Chemical fossils
Andy Extance finds out what organic molecules made by microorganisms and plants far in the past can tell us about climate
Reconstructing what the climate was like in the past takes some clever chemistry – and a little help from mud and microbes. Certain microorganisms produce lipids which they need to be stay as fluid as possible. This means that they slowly evolve to produce different lipid molecules at different temperatures. Scientists can look for these lipids in tiny flecks of mud in polar ice cores and use them to deduce what the temperature was like when the ice was formed, many thousands of years ago.