The world has seen a rapid rise in carbon dioxide (CO2) emissions from fossil fuels over recent years, U.S. scientists said.
CO2 emissions have accelerated globally at a far greater rate than expected, 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 percent a year in the 1990s to a 3-percent increase per year in the 2000s.
Nearly 8 billion tons of carbon were emitted globally into the atmosphere as carbon dioxide in 2005, compared with just 6 billion tons in 1995, says Lead author of the paper, Dr Mike Raupach from CSIRO Marine and Atmospheric Research and the Global Carbon Project.
This indicates that recent efforts globally to reduce emissions have had little impact on emissions growth, according to Raupach.
"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," Raupach says.
"As countries undergo industrial development, they move through a period of intensive, and often inefficient, use of fossil fuel," he says.
Efficiencies improve along this development trajectory, but eventually tend to level off. Industrialized countries such as Australia and the U.S. are at the leveling-off stage, while developing countries are at the intensive-development stage, according to Raupach.
"Both factors are decreasing the global efficiency of fossil fuel use," he says.
He says that China's emissions per person are still below the global average. "On average, each person in Australia and the U.S. now emits more than five tons of carbon per year, while in China the figure is only one ton per year."
Since the start of the industrial revolution, the United States and Europe account for more than 50 percent of the total, accumulated global emissions over two centuries, while China accounts for less than eight percent, according to Raupach.
"The 50 least developed countries have together contributed less than 0.5 percent of global cumulative emissions over 200 years."