Last week the U.S. Supreme Court brought the reality of climate change to the foot-draggers and excuse-makers in the Bush administration and the conservative skeptics in the nation whom they serve.

In no uncertain terms, the court told the Environmental Protection Agency that the Clean Air Act had given it the "clear statutory command" to regulate four greenhouse gases, including carbon dioxide. The decision was decided by only a 5-4 margin, but it will sound like thunder to those who have been in denial about doing something serious about global warming.

The majority opinion, written by Justice John Paul Stevens, laid out the history and considerable scientific evidence surrounding the issue. It bluntly began: "A well-documented rise in global temperatures has coincided with a significant increase in the concentration of carbon dioxide in the atmosphere. Respected scientists believe the two trends are related ... ." Later in the opinion came another alarming truth: "The harms associated with climate change are serious and well recognized."

The case was initiated by a dozen states -- significantly including Massachusetts, with its coastline potentially threatened by rising sea levels -- as well as local governments and private organizations. They claimed that the EPA had abdicated its responsibility to regulate "any air pollutant" from new motor vehicles.

Two questions were central: Does the EPA have the statutory authority to regulate greenhouse gases in new vehicles? If so, are the agency's reasons for refusing to do so in accord with the law? Yes and no, the Supreme Court decided in favor of the plaintiffs, although they had lost earlier in a federal appeals court.

The EPA's "laundry list of reasons not to regulate" -- as Justice Stevens put it -- boils down to the familiar attitude of the Bush administration: Pay lip service to the idea that human activity contributes to global warming, but don't take concrete steps to do anything about it.

Whatever the EPA now decides to do, this victory for the environment may affect a number of court cases, including strengthening the hand of California, which is being challenged in court for setting its own tougher vehicle emissions standards. These rules have been adopted as a benchmark by 10 other states, including Pennsylvania.

Unfortunately, an end to the federal leadership vacuum on this issue seems unlikely. In reaction to the court's ruling, President Bush conceded that humans are contributing to greenhouse gases, but then attached conditions to EPA regulatory action: It must not impede economic growth and its environmental improvement must not be offset by the growing economies of India and China. It sounds like another excuse to do little with no sense of urgency -- when, in fact, the reality is long-term growth will be harmed if the United States does nothing.

At least the court said what had to be said loud and clear. It's past time all of America listened.