* Growing CO2 emissions could bust carbon budget by a third
* WWF report says world on track for dangerous warming
* U.N. talks struggling with "inadequate" CO2 cut pledges
By Chris Buckley
TIANJIN, China, Oct 6 (Reuters) - Greenhouse gas emissions worldwide risk overshooting by a third the threshold beyond which dangerous global warming looms, the environment group WWF said on Wednesday, urging climate talks in China to tackle the gap.
Negotiators from 177 governments are meeting this week in the north Chinese city of Tianjin trying to agree on the shape of the successor to the current phase of the Kyoto Protocol, the key U.N. treaty on fighting global warming, which expires in 2012.
Climate talks so far this year have focused on trust-building funding goals, with little talk about countries&${esc.hash}39; targets to reduce the greenhouse gases, especially carbon dioxide from fossil fuels and other sources, heating up the atmosphere.
The report from WWF said the world is precariously close to eating up its "carbon budget" -- the limit of carbon dioxide and other greenhouse gas emissions that would hold atmospheric concentrations below levels likely to trigger dangerous climate change, says the report.
"If we imagine the global carbon budget as a giant cake, the world has already gobbled up most of it," says the report.
"The climate talks in Tianjin need to see at least some indications of this trend changing," said Gordon Shepherd, the leader of the WWF Global Climate Initiative, in a press release accompanying the report, which was emailed to reporters.
Carbon dioxide is a crucial part of the atmosphere and is absorbed and released by plants, oceans and soils in a natural cycle.
But mankind&${esc.hash}39;s activities from burning fossil fuels to deforestation are disrupting this cycle, leading to more CO2 in the atmosphere than can be absorbed by nature. This accumulation is on course to overspend a limited carbon budget.
BALANCING THE BUDGET
How to share out the shrinking carbon budget will be a contentious part of climate change diplomacy for a long time.
Nations need to contain global greenhouse gas emissions to the equivalent of 40 billion tonnes (gigatonnes) of carbon dioxide a year by 2020 to contain future temperature rises at below 1.5 degrees Celsius from pre-industrial levels, said WWF.
"But the world is on track to emissions levels of 47.9 to 53.6 gigatonnes, based on promised reductions in major economies -- which on past experience may well not be achieved," it said.
Fraught climate negotiations last year failed to agree on a binding treaty and climaxed in a bitter meeting in Copenhagen, which produced a non-binding accord that later recorded the emissions pledges of participant countries.
Officials in Tianjin hope to foster agreement on climate funds for developing countries, protecting carbon-absorbing forests and transfers of green technology. These would be stepping stones for a high-level meeting in Cancun, Mexico, late this year.
That meeting, they hope, will build to a binding agreement late next year.
Some developed nations want a new treaty that binds all the big greenhouse gas polluters to emissions reductions. Kyoto only commits rich nations to meet emissions targets.
The U.N. climate change chief, Christiana Figueres, said on Monday the climate talks should now focus on securing formal pledges of the emissions cuts vows already made, "fully realising it is a first, necessary but insufficient step". [ID:nTOE69306P] (Editing by Chris Buckley)
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