Carbon dioxide emissions from fossil fuels - the principal driver of climate change - have accelerated globally at a far greater rate than expected over recent years, according to a paper published this week in the Proceedings of the National Academy of Sciences.
The paper explains that the average growth rate of carbon dioxide emissions increased from 1.1 per cent a year in the 1990s to a three per cent increase per year in the 2000s.
Lead author of the paper, Dr Mike Raupach from CSIRO Marine and Atmospheric Research and the Global Carbon Project, says that nearly eight billion tonnes of carbon were emitted globally into the atmosphere as carbon dioxide in 2005, compared with just six billion tonnes in 1995.
"A major driver of the accelerating growth rate in emissions is that, globally, we're burning more carbon per dollar of wealth created," Dr Raupach says. In the last few years, the global usage of fossil fuels has actually become less efficient. This adds to pressures from increasing population and wealth."
"As countries undergo industrial development, they move through a period of intensive, and often inefficient, use of fossil fuel. Efficiencies improve along this development trajectory, but eventually tend to level off. Industrialised countries such as Australia and the US are at the levelling-off stage, while developing countries such as China are at the intensive-development stage. Both factors are decreasing the global efficiency of fossil fuel use."
He says that China's emissions per person are still below the global average. "On average, each person in Australia and the US now emits more than five tonnes of carbon per year, while in China the figure is only one tonne per year. Since the start of the industrial revolution, the US and Europe account for more than 50 per cent of the total, accumulated global emissions over two centuries, while China accounts for less than eight per cent. The 50 least developed countries have together contributed less than 0.5 per cent of global cumulative emissions over 200 years."
Dr Raupach says that Australia, with 0.32 per cent of the global population, contributes 1.43 per cent of the world's carbon emissions.
He says recent efforts globally to reduce emissions have had little impact on emissions growth. "Recent emissions seem to be near the high end of the fossil fuel use scenarios used by the Intergovernmental Panel on Climate Change (IPCC). Our results add to previous findings that carbon dioxide concentrations, global temperatures and sea level rise are all near the high end of IPCC projections."
Dr Raupach led an international team of carbon-cycle experts, emissions experts and economists, brought together by the Global Carbon Project, to quantify global carbon emissions and their drivers.
"In addition to reinforcing the urgency of the need to reduce emissions, an important outcome of this work is to show that carbon emissions have history. We have to take both present and past emissions trajectories into account in negotiating global emissions reductions. To be effective, emissions reductions have to be both workable and equitable," he says.