You might expect someone in my position, as head of an environmental group, to call for — to demand — a final international agreement to solve the global warming crisis at the Copenhagen climate conference in December. I will not. Signing a final treaty is not the only way Copenhagen can be successful.

[IMGCAP(1)]Let me explain. Environmental advocates like me have hungered for years to wrap up climate negotiations in December 2009 with a strong international deal. But instead of standing in the winner’s circle, it now looks like we’ll be on the final lap instead.

The U.S. negotiating team faces a specific challenge in preparing for Copenhagen. In the 1990s, the administration tried negotiating a climate treaty first and then used the signed treaty to leverage Congress to act. The Senate sent a strong signal that it didn’t like that approach.

Today, U.S. negotiators haven’t forgotten what happened in the ’90s. They have said for months that when it comes to binding emissions limits, the United States will not go where Congress has not gone first. That’s the right decision. In the absence of Senate action, it would be reckless to sign a final agreement this year with voluntary or non-binding caps, because such an agreement won’t protect the planet and could damage prospects for bringing the U.S. itself under a cap.

We’ll get a strong final agreement only after the U.S. has enacted a firm cap on its own greenhouse gas emissions. And an agreement with firm, enforceable emissions caps is the only way to ensure that we actually reduce greenhouse gas pollution. Only such caps will remove the threat of disastrous global consequences of climate change and ensure that we can leave our children and grandchildren a world with a fair resemblance to the one we know. That means a fast track to real caps for all major emitters. We must move beyond intensity-based limits and project-based offsets.

Because the future is at stake, we must make sure that violations of emissions caps will have internationally agreed consequences. The nations that agree to reduce emissions must effectively police one another’s compliance.

Waiting until 2010 to complete an agreement on binding emissions reductions would be disappointing. But it wouldn’t make Copenhagen a waste of time. Far from it. There are many ways the conference can — and I believe will — be a success, even if the Senate does not pass a cap before the meeting. First, the runup to Copenhagen has already created a wave of momentum, as countries from Mexico to South Korea consider committing themselves to impressive new programs for reducing their own emissions.

Perhaps the single most exciting piece of news is the progress being made on the program called Reducing Emissions from Deforestation and Degradation. The REDD program would, for the first time, allow people who own forests to make money without chopping down trees. That’s significant because forest destruction, mainly in the tropics, has accounted for 12 percent to 20 percent of global greenhouse gas emissions. Compensating people for protecting forests instead of tearing them down will yield huge dividends — for the atmosphere, for biodiversity and for poor communities around the world.

Finally, our negotiators can help broker an agreement in Copenhagen on the key structural elements of a deal and a mandate for completing negotiations on an accelerated timetable.

There is no magical significance to having a final deal before midnight on Dec. 18, 2009. The atmosphere doesn’t care about signing ceremonies or photo opportunities. What the planet will remember is whether heat-trapping emissions are brought under control in time to avoid terrible consequences. That’s the North Star on which we need to fix our gaze.

Since U.S. legislation is vital to international success, how do we get there? Simply put, Congress needs to finish what it’s started. With leadership from President Barack Obama, a core of dedicated House and Senate leaders, and a broad array of environmental, business, labor, religious and other groups, I’m confident the Senate will pass a bill in the coming weeks and early next year the president will sign a U.S. cap into law.

With America leading the way, the entire developed world will join with their own binding, internationally enforceable emissions limits. The large developing countries, too, will begin to take steps to level off their emissions and start reducing them, as they make their own commitments. Getting all major emitters including the U.S. on board is crucial. If that means we high-five each other in 2010, and not in 2009 as we’d hoped, so be it.

Fred Krupp is president of the Environmental Defense Fund.