* Industrialised nations can deepen CO2 cuts under treaty
* But risks they will promise more than they deliver
* Protecting forests, offsets could add to cuts
By Gerard Wynn and Alister Doyle
LONDON/OSLO, Aug 27 (Reuters) - Industrialised nations can deepen planned cuts in greenhouse gas emissions to shore up a U.N. climate treaty due in December but analysts say there are risks they will promise more than they deliver.
Measures such as paying to protect tropical forests -- which soak up carbon as they grow -- or wider use of carbon trading could help recession-hit rich nations add to pledged 2020 cuts which now total just 10 to 14 percent below 1990 levels.
That range is far short of the 25 to 40 percent outlined by the U.N. climate panel to avoid the worst of droughts, storms, heatwaves and rising seas. And developing nations such as China and India say the rich should cut by at least 40 percent.
"If we got closer to 20 or 25 percent...including forests and offsets then I think that would be pretty good," said Mark Kenber, policy director at The Climate Group in London. A new U.N. deal is due to be agreed in Copenhagen on Dec. 18.
To close the gap between 14 percent and 25 percent, developed nations as a group would have to offer extra annual reductions of 2.0 billion tonnes of carbon dioxide -- equivalent to the combined emissions of Japan and Canada [ID:nLR660640].
And there are risks some cuts may be hard to quantify -- for example offers of funds to boost low-carbon technologies.
"I'm certain that there will be a number of accounting exercises that may raise the numbers from today's level," said Knut Alfsen, head of research at the Center for International Climate and Environmental Research in Oslo (CICERO).
Countries with opportunities for deeper cuts included the Ukraine, Belarus, Russia, the United States and Canada, he said.
"Everybody's got a great reason not to put something on the table. As of today we're not heading to an ambitious outcome," said Nick Mabey, head of the E3G think tank in London.
Yvo de Boer, head of the U.N. Climate Change Secretariat, said there were legitimate ways of adding to planned cuts.
"Are we going to see broader issues of forestry addressed? What gases will be included? It's unclear at the moment to what extent flexibility mechanisms, offsets will apply on top of domestic action," he said.
Offsets let polluters invest, for instance, in a wind farm, a forest or a solar panel to counter emissions from burning fossil fuels. Flexibility mechanisms include carbon trading or investments in developing nations.
"People are looking at politicians to deliver real reductions, not smoke and mirrors," he added.
Analysts say tougher action is possible, for instance to tighten U.S. President Barack Obama's 2020 goal of returning emissions to 1990 levels, a 14 percent cut from 2007. It is widely criticised by developing nations as inadequate.
The World Resources Institute (WRI) think-tank in Washington, for instance, said U.S. emissions could fall by 17 percent below 1990 levels by 2020 with "complementary" policies.
For example, the United States could offer in Copenhagen to turn international measures in its draft climate law, such as funds to protect rainforests, into binding commitments and count those as emissions cuts within its 2020 target.
"There is always room for negotiation," said Kelly Levin of the WRI, of possibilities for all industrialised nations to step up regulatory standards, taxes and fees, cap and trade, clean energies, offsets or even crack down on illegal logging.
"For example, a country like Japan which has a target that is to be met solely by domestic actions has stated that it's open to discussing how its target could increase with the use of international reduction mechanisms," she said.
Recession is a big barrier to domestic action by the rich.
"It is unlikely that the developed world will be able to commit to bigger cuts than the ones that have been already promised," said Pep Canadell, head of the global carbon project at Australia's Commonwealth, Scientific and Industrial Research Organization.
"The reasons are various but mostly because 2020 is just 10 years away and there is so much industrial transformation you can do in 10 years, let alone during times of recovery from the worst economic crisis of the last 80 years," he said.
Under the U.N. deal, developing nations such as China, India and Brazil are expected to curb the rise of their emissions, without making absolute cuts by 2020. Beijing says it would like to cap emissions soon but priority must go to ending poverty.
One big chance to shore up the treaty is to give credits for slowing deforestation in developing nations -- deforestation now accounts for 20 percent of world greenhouse gas emissions.
"Here is a very, very large chunk of the world's emissions from deforestation which you can stop relatively quickly," said Kenber. Trees release carbon when they burn or rot.
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