BRISTOL, England, Dec. 7 (UPI) -- British scientists say the Earth might be up to 50 percent more sensitive to atmospheric carbon dioxide than has been estimated.
University of Bristol researchers, led by Dan Lunt, said their study shows components of the Earth's climate system that vary over long timescales -- such as land-ice and vegetation -- have an important effect on temperature sensitivity, but such factors are often neglected in current climate models.
The researchers said they compared results from a global climate model to temperature reconstructions of the Earth's environment 3 million years ago when global temperatures and carbon dioxide concentrations were relatively high.
"We found that, given the concentrations of carbon dioxide prevailing 3 million years ago, the model originally predicted a significantly smaller temperature increase than that indicated by the reconstructions," Lunt said. "This led us to review what was missing from the model."
The study showed the increased temperatures indicated by the reconstructions can be explained if factors such as land-ice and vegetation are included in the model. That, the scientists said, is primarily because changes in vegetation and ice lead to more sunlight being absorbed, which in turn increases warming.
Alan Haywood, a study co-author from the University of Leeds, said the findings show studying past climates can provide important insights into how the Earth might change in the future.
The research appears in the journal Nature Geoscience.
