Bagging ice cores. Photo: Doug Thost

As the snow falling in Antarctica is buried and compressed into ice, Antarctica's ice sheet is built up over hundreds of thousands of years. Australian scientists have drilled more than a kilometre into the ice sheet to ice that fell as snow 50,000 years ago. The ice cores they have extracted contain dust, chemicals and bubbles of air that have been trapped in the ice. These demonstrate profound changes in earth's climate and in atmospheric chemistry, from the ice age to the present warm and stable conditions, as a result of natural and human activity; such as the inexorable rise in atmospheric carbon dioxide content since the industrial revolution. The information derived is fundamental to our understanding of global climate change and to judge how present human activities could affect the climate system in the future.

• Ask students to find out what scientists have discovered by studying ice cores that have been taken from the Antarctic ice cap. Read the article volcanic eruptions and solar activity detected in ice core. In addition, on the Antarctic Division's site is an explanation of a project undertaken in 2004-05 Little Ice Age: Big Effort.