Studies of molecules from ancient algae found in deep-sea core samples suggest that the Antarctic ice sheet was formed due to a drop in carbon dioxide levels.
This study, by Yale and Purdue universities, supports carbon dioxide’s importance in past climate change, and implicates it as a significant force in present and future climate.
The team pinpointed a threshold for low levels of carbon dioxide below which an ice sheet forms in the South Pole, but how much the greenhouse gas must increase before the ice sheet melts – which is the relevant question for the future – remains a mystery.
“The evidence falls in line with what we would expect if carbon dioxide is the main dial that governs global climate; if we crank it up or down there are dramatic changes,” said Matthew Huber, professor of earth and atmospheric sciences at Purdue.
He said that roughly a 40 per cent decrease in carbon dioxide occurred prior to and during the rapid formation of a mile-thick ice sheet over the Antarctic approximately 34 million years ago.
“We went from a warm world without ice to a cooler world with an ice sheet overnight, in geologic terms, because of fluctuations in carbon dioxide levels,” he said.
The studies were published in the journal Science.