WASHINGTON: Carbon dioxide levels in the atmosphere have entered the danger zone and must be reduced if climate disasters are to be averted,
according to researchers.
US, British and French scientists, including two from Yale, said in a study that optimum CO2 level should be less than 350 parts per million (ppm) - a dramatic change from most studies that have pegged the danger level for CO2 at 450 ppm or higher.
Atmospheric CO2 is currently 385 ppm and is increasing by about two ppm every year from the burning of coal, oil, gas and forests.
"This work and other recent publications suggest that we have reached CO2 levels that compromise the stability of the polar ice sheets," said author Mark Pagani, Yale professor of geology and geophysics.
"How fast ice sheets and sea level will respond are still poorly understood, but given the potential size of the disaster, I think it's best not to learn this lesson firsthand," he said.
The statement is based on improved data on the earth's climate history and ongoing observations of change, especially in the polar regions, said an Yale University release.
The authors use evidence of how the earth responded to past changes of CO2 along with more recent patterns of climate changes to show that atmospheric CO2 has already entered a danger zone.
Coal is the largest source of atmospheric CO2 and the one that would be most practical to eliminate. Oil resources already may be about half depleted, depending upon the magnitude of undiscovered reserves, and it is still not practicable to capture CO2 emerging from vehicle tailpipes, the way it can be with coal-burning facilities, note the scientists, the study said.
These findings have ben published in Open Atmospheric Science Journal.