One-million-year-old air extracted from bubbles in an Antarctic ice core has enabled the reconstruction of the oldest atmospheric compositions yet studied.

Glaciers flowing over raised bedrock in Allan Hills, Antarctica, brought long-sought-after blue ice near to the surface, providing an accessible source of ancient air. John Higgins at Princeton University in New Jersey and his team measured, among other gases, the carbon dioxide and methane content of this trapped air. The findings indicate that the strong link between atmospheric greenhouse gases and the Antarctic climate observed for the past 800,000 years extended to at least one million years ago.

Proc. Natl Acad. Sci. USA (2015)