Palaeoclimate

Palaeoclimate refers to the climate conditions that prevailed in the past, before instrumental records. It is reconstructed from physical, chemical, and biological indicators preserved in rocks, ice, sediments, and biological materials, and from climate models that simulate past conditions. The study aims to describe long-term variability, periodicities, and abrupt shifts in temperature, precipitation, and related aspects of the climate system.

Proxies provide indirect evidence. Tree rings reveal growing-season conditions; ice cores store trapped air and isotopic signals; marine and lake sediments preserve assemblages and isotopic ratios; speleothems (cave minerals) yield rain and cloud patterns; pollen and spores indicate past vegetation. Stable isotopes, especially oxygen-18 and carbon-13, serve as temperature and carbon-cycle indicators. Dating methods include radiometric techniques, radiocarbon for younger records, dendrochronology, magnetostratigraphy, and biostratigraphy.

Reconstruction combines proxy data with statistical methods and climate models to estimate past temperatures, precipitation, and greenhouse-gas concentrations over timescales from thousands to hundreds of millions of years. Notable intervals include the last glacial–interglacial cycles of the Quaternary, the warm Eocene, the Cretaceous greenhouse world, and rapid events such as the Paleocene–Eocene Thermal Maximum.

Interpretation focuses on climate drivers such as orbital variations, volcanic eruptions, carbon-cycle feedbacks, and tectonic changes that alter ocean and atmospheric circulation. Uncertainties include proxy biases, geographic sampling gaps, dating errors, and the need to align different proxies into coherent reconstructions.

Palaeoclimate research informs understanding of natural climate variability, tests and calibrates climate models, and provides context for assessing anthropogenic climate change by comparing present trends with the range of natural variability observed in the geological record.