IN HIS second inaugural address, President Obama promised to do more about climate change. Now, five months later, he has explained what he meant.

The president missed his chance to pass a major climate bill when Democrats ruled Capitol Hill in his first term; since then, Congress hasn’t been able to agree that global warming is a significant problem. On Tuesday Mr. Obama unveiled a Plan B policy that bypasses Congress’s gridlock, relying on powers the executive already has.

A lot of attention focused on the president’s insistence that the fate of the controversial Keystone XL oil pipeline rests on whether the project would result in significant net carbon dioxide emissions. This could be good or bad news for anti-pipeline activists, since the alternatives to pipeline transportation involve moving crude by rail, barge or truck, and studies have concluded that the emissions impact of various scenarios would be minimal.

Besides, the president is making far more important determinations than the future of a single oil pipeline. Mr. Obama on Tuesday ordered the Environmental Protection Agency (EPA), which has delayed rules to limit carbon dioxide emissions from new power plants, to finish them by September. He also commanded the EPA to get to work on regulating existing plants, the largest source of greenhouse emissions, in conjunction with states and with attention to avoiding unnecessary costs.

Though these rules will presumably apply to many different kinds power stations, the EPA will probably aim its new restrictions at the very dirtiest — those that burn coal, spewing a toxic mixture of gases and particles into the atmosphere in the process. There are a variety of reasons to phase out widespread coal burning, having to do with public health and environmental protection. And now that cleaner-burning natural gas — coal’s obvious substitute, for the moment — is far less expensive and far more plentiful in America than it used to be, the costs of reducing coal use are lower. If Mr. Obama gets all of these EPA rules through, it would be a significant accomplishment.

The president also wants Americans to waste less energy, by requiring heavy-duty trucks to burn less fuel and appliances to use less electricity, and he wants to reduce emissions of other potent greenhouse gases such as methane, which can leak during natural gas extraction and transportation.

Mr. Obama’s plan is far from perfect. For one thing, it excludes the best anti-emissions policies, such as carbon taxes, that all require Congress’s approval. For another, it appears the EPA’s new rules on existing power plants could take a very long time to write and implement. The president has also larded up his plan with some of the usual nonsense that poses as energy policy in Washington, such as $8 billion in loan guarantees for fossil fuel technologies like carbon capture and sequestration, which hasn’t proven to be anything but excessively expensive. And the country still requires a long-term strategy to green the economy.

But the major elements of the White House’s plan are still far better than settling for congressional inaction. Republicans in Congress, who were swift to criticize Mr. Obama on Tuesday, should offer him a better way to reduce emissions meaningfully while minimizing the economic effects. Otherwise, it’s time for the president to follow through.