CoachA climate archive is a natural material laid down in layers, one after another, that keeps a trace of the climate of the time it formed: polar ice, the sediments of lakes and of the ocean floor, the rings of trees, corals, cave deposits. A proxy is a quantity measured in an archive that stands in for a climate variable that was not measured: the share of heavy isotopes in old snow for the air temperature, the share of each kind of pollen in lake mud for the vegetation and so for the climate.
| archive | proxy | tells about |
|---|---|---|
| polar ice | heavy isotopes of the ice | air temperature over the ice |
| air in the bubbles | carbon dioxide, methane | |
| lake sediments, peat | pollen | vegetation, then climate |
| ocean sediments | oxygen isotopes of shells | ice volume, deep-water temperature |
| tree rings | ring width | growing conditions, year by year |
| corals, cave deposits | isotopes, growth bands | sea or air temperature, rain |