Earth's minerals kept CO2 levels in balance prior to humans
April 28, 2008

CO2 emissions are presently 100 times the natural rate

The natural feedback system that has kept Earth's atmospheric carbon dioxide levels finely-balanced for millions of years has been overwhelmed by fossil fuel combustion, reports a new study published in Nature Geoscience.

Analyzing atmospheric CO2 levels for the past 610,000 years using data from gas bubbles trapped in Antarctic ice cores, Ken Caldeira of the Carnegie Institution's Department of Global Ecology and Richard Zeebe of the University of Hawaii modeled how carbon dioxide released into the atmosphere from natural sources is "ultimately recycled via carbon-bearing minerals back into the crust," according to a statement from the Carnegie Institution.

"The researchers found that over hundreds of thousands of years the equilibrium between carbon dioxide input and removal was never more than one to two percent out of balance, a strong indication of a natural feedback system," wrote Alan Cutler, a science writer for Carnegie. "This natural feedback acts as a thermostat which is critical for the long-term stability of climate. During Earth's history it has probably helped to prevent runaway greenhouse and icehouse conditions over time scales of millions to billions of years — a prerequisite for sustaining liquid water on Earth's surface."

"The system is finely in tune," Caldeira told Cutler. "That one or two percent imbalance works out to an average imbalance in natural carbon dioxide emissions that is thousands of times smaller than our current emissions from industry and the destruction of forests."

The researchers note that carbon dioxide is presently being added at about 100 times its historic rate of 0.1 billion tons of carbon each year, or approximately 10 billion tons. Most of these emissions result from human industrial activity and conversion of forests.

"The imbalance in the carbon cycle that we are creating with our emissions is huge compared to the kinds of imbalances seen over the time of the glacial ice core records," Caldeira said. "We are emitting CO2 far too fast to expect mother nature to mop up our mess anytime soon. Continued burning of coal, oil and gas will result in long-term changes to our climate and to ocean chemistry, lasting many thousands of years."

CITATION: (April 28, 2008).

Earth's minerals kept CO2 levels in balance prior to humans.