Unexpected Growth In Atmospheric Carbon Dioxide

Lead author and Executive Director of the Global Carbon Project, CSIRO’s Dr Pep Canadell, says the acceleration is due to three factors: global economic growth; the world’s economy becoming more carbon intense (that is, since 2000 more carbon is being emitted to produce each dollar of global wealth); and a deterioration in the land and oceans’ ability to absorb carbon from the atmosphere at the required rate.

“What we are seeing is a decrease in the planet’s ability to absorb carbon emissions due to human activity,” Dr Canadell says.

“Fifty years ago, for every tonne of CO₂ emitted, 600kg were removed by land and ocean sinks. However, in 2006, only 550kg were removed per tonne and that amount is falling.”

The study found that inefficiency in the use of fossil fuels increased levels of CO₂ by 17 percent, while the other 18 percent came from the decline in the efficiency of natural land and ocean sinks which soak up CO₂ from the atmosphere.

The research by the Global Carbon Project, the University of East Anglia (UEA) and the British Antarctic Survey (BAS) shows that improvements in the carbon intensity of the global economy have stalled since 2000 after improving for 30 years, leading to the unexpected growth of atmospheric CO₂.

The study also states that global CO₂ emissions were up to 9.9 billion tons of carbon in 2006, 35 percent above emissions in 1990 (used as a reference year in the Kyoto Protocol).

Author Dr Corinne Le Quéré of the University of East Anglia and British Antarctic Survey says, "The decline in global sink efficiency suggests that stabilisation of atmospheric CO₂ is even more difficult to achieve than previously thought. We found that nearly half of the decline in the efficiency of the ocean CO₂ sink is due to the intensification of the winds in the Southern Ocean."

The study's lead author, Dr Pep Canadell, executive director of the Global Carbon Project, said: "In addition to the growth of global population and wealth, we now know that significant contributions to the growth of atmospheric CO₂ arise from the slow-down of natural sinks and the halt to improvements in the carbon intensity of wealth production."

Reference: Contributions to accelerating atmospheric CO₂ growth from economic activity, carbon intensity, and efficiency of natural sinks by Josep Canadell, Corinne Le Quéré, Michael Raupach, Christopher Field, Erik Buitenhuis, Philippe Ciais, Thomas Conway, Nathan Gillett, RA Houghton and Gregg Marland is published on Monday October 22 in the Proceedings of the National Academy of Sciences of the United States of America.

The authors analysed atmospheric CO₂ observations and CO₂ emissions data since 1959 and compared observed and projected trends.

The Southern Ocean winds have increased in response to greenhouse gases and ozone depletion. The increase in winds has led to a release of natural CO₂ stored in the deep ocean, which is preventing further absorption of the greenhouse gas.