Despite China's pledges to improve energy efficiency, its carbon emissions could double by 2020 as compared with 2005 levels, surpassing limits seen as key to fighting global warming, experts say.
As officials in Copenhagen discuss how nations can share the global burden of reducing greenhouse gas emissions, experts are crunching the numbers to determine the future level of emissions by China, the world's top polluter.
Even if China keeps its promise to reduce carbon emissions per unit of gross domestic product (GDP) by 40 to 45 percent by 2020, and if its economy grows by just eight percent, its gas output could still double, they say.
"With eight percent growth, emissions will increase by 74 percent," said Emmanuel Guerin, a climate analyst at France's Institute for Sustainable Development and International Relations (IDDRI).
"China, having emitted 7.2 gigatonnes of carbon dioxide equivalent in 2005, will spew out 12.6 gigatonnes in 2020," he told AFP by telephone from the Danish capital.
"That is one gigatonne too many, according to the scenario laid out by (leading climate change expert) Nicholas Stern, who put the range at 7.9-11.6 gigatonnes."
The estimated total emissions by China is also equal to nearly 29 percent of the worldwide goal.
"With a view to limiting global warming to two degrees, the world should not emit more than 44 gigatonnes of carbon dioxide equivalent in 2020," he said.
Another study by a panel of European experts says China's total emissions could be even higher.
"Chinese carbon emissions will double by 2020," a member of that panel said on condition of anonymity, confirming a similar estimate given by Australian academic Frank Jotzo.
Taking into account China's stated goal to reduce carbon intensity, "emissions will 'only' double," Jotzo, deputy director of the Climate Change Institute at Australian National University, said after Beijing's announcement.
The European expert, calculating from a different 2005 base figure, said if the Chinese economy grew by eight percent annually, total greenhouse gas emissions could nearly double in 2020, reaching a high of 10.7 gigatonnes.
According to his calculations, the Chinese increase in gas emissions would be three or four times higher than the combined cuts promised by the United States and the European Union.
At that rate, China -- which says it lags far behind the developed world in terms of tonnes of emissions per capita -- would in fact bypass France on those terms in 2012 or 2013, and the entire European Union between 2018 and 2020.
"This hypothesis is based on European emissions reductions and Chinese emissions increases," said Wang Ke, a professor in the school of environment and natural resources studies at People's University in Beijing.
"But the question is: under what terms will the EU manage its reductions?"
The European Commission, which says it has not calculated China's future emissions levels, hailed Beijing's stated goal to slow emissions growth, but said there would be more work to do.
"Since the reduction goal is linked to GDP, with expected high economic growth in the next 10 years, Chinese emissions will most likely continue to grow very rapidly," said the commission's environment spokeswoman, Barbara Helfferich.
"Higher GDP growth rates would require higher CO2 intensity improvements in order to meet an emissions trajectory that limits climate change to two degrees Celsius," she said.
Beyond its carbon intensity pledge, China has made other commitments to slow emissions, such as through reforestation.