The yearly UN conference on climate change ended on Friday with only modest results after delegates failed to establish a timetable for future cuts on pollution linked to global warming.
Despite nearly two weeks of meetings, which drew 6,000 participants to Nairobi from around the world, the delegates could not agree on a number of issues, especially how to move beyond the Kyoto Protocol, which requires cuts in emissions by most industrialized countries but expires in 2012.
Two persistent problems were US reluctance to agree to any mandatory emissions limits and increased stubbornness by China and India -- two of the world's fastest-growing polluters -- which face no penalties under the Kyoto agreement for all the heat-trapping gases they pump into the atmosphere.
Even under conservative projections, scientists predict several degrees of warming this century, and possibly much more, which could shift precipitation patterns, disrupt agriculture and wildlife and eventually melt ice sheets, raising the level of the oceans and submerging low-lying coasts.
Delegates from outside the US expressed growing frustration with the administration of US President George W. Bush's environmental policy, saying that without clear signals from the world's largest source of air pollution, other countries would hesitate to move ahead.
The US is one of the few countries that has not ratified the Kyoto Protocol.
But Paula Dobriansky, the top US official at the conference, stood firm, saying that the best way to battle global warming was a mix of voluntary partnerships between developing and wealthy countries that foster economic growth while limiting pollution.
"The most effective strategies on climate change are those that are integrated with economic growth, with energy security, and with reducing air pollution," said Dobriansky, undersecretary of state for global affairs and democracy.
Jennifer Morgan, who directs energy and climate programs for E3G, a London-based environmental group, said that a letter sent to Bush from three influential Democratic senators on Wednesday -- and widely distributed in the conference halls -- provided at least a hint that a shift might be possible in Washington.
The letter, from Barbara Boxer of California, Jeff Bingaman of New Mexico and Joseph Lieberman of Connecticut, said Democrats would push to pass binding restrictions on greenhouse gases, starting in January when they take control of Congress.
"If we are to leave our children a world that resembles the earth we inherited, we must act now," they wrote.
"The senators' letter was very influential and welcome here," Morgan said.
Another central theme at the conference, reflecting its African venue, was the importance of boosting aid to the world's poorest countries to help them adapt to climate changes.
Many African communities are already suffering the effects of a shifting climate, from increased droughts to more desertification to spreading malaria, one of the continent's biggest killers.
The irony is that the countries most vulnerable to climate change are the least responsible for it, because they have little industry and produce a relatively small amount of pollution.
Though delegates began to discuss the ins and outs of an adaptation fund to aid developing nations, key decisions for the fund were postponed until next year.