The ice provides the best means of determining the composition of the atmosphere before recent decades.
Radiocarbon is produced naturally by cosmic rays.
The most recent air available from the ice is from the late 1970s. At that time, Divisional scientists began setting aside samples of pristine air collected at Cape Grim in north-western Tasmania. This process will allow scientific groups from around the world to properly pool their resources, knowing that measurements from, for example, Australia, can be directly compared with those from the United States. An international network of global atmospheric data will be most valuable to researchers examining, for example, changes to greenhouse gas levels. I could see that one day we might be interested in measuring gases that at the time we were either not measuring or incapable of measuring,' Dr Fraser recalls.