LAST WEEK, as the nation’s attention was on the Supreme Court and health care, the U.S. Court of Appeals for the District of Columbia Circuit issued a ringing ruling concerning America’s response to global warming that does two critical things. First, it emphatically dismisses arguments that the science is too uncertain to justify federal action. Second, it assures Congress that, if lawmakers don’t act on global warming, the courts won’t stop the Environmental Protection Agency (EPA) from doing so independently of Congress, using the powers the EPA has under the Clean Air Act. Both should persuade lawmakers to develop, at long last, a comprehensive response to climate change instead of leaving the job to the EPA’s command-and-control regulation.

In 2007, the Supreme Court — in Massachusetts v. EPA — ruled that the Clean Air Act required the EPA to determine whether it must regulate greenhouse gases as it does more familiar air pollutants, such as the gases that form smog. Following these orders, the agency determined shortly thereafter that it must, and it began the process of writing rules that hit some of the nation’s largest emitters, such as coal-burning power plants. In response, dozens of these companies sued, arguing that the EPA had overzealously interpreted the law and had relied on uncertain science.

In a wide-ranging decision, the D.C. Circuit rejected those claims. The judges were most powerful when they discarded arguments that the EPA improperly relied on outside studies that were inadequate to declare human activity the “root cause” of dangerous climate change. The ruling describes a “substantial” case for concern about human-induced global warming that the EPA amassed.

Of course, there is an inevitable amount of uncertainty. But there is enough evidence to justify action, and the judges were right to uphold the EPA’s reading of the science. “EPA simply did here what it and other decision makers often must do to make a science-based judgment,” they wrote. “This is how science works. EPA is not required to re-prove the existence of the atom every time it approaches a scientific question.”

Now that the D.C. Circuit Court has slammed the legal challenge to the EPA’s regulation of greenhouse gases, the agency is clear to continue clamping down on emissions. Under the Clean Air Act, that means a command-and-control approach that will be expensive but won’t reduce emissions enough. Congress has only one reasonable option to avoid that far-from-optimal outcome: enacting a more effective and efficient policy such as a carbon tax or a cap-and-rebate program that complements or preempts the EPA’s regulation. Lawmakers have ignored the problem for far too long.