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Why can orbital variations alone not explain the full size of Pleistocene climate changes?
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Quaternary
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the Quaternary Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
While orbital variationsāoften called the "pacemaker" of the ice agesāare fundamental to driving Quaternary climatic cycles, they cannot explain the full magnitude of Pleistocene climate changes on their own. The seasonal and latitudinal variations in solar radiation produced by these orbital parameters are relatively small, necessitating the operation of complex feedback mechanisms to amplify these signals.12
Key feedback processes that amplify these climatic shifts include:
- Albedo: The growth of continental ice sheets increases Earth's reflectivity, reducing the absorption of sunlight and leading to further cooling.12
- Greenhouse Gases: Fluctuations in atmospheric carbon dioxide and methane concentrations act as a significant amplifier; their reduction during glacial transitions reinforces cooling, while their increase during interglacials promotes warming.12
- Vegetation Changes: Shifts in land cover, such as the replacement of forests with tundra, alter both albedo and the release of latent heat through evapotranspiration.2
- Ocean-Atmosphere Dynamics: Major reorganizations of the ocean-atmosphere system, including changes in thermohaline circulation and heat transport, are also critical to explaining the observed climatic record.13