Onto the ice ages: proxy evidence for the onset of Northern Hemisphere glaciation
Published:January 01, 2007
A. C. Ravelo, K. Billups, P. S. Dekens, T. D. Herbert, K. T. Lawrence, 2007. "Onto the ice ages: proxy evidence for the onset of Northern Hemisphere glaciation", Deep-Time Perspectives on Climate Change: Marrying the Signal from Computer Models and Biological Proxies, M. Williams, A. M. Haywood, F. J. Gregory, D. N. Schmidt
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Global climate change over the last five million years includes the early Pliocene warm period (c. 5–3 Ma) and a transition to the cool ice age climate of the latest c. 2 Ma. The growth of large ice sheets was accompanied by changes in deep and intermediate water mass characteristics, the end of El Niño-like mean conditions, and the development of cool tropical and subtropical upwelling regions. By considering how and when regional changes occurred, several possible causes of the warm to cold Pliocene climate transition are explored. There is intriguing evidence that, in addition to ice-albedo feedbacks that amplified cooling in high-latitude regions, the shoaling thermocline was a critical factor in the evolution of the Northern Hemisphere ice ages.
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Deep-Time Perspectives on Climate Change: Marrying the Signal from Computer Models and Biological Proxies
This book unites climate modelling, palaeoceanography and palaeontology to address fundamental events in the climate history of Earth over the past 600 million years. Understanding the ‘tipping points’ that have led to rapid changes in the Earth's climate is vitally important with the realization that humans modify global climate. In an effort to better understand past and future climate change, general circulation models have become the forerunners of attempts to simulate future climate. Although extraordinarily sophisticated, they remain imperfect tools that require ‘grounding’ in geological data. In this, the study of past major climate transitions like the Palaeozoic icehouse worlds and the extreme greenhouse of the Cretaceous are invaluable. Both the mechanisms that forced changes in the Earth's climate as well as the proxies that track these changes are discussed. The central message of the book is that general circulation models tested with geological data in an iterative ‘ground truth’ process provide the best estimates of the Earth's ancient climate.