Paleoclimates

Abstract

Evidence for large changes in Earth’s climate is well documented in geological records, and they play an increasingly important role in providing a context for modern and future climate change. Global and regional climate changes occur over all timescales due to many external and internal factors. For example, changes in Earth’s orbital configuration due to gravitational changes in the solar system affect the seasonal and geographic distribution of solar energy. Orbitally forced changes in insolation over 105 to 106 year timescales can be amplified through atmosphere-ocean interactions, influencing the concentration of atmospheric carbon dioxide (CO2) and global radiative greenhouse gas forcing. Internal factors, including dynamical changes in atmosphere-ocean circulation, changes in ice sheet and glacier mass balance, and large hydrological events such as glacial lake drainage, also influence climate. These and other processes can affect global sea level, ocean circulation and heat transport, and regional precipitation. Small changes in total solar irradiance reaching Earth’s atmosphere and volcanic events can also catalyze climate shifts over relatively short timescales.