A new study published online 18 March 2012 in Nature Climate Change uses data from the Pliocene epoch to test how accurately climate models can predict future climate trends. The Pliocene epoch is the time period from 3.3 to 3.0 million years ago, and is believed to resemble most closely, in terms of “sustained global warmth,” what is predicted for the 21st century.
The Pliocene data used in the report describe sea surface temperatures, and are “newly characterized in terms of level of confidence.” Analyzing fossils from sediments that date to this time period, researchers were able to assess the veracity of temperature estimates. These temperature datasets were then used to evaluate four existing climate model simulations. “The litmus test of whether a climate model has any predictive power to tell us what future conditions might be on planet Earth in response to both natural and human climate drivers is the ability of that model to accurately predict past climate conditions as preserved in the geologic record,” says Marcia McNutt, director of the United States Geological Survey (USGS).
The researchers found that these four climate models were consistent with each other, and in agreement with the Pliocene data, with the exception of the North Atlantic region. This may be due to the complexity of the factors that affect the North Atlantic climate, including ocean circulation and atmospheric gases. Overall, this study “may provide a new perspective and insight into the predictive abilities of these models in simulating a past warm interval in Earth history.” The remaining ten general circulation models will be examined with the Pliocene data later this year.
The current work represents an international collaborative effort of the USGS with Columbia University, National Center for Atmospheric Research, University of Tokyo, Japan Agency for Marine–Earth Science and Technology, University of Leeds, British Geological Survey, and University of Bristol.