A new global warming treaty would be all economic pain and little environmental gain for America even if China and other fast-developing nations sign on as well. But if developing nations remain exempt, it would be all economic pain and no environmental gain. Either way, America should stay out. At the United Nations' Conference on Climate Change in Copenhagen in early December, proponents of the 1997 Kyoto Protocol — which expires in 2012 — will try to hash out a new international agreement for lowering carbon dioxide and other greenhouse gas emissions. In other words, a new glo-bal energy tax may be in the works.

The United States did not ratify the Kyoto Protocol, and for good reason. Its provisions would have cost U.S. consumers trillions, while having virtually no impact on world temperatures.

Nonetheless, many in the international community want to finalize stringent new post-2012 provisions at Copenhagen. They have also expressed optimism that the Obama administration will join in such an agreement.

However, the United States should follow the policy set out in the Senate's 1997 Byrd-Hagel resolution and not enter into any global warming treaty that harms the American economy or leaves out major developing nations. The resolution passed 95-0.

Despite that unanimous resolution, then-Vice President Al Gore led the American delegation to Kyoto and agreed to a treaty that violated both provisions.

President Clinton never submitted it for Senate ratification, knowing full well that he could not possibly get the two-thirds' support needed for a treaty that so flouted Byrd-Hagel. Neither did President Bush. Nor has President Obama.

The Byrd-Hagel resolution remains in effect and still provides sound advice as we head into discussions about a post-Kyoto treaty in Copenhagen.

The U.S. Energy Information Administration projected costs of U.S. compliance with the Kyoto treaty at between $100 billion and $397 billion annually. Any serious new agreement in Copenhagen would likely be far more expensive.

Proponents of Kyoto described its 5 percent greenhouse gas emissions reduction targets as a "modest" step. Now, they say, much tougher — and costlier — provisions are necessary. The Byrd-Hagel provision prohibiting economic harm would clearly be violated.

The other provision — that China and other developing nations must commit to emissions reductions — is also very important. The Byrd-Hagel resolution warned that "greenhouse gas emissions of developing country parties are rapidly increasing and are expected to surpass emissions of the United States and other (developed) countries as early as 2015." Turns out, that was a Pollyanna-ish projection. Emerging nations' emissions began to outpace the developed world's in 2005. They are projected to continue increasing seven times faster than in the developed world. China alone now out-emits the United States. Its emissions growth through 2030 is projected to be nine times higher than ours. Yet China insists on keeping its exemption from emissions reduction obligations, regardless of what America does.

Any reduction in emissions from the U.S. and other developed nations would be swamped by growing emissions from developing nations — even more so if developed-nation constraints shift economic activity to exempted nations.

Any proposed solution to global warming makes sense only to the extent global warming is a serious problem in the first place, and there is growing reason for doubt. Indeed, since 1997 — the year of Kyoto — world temperatures have been remarkably flat.

The lack of global warming won't stop global warming activists in Copenhagen, but it should stop the U.S. government from embracing an ineffective solution to an overstated problem.

Ben Lieberman is a senior policy analyst at the Thomas A. Roe Institute for Economic Policy Studies at The Heritage Foundation. This essay was distributed by McClatchy Tribune News Service.