The warning sounded often as Congress weighed legislation to curb carbon dioxide and other greenhouse gases a few years ago: Take action, or the federal Environmental Protection Agency will pick up the task. Lawmakers faltered, and now the agency is moving forward, bolstered by the approval of the courts. The most recent ruling arrived Tuesday, a three-judge panel of the U.S. Court of Appeals of the District of Columbia unanimously upholding the agency finding that greenhouse gases endanger public health.

The agency started down this path in 2007, after the Supreme Court ruled the EPA was required to pursue regulation under the Clean Air Act — if it concluded that heat-trapping emissions put public health at risk. In 2009, the agency reached that conclusion. It since has proposed new fuel-economy standards for cars and trucks, with the overall goal of 54.5 miles per gallon by 2025.

The EPA also has put forward limits on greenhouse emissions from new power plants.

Not surprisingly, the activity triggered a lawsuit, a collection of states and industry groups seeking to block the agency. That case led to the ruling this week. The appeals court proved emphatic, arguing that the agency was “unambiguously correct” in moving ahead to limit emissions from motor vehicles and power plants.

The lawsuit challenged the agency’s conclusion that greenhouse gases “threaten the health and welfare of current and future generations.” In doing so, it took aim at the underlying science of climate change. The court pointed to the “substantial record evidence” that greenhouse gases are warming the planet. More, it stressed: “This is how science works,” adding that the agency “is not required to reprove the existence of the atom every time it approaches a scientific question.”

Assessing the limits for car and truck emissions, the court determined that the rule was “neither arbitrary nor capricious.” The court also let stand the agency’s “tailoring rule,” a reasonable bid to set priorities in addressing emissions, focusing on the largest sources rather than chasing down the vast range and number of smaller sources.

All of this provides a bright green light for the agency to proceed. Of course, Congress still could act, if not through a system of cap and trade, then perhaps via a carbon tax, both routes employing market incentives to curb emissions.

The need for action clearly mounts. The journal Nature Climate Change reported this week on sea levels rising much faster than projected along the East Coast, reflecting, in part, accelerated melting in the Arctic. The EPA relied on the evidence. So did the appeals court. Might Congress follow?