A study showed that vast Antarctic glaciation was caused by global cooling, according to a news release issued by the University of Hong Kong on Thursday.
Global climate rapidly shifted from a relatively ice-free world to one with massive ice sheets on Antarctica about 34 million years ago. A team of scientists from research units from different countries and regions offered a new perspective on the nature of changing climatic conditions across this greenhouse-to-icehouse transition, which has important implications for predicting future climate changes.
Detailed in the latest issue of Science, an international scientific journal, the data disproved a long-held idea that massive ice growth in the Antarctic was accompanied by little to no global temperature change.
The report showed that before the Southern Hemisphere ice expansion, high-latitude temperatures were at least 10 degrees Celsius warmer than previously estimated and that there was a 5 to10 degrees Celsius drop in surface-water temperature during the climate transition.
"Temperatures in some regions, just before the Antarctic glaciers formed, were surprisingly higher than current climate models predicted, suggesting that these models underestimate high-latitude warming under high carbon dioxide conditions," said lead author Dr. Zhonghui Liu, assistant professor at the University of Hong Kong.
Further, he said, the substantial cooling that occurred in both Northern and Southern high latitudes suggests that a decline in carbon dioxide level, rather than a localized change of ocean circulation drove the climate transition.