Ice ages and the Milankovitch theory: A study of interactive climate feedback mechanisms

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Abstract
Several climate feedback mechanisms, which are not conventionally incorporated within climate models, are investigated to illustrate their potential role in enhancing the sensitivity of the earth's climate to changes in orbital parameters; i.e., for application to the astronomical or Milankovitch theory of ice ages. For illustrative purposes changes only in obliquity angle are considered. Specifically the feedback mechanisms which have been incorporated are: (1) Zenith-angle feedback, which constitutes a latitudinal change in the earth's zonal albedo due to the alteration in latitudinal distribution of insolation, and thus solar zenith angle, with changes in obliquity angle. (2) Bio-albedo feedback, comprising a climate-related change in surface albedo as a consequence of altered precipitation patterns modifying the vegetation of land surfaces. (3) Latent-heat feedback, which involves climate-induced changes in the poleward transport of latent heat. Employing crude parameterizations for these three feedback mechanisms within a simple climate model, it is suggested that collectively these feedback mechanisms could, by several factors, amplify climate change associated with orbital parameter variability. DOI: 10.1111/j.2153-3490.1979.tb00897.x