Finger-pointing, and "China bashing" in particular, is a favourite game when it comes to assigning responsibility for climate change.
But things are not always as straightforward as they seem. Developed countries import many of the products that contribute to China's greenhouse gas emissions.
Economists now say that one-third of China's carbon dioxide emissions are pumped into the atmosphere in order to manufacture exported goods – many of them "advanced" electronics goods destined for developed countries.
"Export goods emissions" account for 1.7 billion tonnes of China's carbon dioxide. That represents 6% of total global emissions – the equivalent of Germany, France and the UK's combined emissions.
Discussing the scale of China's emissions has been a hot topic since it was forecast that they could surpass US emissions as the world's leader in 2007. Some say that has now happened.
A large share of these emissions – up to 25% – has been blamed on China's ever-growing export market, but this has not been quantified until now.
Now Christopher Weber of Carnegie Mellon University in Pittsburgh, Pennsylvania, and colleagues have shown that the figure is larger still.
Weber's team used a standard model of the Chinese economy, produced by the Chinese government. This model, which operates on the same principle as others produced by every national government, reflects how money has flowed in and out of different sectors of the economy since the 1980s.
They combined this with nationally-produced emissions data, which shows how much emissions are produced by which sectors.
Matching the model to the dataset allowed the team to calculate that, in 2005, export sectors generated 1.7 billion tonnes of carbon dioxide – 33% of China's emissions. Data is not yet available for more recent years.
Weber says that, in 1987, exports accounted for just 230 million tonnes, 12% of China's total emissions.
Interestingly, even as Chinese export emissions have risen, so have the emissions the nation avoids by importing primary products such as minerals and basic metals. This switch reflects China's switch from a primary to a secondary producer. Increasingly, the products it is exporting are "advanced" products.
For instance, in 2005 electronics accounted for 22% of the export emissions, up from 13% in 1987.
China is very aware that much of its carbon footprint is export emissions, and has used this as an argument against adopting Kyoto-Protocol-like emissions caps. Other major emitters, including the US and Europe, it says, demand and consume the products so they should bear the burden of responsibility for the emissions.
International policy at the moment tends to penalise the country which produces goods rather than the one that consumes them.
"In some measure, it makes sense if people buy goods and become liable for the emissions generated when the goods are produced," says Benito Müller of the Oxford Institute for Energy Studies, UK. "They will certainly be more choosy about what they buy."
How to fairly apportion the liability for China's exported emissions "is the million-dollar question", says Weber.
"It's just like narcotics," says Müller. "Who is responsible, the drug baron or the junkies?"