Carbon dioxide levels in the atmosphere are increasing much faster and will be harder to control than scientists have predicted, a study has found.
An international team of researchers has found that, since 2000, the rate at which CO2 has been pumped into the atmosphere is 35 percent greater than most climate-change models have allowed for.
The conclusions have serious implications for forecasts of how much and how quickly the world's temperature will rise and mean that global warming will be harder and more expensive to control than feared.
The results also mean that international efforts to bring CO2 emissions under control will need to be more far-reaching.
Professor Nicholas Owens, of the British Antarctic Survey (BAS), said that the findings were so worrying that they made previous widely accepted forecasts of climate change seem unduly optimistic.
In February, the International Panel on Climate Change, the United Nations body devoted to assessing the likely extent and impact of global warming, judged that world temperatures would rise by up to 6.4 degrees Centigrade (11.5 degrees Fahrenheit) over the next century.
But the findings of the team of researchers, who include Corinne Le Quéré, of the BAS and the University of East Anglia, may force the IPCC to revise its predictions.
"There's quite a significant difference from what was forecast," she said. "It's rather scary and the IPCC scenarios are, therefore, rather too optimistic -- as if they weren't bleak enough already. The whole thing is likely to mean mitigation is rather more difficult than was thought."
[The research team was led by Josep G. Canadell of Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO).]
Rapid expansion of the Chinese and Indian economies was thought to be at least partly responsible for the increase in the rate that CO2 has been emitted into the atmosphere.
The study identifies inefficient use of fossil fuels as a prime cause of the rise in emissions, and the number of coal-fired power plants being built in India and China is identified as one of the key causes of that inefficiency.
Previous models for climate change had allowed for an expansion in the global economy, but also assumed that the trend towards more efficient burning of fossil fuels would continue.
Recent research has also noticed a reduction in the ability of the oceans and the land to absorb carbon.
["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 slowdown" of nature's ability to take the chemical out of the air, Canadell, director of the Global Carbon Project at CSIRO, told the Associated Press.]
The problem with the seas was identified this year in the Southern Ocean around Antarctica, where winds driven by climate change are bringing carbon-saturated waters to the surface, which are unable to absorb any more carbon.
["What is really shocking is the reduction of the oceanic CO2 sink," Alan Robock, associate director of the Center for Environmental Prediction at Rutgers University, told the AP, referring to the ability of the ocean to absorb carbon dioxide.
The researchers blamed wind circulation for the reduction, but Robock, who was not part of the study, said he also thinks rising ocean temperatures play a role.
"Think that a warm Coke has less fizz than a cold Coke," he said.]
Droughts, a further by-product of climate change, are suggested as a reason why land is absorbing less carbon.
The latest study has been published in the journal Proceedings of the National Academy of Sciences.
In 2006, global CO2 emissions were found to have risen to 9.9 billion metric tons, 35 percent above levels in 1990.
"The decline in global sink efficiency suggests that stabilization of atmospheric CO2 is even more difficult to achieve than previously thought," said Le Quéré. "We found that nearly half of the decline in the efficiency of the ocean CO2 sink is due to the intensification of the winds."
["It turns out that global-warming critics were right when they said that global climate models did not do a good job at predicting climate change," said Robock. "But what has been wrong recently is that the climate is changing even faster than the models said. In fact, Arctic sea ice is melting much faster than any models predicted, and sea level is rising much faster than IPCC previously predicted."]