WASHINGTON Carbon-capping legislation moving through the U.S. Congress gives a sign to world climate-watchers that the United States is serious about crafting an international deal on global warming in December.
* Armed with Friday's vote in the U.S. House of Representatives to approve a plan to limit emissions of the greenhouse gas carbon dioxide, President Barack Obama heads for July meetings in Italy of the Group of Eight industrialized nations with added credibility on the climate issue.
Obama's election last year boosted U.S. standing among international climate negotiators, after eight years of the Bush administration, which opposed any economy-wide, mandatory moves to limit greenhouse pollution.
Climate change is a top Obama priority and part of his plan for an environmentally friendly economic recovery.
* U.S. legislation, such as the so-called Waxman-Markey measure approved by the House, signals to international climate negotiators that the United States is ready to make a commitment to reduce its emissions of climate-warming carbon, which could spur other big emitters -- Europe, China, India, Brazil and Mexico, among others -- to do the same.
These countries are part of the Major Economies Forum, a group of the world's biggest greenhouse polluters, which will gather on the fringes of the July G8 meeting.
* These negotiations are aimed at a December climate meeting in Copenhagen, when diplomats will aim to craft a new agreement on limiting climate-warming emissions to replace the 1997 Kyoto Protocol, which runs out in 2012.
A U.S. domestic commitment could be enough to get world negotiations on track for that meeting. After House passage, any climate measure has to be approved by the U.S. Senate, which is a tougher challenge, and then the two versions of the bill must be reconciled before being signed into law. There is no certainty this could be completed this year.
The U.S. legislative timetable could work to Washington's advantage in Copenhagen, giving climate diplomats room to maneuver in international talks.
* Negotiators do not want to see a reprise of the U.S. response to the Kyoto Protocol, which was negotiated by diplomats and signed by President Bill Clinton, but never ratified by the Senate. The United States is now the only major industrialized country not to join this pact.
A signed-sealed-and-delivered U.S. climate change law would be positive but not necessary to show the international community Washington's credibility on this issue, said Robert Stavins, an environmental economist at Harvard University.
"Those who are astute recognize the importance of commitment by the U.S. that has the greatest credibility is not our signing an international agreement; it is putting in place domestic legislation," Stavins said. "That's what's binding."
(Editing by Jackie Frank)