His critics back home have harped on how any international agreement won't be legally binding, and, to be sure, this agreement won't be, but President Obama hailed the deal on climate change hammered out in Copenhagen as a step forward.

"It will not be legally binding, but what it will do is allow for each country to show to the world what they are doing," Obama told reporters at a press conference in Copenhagen. "...[A] sense on the part of each country that we're in this together and we'll know who is meeting and who's not meeting the mutual obligations that have been set forth."

The agreement, Obama said, consists of a document that will include "concrete commitments" with regard to emissions reductions added by each country in an appendix; whether each nation meets its targets, Obama said, will be up for international analysis and review "similar...to what takes place when the WTO [World Trade Organization] examines progress or lack of progress" on trade issues.

So, however non-binding the agreement is, Obama did succeed in bringing China and India to the table for something. But, as Environmental Defense Fund President Fred Krupp put it in his group's reaction to the deal, it's up to the U.S. Senate to pass energy reform legislation if the U.S. is to lead by example on emissions reductions: "Today's agreement leaves the U.S. in control of its own destiny. We have always known that the path to a clean energy economy goes through Washington, D.C. ... A year from now we can be further ahead or further behind, and the Senate will make the difference."

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