Small island nations under threat from rising sea levels have been pushing for some mechanism to help them cope with such natural catastrophes, but the U.S. had pushed back over concerns it might be held liable for the cleanup bill since it is the world's second-biggest emitter behind China.
The Doha deal doesn't establish that kind of mechanism, but says that countries agree to talk about it.
"It is a significant change in (the U.S.) stance and big unexpected outcome for Doha," said Iain Keith, senior campaigner with activist group Avaaz.
He said overall there was "subtle yet significant shift" in the U.S. position in the talks.
"Many parties will be disappointed that the U.S. didn't come here and offer more on finance," he said. "But with the fiscal cliff discussion in Washington, their hands are tied," he added, referring to the looming combination of automatic tax increases and U.S. government spending cuts early next year.
The Doha deal included vague language on how rich countries would scale up climate aid to $100 billion annually by 2020 — a goal agreed to three years ago. With budgets under stress from financial turmoil, developed countries resisted calls by developing countries to make firm commitments.
"I think in general donor countries with some exceptions were not in a position to put hard numbers on table for all sorts of reasons among them fiscal challenges that we are facing in the U.S. and Europe is facing," said Stern, the U.S. climate envoy.
In news conferences in Doha, the U.S. delegates stressed what the administration has already done: increased fuel efficiency standards for cars and trucks, worked to boost energy efficiency in buildings and invested in green energy.
Wael Hmaidan, a Lebanese activist and director of the Climate Action Network, said he was disappointed that the U.S. didn't offer more in Doha, especially on financing for poor countries.
"We were hoping there would be some kind of movement after the election," he said. "We knew there wouldn't be any major change but we hoped there would be more flexibility and room and this was not demonstrated."
Some may have overestimated how quickly Obama's comments on climate change would translate into action, said Jake Schmidt, of the Natural Resource Defense Council.
"Things take time to settle in the U.S.," he said. "But I think there's a growing sense that climate change is real, extreme weather is happening in the U.S. It shows up in all the polls."
Schmidt said the administration could achieve further emissions cuts with new standards on existing coal-fired power plants.
AP Environment Writer Michael Casey contributed to this report.
Ritter can be reached at www.twitter.com/karl_ritter and Casey can be reached at www.twitter.com/mcasey1