A new study has shown that Australians have overtaken Americans as the world's highest per capita carbon dioxide polluters.

The global pollution report has been compiled by a British company, Maplecroft.  Using U.S. Energy Department data it calculated that Australia's per capita output of carbon dioxide at 18.66 metric tons a year, four percent higher than the United States.

In a list of 185 countries, Canada, the Netherlands and Saudi Arabia rounded out the top five.

China remains the world's biggest overall greenhouse gas polluter, followed by the United States.

Australia's position as the worst per capita emitter of carbon dioxide, which many scientists blame for global warming, is a result of its heavy reliance on cheap supplies of coal.  About 80 percent of the country's electricity is generated by coal-fired power stations.

Canberra has committed to cutting its greenhouse gas pollution by up to 25 percent by 2020 compared to 2000 levels.

Professor Barry Brook from Adelaide University says a global plan of action to cut emissions is more important than the performance of individual countries.

"Australia has about five times the per capita emissions of China for instance but China produces over 20 times the carbon emissions of Australia because China has such a huge population," he said.  "So you can play around with these numbers all you want but ultimately what matters is the total global carbon budget and unless humanity as a whole can find solutions to that problem then all of that petty bickering amongst nations about who's more or less responsible isn't really going to be very helpful."

The British pollution report has been released ahead of a major United Nations summit in Copenhagen in December aiming to agree to a new climate change treaty to replace the Kyoto Protocol.

The Australian government hopes to have a sweeping carbon emissions trading system in place before the summit in Denmark.  Its plans, however, suffered a parliamentary defeat last month, leaving the program in doubt.

Scientists have warned that Australia - a vast, dry island that is home to 21 million people - is particularly susceptible to the effects of global warming and could suffer more severe bushfires, droughts and storms if temperatures continue to rise.

Parts of Australia have experienced their warmest winters on record, which climatologists have blamed on both the effects of climate change and natural variability.