You have to give New York Attorney General Eliot Spitzer and his friends an A for ambition. A few weeks ago Spitzer and the attorneys general of California, Connecticut, Iowa, New Jersey, Rhode Island, Vermont and Wisconsin, as well as the corporation counsel of New York, filed suit against five large electric utilities to force them to reduce their greenhouse gas emissions. Having battled teenage smoking and Microsoft, the attorneys general are now fighting global warming.

Well, not really. The main thing this suit might produce is publicity for the people who filed it. Even an amateur lawyer must suspect the suit's legal grounds are weak. The news release says that the case was filed in federal district court "under the federal common law of public nuisance, which provides a right of action to curb air and water pollution emanating from sources in other states. Public nuisance is a well-established legal doctrine that is commonly invoked in environmental cases." In other words: The utilities haven't broken any existing law; the attorneys general hope to create "new law" through a judge's decision.

But let's skip the legal niceties. If the suit succeeds, could it have a meaningful effect on global warming? The answer is "no." Again, skip legal niceties. Suppose, just for fun, the court simply shuts down the 174 fossil-fuel-burning power plants owned by these utilities (the American Electric Power Co., the Southern Co., the Tennessee Valley Authority, Xcel Energy Inc. and Cinergy Corp.). That's about 650 million tons of annual carbon dioxide (CO2) emissions, say the attorneys general. We'll ignore the economic consequences.

Now do the arithmetic. The attorneys general say these companies produce 10 percent of total U.S. CO2 emissions. Well, the United States generates about 25 percent of global greenhouse gases. So the net result is, at best, a 2.5 percent cut in annual worldwide greenhouse emissions. The entire cut would be offset in a few years by normal world economic growth, which -- requiring more power -- results in more emissions. Global emissions are now rising about 2 percent annually.

The only way to reduce them sharply is to have a worldwide cooperative plan to do so. The Kyoto protocol, negotiated in 1997, was one plan. But it would not have actually reduced greenhouse emissions. They would have continued rising even if the United States had adopted Kyoto. Undermining Kyoto's effectiveness was the unwillingness of most developing countries -- prominently China and India -- to join. With mass poverty, they're more interested in faster economic growth than in slower global warming.

Their refusal was one reason the Senate would never have ratified Kyoto. In 1997 senators passed a resolution 95 to 0 disapproving the Kyoto approach. The other reason is that even modest reductions in U.S. greenhouse gases might result in higher energy prices, more regulations, slower economic growth or all three.

It's easy to be against global warming but not easy to be for the things that might control it. Barring some magical technological breakthrough, lowering U.S. emissions would require some or all of the following: tougher regulation or higher gasoline prices to force drivers into smaller and more fuel-efficient vehicles; restrictions on coal-burning power plants; encouragement of nuclear power; expansion of drilling for natural gas and more imports of liquefied natural gas; and regulations or tax penalties to discourage large homes.

No judge should try to impose new policies. These issues belong in the political arena, not the courts. But even if the United States embraced tough anti-global warming policies -- and other industrial countries did the same -- the effect would be offset unless developing countries joined. The Intergovernmental Panel on Climate Change has projected that greenhouse emissions will more than triple over the next century under "business as usual" assumptions. Virtually all the increase occurs in developing countries.

Spitzer and his allies can't change any of this. Their suit mainly allows them to advertise themselves to people who don't know better. Here's Connecticut Attorney General Richard Blumenthal sounding off:

"Our lawsuit is a huge, historic first step toward holding companies accountable for these pernicious pollutants that threaten our health, economy, environment and quality of life now and increasingly in the future. The eventual effects . . . [will be] increasing asthma and heat-related illnesses, eroding shorelines, floods and other natural disasters, loss of forests and other precious resources."

Actually, this contains considerable distortion. In truth, no one knows how much the world will warm, exactly when or with what consequences.

Any self-respecting judge will dismiss this suit -- and do more. Because the only point is political self-promotion, the judge ought to require the attorneys general to pay court costs and defendants' costs from their own pockets. There's a name for what the attorneys general are making of themselves: a public nuisance.