CO2 levels rising faster as oceans trap less of greenhouse gas
Just days after the Nobel Prize was awarded for work that documents global warming, an alarming new study finds that carbon dioxide in the atmosphere is increasing faster than expected.
Carbon dioxide emissions were 35 per cent higher in 2006 than in 1990, a much faster growth rate than anticipated, researchers led by Josep G. Canadell, of Australia's Commonwealth Scientific and Industrial Research Organization, report in Tuesday's edition of Proceedings of the National Academy of Sciences.
Increased industrial use of fossil fuels coupled with a decline in the gas absorbed by the oceans and land were listed as causes of the increase.
"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 thegas out of the air, said Canadell, director of the Global Carbon Project at the research organization.
The changes "characterize a carbon cycle that is generating stronger-than-expected and sooner-than-expected climate forcing," the researchers report.
Kevin Trenberth of the climate analysis section of the National Center for Atmospheric Research in Boulder, Colo. said the "paper raises some very important issues that the public should be aware of: Namely that concentrations of CO2 are increasing at much higher rates than previously expected and this is in spite of the Kyoto Protocol that is designed to hold them down in Western countries."
Oceans absorbing less CO2
Alan Robock, associate director of the Center for Environmental Prediction at Rutgers University, added: "What is really shocking is the reduction of the oceanic CO2 sink," meaning the ability of the ocean to absorb carbon dioxide, removing it from the atmosphere.
The researchers blamed that reduction on changes in wind circulation, but Robock said he also thinks rising ocean temperatures reduce the ability to take in the gas.
"Think that a warm Coke has less fizz than a cold Coke," he said.
Neither Robock nor Trenberth was part of Canadell's research team.
Carbon dioxide is the leading greenhouse gas, so named because the accumulation of such gases in the atmosphere can help trap heat from the sun, causing potentially dangerous warming of the planet.
While most atmospheric scientists accept the idea, finding ways to reduce greenhouse gas emissions has been a political problem because of potential economic effects. Earlier this month, the Nobel Peace Prize was awarded to the United Nations Intergovernmental Panel on Climate Change and former U.S. vice-president Al Gore for their work in calling attention to global warming.
Change happening faster than predicted
"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," Robock commented. "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."
According to the new study, carbon released from burning fossil fuel and making cement rose from 7.0 billion metric tonnes per year in 2000 to 8.4 billion metric tonnes in 2006. A metric tonne is 1,000 kilograms.
The growth rate increased from 1.3 per cent per year in 1990-99 to 3.3 per cent per year in 2000-06, the researchers added.
Trenberth noted that carbon dioxide is not the whole story; methane emissions have declined, so total greenhouse gases are not increasing as much as carbon dioxide alone. Also, he added, other pollution plays a role by cooling.
There are changes from year to year in the fraction of the atmosphere made up of carbon dioxide and the question is whether this increase is transient or will be sustained, he said.
"The theory suggests increases in [the atmospheric fraction], as is claimed here, but the evidence is not strong," Trenberth said.
The paper looks at a rather short time to measure a trend, Robock added, "but the results they get certainly look reasonable, and much of the paper is looking at much longer trends."
The research was supported by Australian, European and other international agencies.