"If our results are correct, the total carbon emissions required to stay below 2 degrees of warming would have to be three-quarters of previous estimates, only 750 billion tons instead of 1,000 billion tons of carbon," said Frlicher, now a researcher at the Swiss Federal Institute of Technology in Zurich. "Thus, limiting the warming to 2 degrees would require keeping future cumulative carbon emissions below 250 billion tons, only half of the already emitted amount of 500 billion tons."
The researchers' work contradicts a scientific consensus that the global temperature would remain constant or decline if emissions were suddenly cut to zero. But previous research did not account for a gradual reduction in the oceans' ability to absorb heat from the atmosphere, particularly the polar oceans, Frlicher said. Although carbon dioxide steadily dissipates, Frlicher and his co-authors were able to see that the oceans that remove heat from the atmosphere gradually take up less. Eventually, the residual heat offsets the cooling that occurred due to dwindling amounts of carbon dioxide.
Frlicher and his co-authors showed that the change in ocean heat uptake in the polar regions has a larger effect on global mean temperature than a change in low-latitude oceans, a mechanism known as "ocean-heat uptake efficacy." This mechanism was first explored in a 2010 paper by Frlicher's co-author, Michael Winton, a researcher at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory (GFDL) on Princeton's Forrestal Campus.
"The regional uptake of heat plays a central role. Previous models have not really represented that very well," Frlicher said.
|Contact: Morgan Kelly|