Climate activists focused their criticism on developed nations. Kumi Naidoo of Greenpeace said the U.S., in particular, was a stumbling block to the negotiations.
The Obama administration has already taken some steps to rein in emissions, such as sharply increasing fuel efficiency standards for cars and trucks and investing in green energy. But a climate bill that would have capped U.S. emissions stalled in the Senate.
In a message to the conference, U.S. Sen. Barbara Boxer said "there are leaders in Congress who understand the urgent threat facing the globe, and we are dedicated to preventing the terrible impacts of unchecked climate change."
Her message contrasted with that of another U.S. senator, Republican Jim Inhofe, who spoke in a video recording shown at the side event in Doha with climate skeptics. Calling global warming a "hoax," he said the focus of the Doha conference was not the environment, but "spreading the wealth around."
In 2010, a survey of more than 1,000 of the most cited and published climate scientists found that 97 percent of them believe climate change is very likely caused by the burning of fossil fuels.
"It's getting harder and harder to be a climate denier as the evidence of climate change grows," said Michael Oko, a spokesman for the World Resources Institute, an environmental think tank. "Fortunately, I'm sure the negotiators here won't let this take away from what needs to be done to address this global challenge. We need more solutions, not distractions."
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