Substitute. Paleoclimatologists use proxy evidence in place of direct measurements of climate parameters such as temperature, for times before instrumental measurements were made. Ocean sediments, glacial ice, and tree rings all contain proxies for climate conditions.
A proxy climate indicator is a local record that is interpreted, using physical and biophysical principles, to represent some combination of climate-related variations back in time. Climate related data derived in this way are referred to as proxy data. Examples of proxies are: tree ring records, characteristics of corals, and various data derived from ice cores. ()
In climate research, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained. Temperature proxies such as tree ring widths and ice core layering are used by climatologists to create a temperature record.