A pilot project to curb greenhouse gases until 2012, Kyoto applies only to developed nations causing about 40 percent of global emissions of heat-trapping gases.

It will be a pinprick in braking what experts say could be a catastrophic rise in temperatures.

"We must now redouble efforts to deliver the even deeper cuts in emissions needed," said Klaus Toepfer, head of the U.N. Environment Programme after the Russian vote.

"The big challenge will be to get involvement by the United States, big developing countries like China, India, Brazil and Indonesia," Paal Prestrud, head of the Centre for International Climate and Environmental Research, Oslo.

The chances of involving the United States, the world's top polluter, will improve if Democratic Senator John Kerry beats President George W. Bush in the November 2 election. Bush said Kyoto was too expensive and unfair for excluding developing nations.

Other rich nations agreed to go ahead anyway, reckoning that their factories, power plants and cars have been the main source of carbon dioxide, blamed for driving up temperatures by blanketing the planet.

Under Kyoto, developed countries will have to cut overall emissions of carbon dioxide by at least five percent below 1990 levels by 2008-12. Nations including China and India have ratified Kyoto but have no targets to meet by 2012.

BLUEPRINT

Still, Jennifer Morgan of the WWF conservation group said Kyoto laid down a blueprint.

"It will be much more difficult for (non-Kyoto) countries like the United States or Australia to bring in other less ambitious proposals ... With Kyoto you have a system of binding caps," she said.

And oil at $50 a barrel may help developing nations focus on cutting down on burning fossil fuels and switching to cleaner technology.

The United Nations projects that temperatures may rise by 1.4-5.8 Celsius by the year 2100. That may spur catastrophic changes that could raise sea levels, swamp low-lying states, bring desertification and floods that may trigger famines or spread diseases.

Even if fully implemented to 2012, Kyoto would only curb the projected rise in temperatures by 0.15 C, requiring far deeper cuts likely to cost trillions of dollars.

The United States alone accounts for about a fifth of world carbon dioxide emissions from human sources. China is number two and India and Brazil are also among the top 10.

Prestrud said the world needed to develop clean technology in a global effort equivalent to the U.S. Apollo project that put Neil Armstrong and Buzz Aldrin on the moon in 1969.

But critics say Kyoto is based on shoddy science and that trillions of dollars could be better spent on combating diseases like AIDS or malaria.