May 15, 2013
Warming In China Four Times Greater Than Previously Thought
Brett Smith for redOrbit.com - Your Universe Online
According to new research in the Proceedings of the National Academy of Sciences (PNAS), average temperatures in central China are 10 to 14 degrees Fahrenheit hotter today than they were during the last Ice Age 20,000 years ago.
"Previously, we could only infer temperature on land through changes in climate archives like tree rings or pollen over time," said lead author Robert Eagle, a UCLA climatologist. "This is the first time that temperature has been determined accurately on land at the time of the last ice age."
To reach their findings, the scientists discovered slight atomic differences in the calcium carbonate found in rocks and fossilized snail shells.
"We can now tell what temperatures were on land 20,000 years ago with more accuracy than was ever previously possible," senior author Aradhna Tripati, an earth and space professor at UCLA, said in a statement.
In the study, researchers collected two major sample types, fossilized snail shells and soil deposits, from a wind-swept plateau in central China. An analysis dated the sample back to about 20,000 years ago.
"One of the most important aspects of the study was showing that we could get the same result from such different types of carbonates," Tripati said. "Even though these materials integrate over very different time frames, they gave us the same result."
When the team compared their findings to established climate models for central China, they noticed that those models that accounted for atmospheric processes tended to be the most consistent with their calcium carbonate analysis.
"The climate models that did the best job of resolving temperature changes in this region were the ones that accurately depicted very large-scale atmospheric processes, such as patterns of winds in the atmosphere, the position of the jet stream and various atmospheric fronts," Tripati said. "The models that didn't resolve these atmospheric phenomena tended to do a poorer job of predicting temperature."
"It's so important to have models that accurately depict regional climates on land for the study of past and future climate change,” she added. “We were surprised at how poorly most climate models predicted temperature change in central China and also surprised at how sensitive this region has been to changes in climate forcing."
Since the last Ice Age, there has been a steady rise in greenhouse gases and other atmospheric factors, changing how solar radiation impacts the Earth's surface.
"We have not dissected out the specific role of greenhouse gases, such as carbon dioxide, in this study, but they are certainly a contributing factor to temperature change and ice-sheet extent," Eagle said.
The researchers noted that similar sediment types in the Midwestern US could be used for a similar analysis and the UCLA scientists are currently repeating their methods using the American samples.