A research group formed by 64 researchers from the National Institute of Polar Research, the University of Tokyo, and other organizations has analyzed atmospheric temperatures and dust for the past 720,000 years using an ice core obtained at Dome Fuji in Antarctica. Results indicate that when intermediate temperatures occurred within a glacial period, the climate was highly unstable and fluctuated. A climate simulation was also performed based on the Coupled Atmosphere-Ocean General Circulation Model, which revealed that the major cause of the observed climate instability was global cooling caused by a decline in the greenhouse effect.