Obama's push to reduce coal use has two parts.
Decrease domestic coal use by limiting carbon emissions at power plants. Again: This is the most important part of Obama's speech, bar none. If he dropped everything else in his plan, this idea would still warrant a significant amount of attention, both here and abroad.
That said, what Obama is announcing today is not an immediate limit to how much carbon pollution coal-burning power plants can emit. During his State of the Union address, the president told Congress that if it didn't act to curb carbon emissions, he would do so. Which in a way was like a kid loudly announcing that he had decided to do his chores. You see, Obama is legally mandated to act on curbing carbon emissions, following a court's determination that carbon dioxide is a pollutant. The EPA has been expected to develop a new limit on emissions for years, but, so far, only a proposal to limit emissions from new coal plants had been proposed. A lawsuit hoping to force the agency to act was postponed last week once it became apparent that Obama planned to finally tackle the real problem: existing plants.
What Obama is announcing today is a timeline for setting that standard. Specifically, he is asking the EPA to work with states and stakeholders for a proposal by next June and a final rule by June of 2015. (He also hopes that the rule for new plants will finally be finished by this September.) Meaning that, if everything goes right, we could have an as-yet-unspecified reduction in carbon dioxide emissions from coal-burning plants in only two more years.
This is good. It is also terribly belated. When Barack Obama took office, the level of carbon dioxide in the atmosphere was at about 387 parts-per-million — the highest they'd ever been. Since, the trend has only increased; we've recently passed 400 parts-per-million. While America's carbon dioxide emissions have fallen since then (thanks to the factors named above), we are still produce more carbon dioxide per person than almost any country. By 2015, it will be hard no to lament the six years during which Obama was empowered to act unilaterally but didn't.
Assuming that the new rule goes into effect in 2015. Energy companies and businesses will almost certainly challenge any rule. And the court ruling that give the EPA the power to act is itself being challenged, which could throw a major wrench into the effort.

A new poll from Pew Research indicates that Americans consider global warming the sixth-greatest threat. On the whole, the world ranks it first. (Darker colors indicate higher rank.)
Decrease international coal use. That 400 parts-per-million figure, of course, includes the entire world's carbon emissions, something over which the president has limited control. This has long been a hobbyhorse of opponents of action on climate change: Why should we act when China, the world's largest carbon emitter, isn't?