Paleoclimate
Paleoclimatology is the study of climate prior to the widespread availability of records of temperature, precipitation and other instrumental data. NOAA is particularly interested in the last few thousand years because this is the best dated, best sampled part of the past climatic record and can help us establish the range of natural climatic variability in a period prior to global-scale human influence.
Environmental recorders are used to estimate past climatic conditions and thus extend our understanding far beyond the 100+ year instrumental record. "Proxy" records of climate have been preserved in tree rings, locked in the skeletons of tropical coral reefs, extracted as ice cores from glaciers and ice caps, and buried in laminated sediments from lakes and the ocean.