There have been instances in Earth history when average temperatures have changed rapidly, as much as 10 degrees Celsius (18 degrees Fahrenheit) over a few decades, and some have speculated the same could happen again as the atmosphere becomes overloaded with carbon dioxide. New research lends support to evidence from numerous recent studies that suggest abrupt climate change appears to be the result of alterations in ocean circulation uniquely associated with ice ages. "There might be other mechanisms by which greenhouse gases may cause an abrupt climate change, but we know of no such mechanism from the geological record," said David Battisti, a University of Washington atmospheric sciences professor.