Climate – the mean and range of temperature and precipitation prevailing over a defined area of the globe – is complex in its causation and expression. Reconstructing climate, the effort to describe and measure climates of the past, must necessarily be a complex and technical undertaking. Climates leave only indirect, proxy evidence of their past states and conditions. The reconstruction of past climates, therefore, requires accumulation of indirect and partial evidence from many diverse sources, which must be carefully evaluated and compared. Archaeology and archaeologists contribute important sets and classes of data to the undertaking, but the task of reconstructing climate is not archaeological. It requires the integration of data from many sources by means of concepts and techniques that are themselves interdisciplinary.

The reconstruction of ancient climates involves specification of the distributions and amplitudes of temperature and precipitation in space and time. Once an exercise in inspired analogy, paleoclimatic study entered a dynamic phase in the 1970s, when the Earth's orbital and axial variations were demonstrated to be fundamental forcing factors for large-scale climatic states (Chapter 3). With basic mechanisms identified, paleoclimatology has been a lively research frontier since the 1980s. No survey such as this can be either complete or current. This chapter is an introduction for archaeologists, who may then explore further in the specialist literature.