentalists will have to fight to ensure that the rules will be strong enough to grant the U.S. the credibility to forge a new international climate agreement in Paris in 2015.