The highly charged debate on global warming reached the US Supreme Court Wednesday, prompting the justices to question the impact of auto and truck emissions on the environment, what must happen to rescue the world's coastlines, and whether the Environmental Protection Agency has to help stop the damage.

In the first case of its nature to reach the high court, the justices grilled both James R. Milkey, the top environmental lawyer in the Massachusetts attorney general's office, and Gregory G. Garre , the deputy solicitor general representing the Bush administration, on their views on global warming. The justices also probed the unsettled science of climate change and even weighed foreign policy considerations of the EPA setting limits on carbon dioxide pollution by new motor vehicles.

Supreme Court Justice Antonin Scalia set the tone for the sharp-edged debate when he interrupted Milkey barely two minutes into the hearing.

"When is the predicted cataclysm?" Scalia asked.

Global warming hasn't reached a cataclysmic phase, Milkey answered, but is in a stage of "ongoing harm," referring to warming temperatures leading to rising sea levels and erosion along Massachusetts' 200 miles of coastline and shores worldwide. Failure to limit greenhouse gases, he said, was like lighting "a fuse to a bomb."