The case for firms to address the carbon impact of their international supply chains has strengthened further following the publication of the third study in the last six weeks highlighting the extent to which the growth in China's carbon emissions are largely a result of exports to the West.

The study from researchers at Carnegie Mellon University in the US appeared in the journal Energy Policy late last month and estimated that the boom in Chinese exports over the past decade has made a significant contribution to its rising carbon emissions.

"We found that in 2005, fully one-third of China's greenhouse gas emissions were due to production of exports," Christopher L. Weber, a research professor in the university's Department of Civil and Environmental Engineering. "This proportion has risen quickly, from 12 per cent in 1987 and only 21 per cent in 2002."

The report noted that while China's status as the world's largest polluter meant that the onus was now on the Chinese government to increase investment in energy efficiency and renewable energy, western businesses and governments also had to accept they were indirectly responsible for a large chunk of China's emissions and should help fund mitigation measures.

"It is clear that urgent improvements are needed, especially in China's electricity sector," Weber said. "Installing more renewable power and overcoming the financial and technological hurdles involved with new technologies such as carbon sequestration should be the first priority of both China and its export partners."

The study follows two similar research papers released last month, both of which highlighted the extent to which the UK has effectively exported much of its carbon footprint to trading partners such as China.

A study carried out by the Stockholm Environment Institute for the WWF calculated that when greenhouse gas emissions from aviation, shipping and imported goods and services are included the UK's full carbon footprint is 49 per cent higher than official figures for domestic emissions.

Meanwhile, another SEI study commissioned by the government showed that while UK domestic emissions fell five per cent between 1992 and 2004, the shift in manufacturing capacity to countries such as China and India meant that UK-related CO2 emissions including those from international transport and net imports rose 18 per cent.