An ancient crater lake in Central Otago has given a Kiwi scientist a unique insight into how quickly climate change could cause the Antarctic ice sheet to melt.
Fossilised leaves found at Foulden Maar near Middlemarch have been found to contain evidence of a sharp increase in atmospheric CO2 levels associated with a major collapse of the ice sheet 23 million years ago.

University of Waikato paleoclimatologist Dr Beth Fox and colleagues from Columbia University in New York calculated the CO2 levels by studying stomatal cells and carbon isotope ratios in the fossils.

They found CO2 levels rose from about 500 parts per million (ppm) to up to 1550ppm over a geologically short span of less than 10,000 years.