Earth's ability to deal with CO2 studied

BOULDER, Colo., Aug. 1 (UPI) -- Carbon dioxide emissions are still rising but so is the capacity of Earth's vegetation and oceans to soak up much of it, a U.S. study found.

Despite sharp increases in carbon dioxide emissions from human activities in recent decades that are warming the planet, the Earth has shown it can absorb about half of them, researchers at the University of Colorado at Boulder reported Wednesday.

The study examined CO2 emissions reports from the past 50 years showing rising levels of CO2 in Earth's atmosphere during that time and found that while CO2 emissions had quadrupled, natural carbon "sinks" that sequester the greenhouse gas doubled their uptake in the past 50 years, lessening the warming impacts on Earth's climate.

"What we are seeing is that the Earth continues to do the heavy lifting by taking up huge amounts of carbon dioxide, even while humans have done very little to reduce carbon emissions," post-doctoral researcher Ashley Ballantyne said.

"How long this will continue, we don't know."

Earth's natural carbon sinks cannot absorb atmospheric carbon indefinitely, researchers said.

"It's not a question of whether or not natural sinks will slow their uptake of carbon, but when," doctoral student Caroline Alden said.

"We're already seeing climate change happen despite the fact that only half of fossil fuel emissions stay in the atmosphere while the other half is drawn down by the land biosphere and oceans," she said. "If natural sinks saturate as models predict, the impact of human emissions on atmospheric CO2 will double."