A new deal to fight climate change from 2013 should be less rigid than the UN's Kyoto Protocol but it may still be hard to attract outsiders like China and the United States, the biggest greenhouse gas emitters, experts say.
About 80 world leaders will meet at the United Nations on Monday and major emitters will meet in Washington on September 27-28 to discuss a successor to Kyoto, hailed by backers as a key step to slow warming but reviled by opponents as a straitjacket.
"The Kyoto world is a world of countries with binding targets, and other countries without. Perhaps we need more flexibility, more options," Yvo de Boer, head of the UN Climate Change Secretariat, told Reuters. Kyoto obliges 36 industrial nations to cut emissions of greenhouse gases, mainly from burning fossil fuels, by at least 5 percent below 1990 levels by 2008-12. The United Nations wants details of a new global accord worked out by the end of 2009.
Ideas include paying developing nations credits to slow deforestation, sharing clean technology such as windmills and solar power and boosting funds to help them adapt to impacts such as floods, droughts, heatwaves and rising sea levels.
De Boer said that a cornerstone, as in Kyoto, should be legally binding cuts for industrialised nations to offset warming and to help drive markets for trading carbon dioxide, the main greenhouse gas.
Such a policy has so far been rejected by US President George W. Bush, who says the Kyoto model is unfair because it does not set 2012 targets for developing nations and would cost US jobs. Bush has preferred voluntary goals.
"The politics, economics and complexity of the climate issue are ... probably the most difficult negotiation that the United Nations would see," said Timothy Wirth, President of the UN foundation and a US climate negotiator in the 1990s.
A key problem is how to share out the burden of a global pact between countries such as Bhutan, where trees soak up more carbon than its people emit, and rich nations such as the United States where each person emits more than 20 tonnes a year.
Rich nations have emitted most greenhouse gases since the Industrial Revolution but the poor are catching up. China, drawing level with the United Sates as the top emitter, is opening a coal-fired power plant almost twice a week.
The Club of Madrid, a think-tank grouping former world leaders, proposed last week that developed nations should cut emissions by 30 percent below 1990 levels by 2020, and rapidly industrialising nations should cut the amount of energy they use per dollar of economic output by 30 percent by 2020.
But there are many problems. Kyoto member Croatia, for instance, is poorer per capita than several countries with no targets such as South Korea, Argentina, Kuwait and Singapore. Kyoto's successor could be widened in other ways. "Perhaps we will be wanting to bring more sources of emissions into a future agreement," de Boer said, noting that international aviation and shipping were outside Kyoto.
There will also have to be safeguards to prevent industries such as steel or aluminium from moving to nations with easier targets. "If you impose very severe restrictions on them in countries which have targets it's very easy to get leakage to other countries that are not imposing targets," de Boer said.
Others say the Kyoto model should be abandoned. Denmark's Bjorn Lomborg, author of "The Skeptical Environmentalist", said that Kyoto would cost $180 billion a year for little effect.
The world should instead spend 0.05 percent of gross domestic product on developing non-carbon emitting energy sources, raising spending tenfold to $25 billion a year, he said. "It will be much more politically doable, will have enormous potential spin-offs and ultimately do much more good than both Kyoto I and Kyoto II," he said.