A study of two methods for reconstructing ancient temperatures has given climate researchers a better understanding of how cold it was in Antarctica during the last ice age around 20,000 years ago. For decades, the leading science suggested ice-age temperatures in Antarctica were on average about 9 degrees Celsius cooler than at present. An international team of scientists led by Oregon State University’s Christo Buizert has determined that while parts of Antarctica were as cold as 10 degrees below current temperatures, temperatures over central East Antarctica were just 4 to 5 degrees cooler. The findings were published this week in Science. In the study, researchers used ice cores from seven locations across Antarctica – five from the East and two from the West. The borehole thermometry method measures temperatures throughout the thickness of an ice sheet. The Antarctic ice sheet is so thick that it keeps a memory of earlier, colder ice age temperatures that can be measured and reconstructed, said T.J. Fudge, an assistant professor in the department of earth and space science at the University of Washington. The second method examines the properties of the snowpack as it builds up and transforms into ice over time. In East Antarctica, that snowpack can range from 50 to 120 metres thick and has compacted over thousands of years in a process that is sensitive to temperature changes. The researchers found that both methods produced similar temperature reconstructions, giving them confidence in the results.