 China's greenhouse gas pollution could double or more in two decades says a new Chinese state think-tank study that casts stark light on the industrial giant's role in stoking global warming. Beijing has not released recent official data on greenhouse gas from the nation's fast-growing use of coal, oil and gas. Researchers abroad estimate that China's carbon dioxide emissions now easily outstrip that of the United States, long the biggest emitter. But in a break with official reticence, researchers from the Chinese Academy of Sciences and other major state-run institutes have concluded that, without dramatic counter-steps, their nation's emissions will tower over all others' much sooner than an earlier government forecast. The projected leap in emissions underscores the pressures that China will face in looming climate change negotiations, and the immense challenges it would face in meeting any commitments. By 2020, China's burning of fossil fuels could emit carbon dioxide equal in mass to 2.5 billion metric tonnes of pure carbon and up to 2.9 billion tonnes, depending on varying scenarios for development and technology. By 2030, those emissions may reach 3.1 billion tonnes and up to 4.0 billion tonnes. That compares with global carbon emissions of about 8.5 billion tonnes in 2007. Emissions are also often estimated in tonnes of Co2, which weighs 3.67 times as much as carbon alone. The report does not give its own estimate of China's current Co2 emissions, but cites data from a U.S. Department of Energy institute that put them at 1.4 billion tonnes of carbon in 2004. The U.S. Oak Ridge National Laboratory estimated that the United States emitted about 1.6 billion tonnes of carbon in 2007, compared to China's 1.8 billion tonnes. The "China Energy Report" for 2008 warns of drastic risks from inaction in the face of this projected growth, and yet also says economic development must not be hobbled. "No matter how historical responsibility is defined, our country's development path cannot repeat the unconstrained emissions of developed countries' energy use," states the Chinese-language report, which recently went on public sale without fanfare. "Therefore, we must soon prepare and plan ahead to implement emissions reduction concepts and measures in a long-term and stable energy development strategy." The main author, Wei Yiming, has participated in a U.N. scientific panel to assess global warming. He was not immediately available for comment on the findings and why they appeared now. BUILDS PRESSURE The study may add to contention over China's response to global warming at a time of accelerating international negotiations. Beijing will be at the heart of efforts to forge a treaty next year to succeed the first phase of the Kyoto Protocol, which expires at the end of 2012. The European Union this week said developing countries should accept a 15-30 percent cut in their greenhouse gas emissions from "business-as-usual" levels. But under the Protocol, a U.N.-led pact, poor nations do not assume targets to cap emissions. And Washington has refused to ratify Kyoto partly because it says the treaty is ineffective without Beijing's acceptance of such mandatory caps. Carbon dioxide and other greenhouse gases trap solar radiation, heating the atmosphere and threatening to stoke worsening drought, disrupted rainfall and more wild weather. But China points out that per capita emissions of its 1.3 billion people are much lower than rich countries' and says the developed countries bear overwhelming responsibility for the dangerous accumulation of greenhouse gases. The new study backs that argument. Beijing officials have also often said they will not sacrifice hard-won economic development to greenhouse gas caps. For China, "relative to reducing carbon dioxide emissions, economic development is even more important," the study says.