* China study questions 2 degrees limit to global warming
* Says China can contain greenhouse gas emissions growth
* Says effort requires major new spending
* Experts say low-carbon path difficult and uncertain
(Recasts to focus on global warming temperature target)
By Chris Buckley
BEIJING, Sept 16 (Reuters) - An international goal to limit global warming to no more than 2 degrees Celsius appears unreachable even if China embarks on a vast effort to tame its growing greenhouse gas emissions, a Beijing think-tank has said.
The report cast doubt on the prospects for the world to stay within a commonly accepted threshold of dangerous climate change, to avoid worse droughts, floods and rising seas, two months after world leaders including China acknowledged the limit.
China's Energy Research Institute also underlined in its new report concerns among developing countries that a goal to halve global greenhouses gases by 2050, resisted by China and other emerging economies, may cramp their growth.
Even if China embraces rigorous low-carbon policies, the chances were slim that the world could achieve that goal, said the report released in Beijing on Wednesday.
"According to our calculations, these goals don't in fact leave enough space for developing countries," Bai Quan, one of the researchers who wrote the report, told a meeting marking its release.
"You can't hang achieving this 2 degrees goal on China," said Dai Yinde, deputy director of the Institute, adding that it was up to the rich nations to lead with big emissions cuts of 90 percent or more by 2050, compared to 1990 levels.
Without these deep cuts, greenhouse gas concentrations are likely to rise this century so the average global temperature rises by around 2.8-3.2 degrees Celsius above the pre-industrial average, says the study.
China is the world's biggest emitter of carbon dioxide, the main greenhouse gas from burning fossil fuels, and with enough money and tough low-carbon policies, those emissions could peak around 2030-35 and then by 2050 fall to the same level as 2005, the report found.
IMMERSED
Governments are immersed in negotiations seeking a new global treaty on fighting climate change by the end of 2009, and China with its bulging greenhouse gas output is a key player.
Chinese President Hu Jintao will present his government's general plans for tackling global warming at a United Nations meeting on climate change next week, the country's senior official on the issue said on Tuesday.
Wednesday's new report, "China's Low Carbon Development Pathways by 2050," examines policy options that could help China avoid emissions levels that could tower over those of the United States, long the world's biggest emitter.
The report does not amount to government policy. But coming from a prominent institute that advises officials, it illuminates some of China's key concerns less than three months before the climate pact negotiations culminate in Copenhagen.
"This kind of research confirms the impression that China's position (on climate change) is shifting and there's a very healthy debate," said Jim Watson, an expert on energy policy at the University of Sussex who studies China's emissions.
"That's heartening. But the numbers are still really daunting," Watson said in a telephone interview before its release. "They just show the sheer scale of the challenge."
BIG COSTS AND UNCERTAINTIES
The new report builds on another recent report from the Institute that gave slightly different greenhouse gas growth scenarios.
If China adopts "low-carbon development", emissions from burning fossil fuels could peak at 2.4 billion tonnes of carbon a year by 2035 and then remain close to that level for at least 15 years. Under current trends they could reach 3.3 billion tonnes of carbon a year by 2050, compared with global carbon emissions of about 8.5 billion tonnes now.
Under an "enhanced low carbon scenario" of more stringent steps, China's emissions could peak at 2.2 billion tonnes around 2035 and fall to 1.4 billion tonnes in 2050. But achieving major reductions in emissions will carry a big cost, the report said.
A low-carbon growth path would cost about 1.7 trillion yuan ($249 billion) extra a year by 2030 for energy-efficient industry, transport and buildings, and similar levels in 2050, a graph and data in the study indicated.
China's current growth stimulus package amounts to 4 trillion yuan, including bank loans, spent across two years.
Bai, the researcher, said China could follow the low-carbon path described in the report only with intense difficulty, and the enhanced low-carbon path was virtually out of reach.
($1=6.83 yuan)
(Editing by Gerard Wynn)