Climate science
Paleoclimate
Definition
Paleoclimate refers to the climate of past geological and historical periods, reconstructed using natural archives — ice cores, tree rings, lake and ocean sediments, corals and speleothems — whose physical and chemical properties record temperature, precipitation and atmospheric composition. These proxy records extend climate knowledge far beyond the instrumental record.
References
proxy evidence and paleoclimate context for current warming
archives, proxies and methods
Overview
What it means
Paleoclimate evidence shows that current atmospheric CO₂ concentrations are unprecedented in at least hundreds of thousands of years, and that present warming is faster than most natural changes in the record. Past warm periods also constrain estimates of how the Earth system responds to greenhouse gas forcing, including sea level and ice sheet behaviour.
How it is used
Paleoclimate reconstructions underpin IPCC assessments (including the "hockey stick" temperature reconstructions), calibrate climate models, and define pre-industrial baselines used in the Paris Agreement temperature goals.
Why it matters
Without the paleoclimate baseline, the unusualness of modern warming cannot be established; the field turns geological evidence into the context that makes climate change measurable and attributable.