At the ongoing U.N. conference on climate change in Copenhagen, proponents of the 1997 Kyoto Protocol -- for which initial commitments expire in 2012 -- are trying to hash out a new international agreement for lowering carbon dioxide and other greenhouse gas emissions. In other words, a new global energy tax may be in the works.

The United States never ratified Kyoto, for good reason. Its provisions would have cost American consumers trillions, while having virtually no impact on world temperatures. In much the same way, a new global warming treaty would be all economic pain and little environmental gain for the American people.

Our government would be wise to adhere to the Senate's 1997 Byrd-Hagel Resolution. It passed 95-0 and made it clear that our government wouldn't enter into any global warming treaty that harmed the American economy or gave major developing nations a free pass on emissions. Indeed, America's strong environmental record demonstrates that free markets, rather than binding treaties, provide the more sensible way to address global warming.

Nonetheless, many in the international community want to finalize stringent new post-2012 provisions at Copenhagen, or at least initiate the process that would lead to such measures. They have also expressed optimism that the Obama administration would join in such an agreement.

Despite the Senate's unanimous -- and eminently reasonable -- support for Byrd-Hagel, Vice President Al Gore led the 1997 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 to ratify a treaty. Neither did President George W. Bush. Nor, for that matter, has President Obama. Byrd-Hagel remains in effect and still provides sound advice as we head into discussions about a post-Kyoto treaty in Copenhagen.

A U.S. Energy Information Administration study projected costs of U.S. compliance with the Kyoto treaty would be between $100 billion and $397 billion annually. Any new agreement brokered 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 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."

That prediction turned out to be Pollyannaish. Emerging nations' emissions have exceeded the developed world's emissions since 2005. They are projected to continue increasing seven times faster than those of the developed world.

China is of particular concern. It now out-emits the U.S., and 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.

In effect, any reduction in emissions from the U.S. and other developed nations would be more than offset by growing emissions from developing nations. And as constraints on developed nations shift more and more economic activity to exempted nations, the net increase in emissions will only expand.

With or without America or China, 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, world temperatures have been remarkably flat. "Climategate," the recent release of internal e-mails showing gross misconduct among many key scientific figures behind the putative global warming crisis, raises further questions that should be resolved before any new policy decisions are made.

However large or small a problem global warming proves to be, a growing body of evidence shows that free markets -- not binding treaties -- are the best way to deal with it. According to U.N. data, the U.S. reduced greenhouse gas emissions by 3 percent from 2000 to 2006. Of all the European and other developed nations that committed to reducing emissions under Kyoto, only France did better than that. That's right: America did better as a Kyoto treaty outsider than most treaty insiders.

There are reasons that explain this seemingly counterintuitive result. A sensible approach to global warming has to center on technological innovation, and in particular ways to produce and use energy more efficiently and with fewer emissions.

Innovation is the solution, and we know from long experience that free economies innovate better than centrally planned ones. However, a treaty with binding targets introduces a significant element of central planning and stifles innovation.

We also know that strong economies innovate better than weak ones, but these costly energy controls weaken economies. Perhaps most importantly, stable economies innovate better than unstable ones, especially for something like energy for which the investments often run into the billions of dollars and the payoffs play out over decades. But the experience with Kyoto is that its provisions add a significant element of instability.

Neither the lack of global warming nor Climategate will dissuade activists in Copenhagen from pursuing harsh levies on developed countries, but these points should stop the U.S. government from embracing an expensive, ineffective solution to an overstated problem.

Ben Lieberman is a senior policy analyst in the Thomas A. Roe Institute for Economic Policy Studies at the Heritage Foundation.