Obama's new emission rules: will they survive challenges?

In those cases, 26 months passed between issuance of the first rule and the oral argument, and another four months to decision. Then the U.S. Supreme Court was asked to review it all. It refused to reconsider the endangerment finding, suggesting that new attacks would also fail. The Supreme Court did take up the narrow question of whether greenhouse gases could be regulated under the so-called "prevention of significant deterioration program," which requires permits for new or modified sources of air pollution. Here, too, the EPA interpreted the Clean Air Act to give itself some flexibility to deal with a problem - climate change - that was not appreciated when the statute was enacted.

Oral argument was heard in February, and a decision is expected any day. Meanwhile, the challenged rules all remain in effect.

Thus, barring a political earthquake, the states will be preparing their plans in 2015 and 2016. As the owners of older coal plants consider whether to retire them or upgrade them to meet new and emerging environmental standards, the threat of greenhouse gas regulation will be an overlay of uncertainty and possible large expense, on top of the burdens imposed by other new and proposed environmental regulations and the competition from natural gas. The net result is likely to be an acceleration of the retirement of existing coal-fired power plants.

In late 2015 in Paris, the United Nations will convene an international meeting at which negotiators will again try to develop a successor to the Kyoto Protocol. President Obama hopes he can go there armed with a vigorous program, giving the U.S. some moral authority to call on other major countries to take strong action; his new guidelines for fossil fuels are a centerpiece of that program. Whether this will be enough to persuade other countries is very much an open question, though some early signals from China are positive.

For the past decade, growth in global greenhouse gas emissions has been utterly dominated by China. However, the failure of the United States to control its largest source of greenhouse gas emissions - coal-fired power plants - is a prime excuse used by China and other developing countries for not limiting their own emissions more strictly. They will also continue to point out that the U.S. still has high per-capita emissions, remains the largest historic emitter, is a large importer of carbon-intensive goods made in the developing world, and has become a major producer of fossil fuels.

As for the question of whether the Obama administration's proposed greenhouse gas regulations will make a significant contribution to slowing global warming, the answer is: It will help, but not nearly enough. Ananalysis from Climate Action Tracker finds that the new plan is insufficient to meet the U.S. pledge of a 17 percent reduction in all greenhouse gas emissions by 2020, and by 2030 U.S. emissions would still be around 5 percent above 1990 levels - far higher than the levels required for the 2-degree C pathway that is needed to avoid the worst effects of climate change.

In sum, the new proposal is a hop in the right direction, but far short of the mighty leaps the world needs.