In March, Russian ecologists said the mooted conference could be the occasion for Russia to announce a decision to ratify the Kyoto Protocol on greenhouse gases.

However "the conference will be purely scientific, and no political decision will be taken," Yury Izrael, head of the Academy of Sciences' Climate and Ecology Institute, told reporters.

Nearly 1,200 scientists, businessmen, government officials and representatives of non-government organisations from 43 countries are expected to attend the conference.

Britain, China, France, Germany, Italy, Japan and the United States are expected to send delegations.

Izrael said Russia's long-awaited ratification of the protocol setting a 2008-2012 deadline for industrialised signatories reduce their greenhouse gas emissions to below 1990 levels "has not yet been definitively decided."

A working group headed by Deputy Prime Minister Viktor Khristenko is still discussing the issue, "but there are still difficulties, particularly economic," Izrael said.

Russia is a major beneficiary of the Kyoto Protocol, the closure of many of its Soviet-era heavy industries, with their high pollution rates, since 1991 having granted it a wide margin on its quota and enabling it to sell billions of tonnes on the future emission rights market.

"If today we sell our quotas, then in 10 or 15 years, when the level of our carbon dioxide emissions rises, we'll be obliged to pay 10 times as much," Izrael noted.

The United States is refusing to sign the protocol, and Russia's ratification is essential for it to take effect.

Carbon-based greenhouse gases hang in the atmosphere like an invisible shroud, trapping solar heat rather than let it radiate safely out into space.

Scientists say that so many billions of tonnes of these gases have been spewed out, through burning oil, gas and coal, that Earth's climate system faces possibly catastrophic change in the coming decades.

Kyoto's framework was sketched in 1997, but it took four years to agree its highly complex rulebook.

SPACE.WIRE