Palaeoclimatology (or paleoclimatology) is the study of changes in climate over the entire history of Earth. Modern interest in climate change has caused a great increase in the climates of the past.

The climates of the past can only be studied by proxy. Data comes from studying rocks, sediments, ice and tree rings, corals, shells and microfossils. These records are used to work out the past states of the Earth's climate and its atmospheric system.