I study past climate and environment, mainly from polar (Antarctic and Greenland) ice cores. Ice in the polar regions preserves a unique chronological archive of information about the past. This extends so far 800,000 years in Antarctica and 128,000 years in Greenland. In collaboration with the British Antarctic Survey (also in Cambridge) and colleagues overseas, I collect ice cores, analyse them, and draw conclusions about the mechanisms of climate change.

The ice builds up year by year and stores information in three main ways: the isotopic content of the water molecules themselves tell us about past temperature; soluble and insoluble impurities trapped on the snow surface and in snowflakes record information about aspects such as past volcanic eruptions, sea ice extent, and biomass burning; finally air bubbles trapped in the ice record atmospheric composition including past greenhouse gas concentrations.