Samuel G. Philander

Knox Taylor Professor of Geosciences, Emeritus
Department of Geosciences
Climate Science
Email Address: 
Office Location: 
418A Guyot Hall

Title: Knox Taylor Professor of Geosciences, Emeritus

Area(s): Climate Science

Research Summary: Professor Philander's interest in the tropical oceans’ response to variability in winds then coalesced into George’s abiding interest in the El Niño phenomenon. By combining these insights on the oceanic response to wind variability with earlier efforts to understand how changing sea surface temperatures affected the atmosphere, a coherent picture emerged of a coupled atmosphere-ocean phenomenon: an unstable nonlinear oscillator, with atmospheric winds responding to ocean temperatures and ocean temperatures responding to atmospheric winds. George orchestrated the research of a closely knit group of colleagues that laid the foundation of the modern understanding of this phenomenon. It was the work of George and his close colleagues that made it clear that El Niño should not be thought of as a metastable state that the climate would occasionally fall into, but that it contained the seeds of its own destruction (in particular, through the equatorial Rossby waves generated during the emergence of the El Niño state) and was best thought of as a phase of a nonlinear oscillation. George (or his Spanish-speaking wife, Hilda) coined the term La Niña for the opposite phase, a term that has entered the popular lexicon. He also wrote the first modern monograph on the subject in 1990: El Niño, La Niña, and the Southern Oscillation. MORE INFO

The Precarious Present:
Is Global Warming Inhibiting an Incipient Ice Age?

Abstract: The amplifying climate fluctuations of the past 3Myr indicate that an Ice Age is imminent, except that the current rise in atmospheric CO2 levels is inducing global warming. Forecasts of future developments by means of climate models, a reductionist approach, have significant uncertainties. Empirical predictions are also inadequate because an explanation for Ice Ages is lacking, a consequence of the questionable assumptions that polar glaciers respond primarily to local sunlight, and that the ocean obligingly provides them with fresh water which the atmosphere passively transports from low to high latitudes. These objections draw attention to the global structure of Milankovitch forcing whose main components pose the following questions. (a) How does precession, which merely redistributes sunlight over the course of a year without changing the annual average induce a 20Kyr signal? (b) How do 40Kyr obliquity oscillations, which merely redistribute sunlight spatially without changing the global average, induce 40Kyr oscillations in globally averaged temperature? (c) Could the alternating warming and cooling trends of the sawtooth signal of the past .8Kyr, and the preceding cooling trend from 3 to 1Myr, be a natural (as opposed to forced) climate mode with feedbacks sustaining trends which thresholds reverse? (The signal would be irregular, except that Milankovitch forcing is the pacemaker of its thresholds.) This reassessment of studies of past and present climates leads to tentative explanations for Ice Ages, offers a strategy for improving climate models, and predicts that rising CO2 levels will restore the “permanent” El Niño of 3Myr ago.

by S. George Philander and Marcelo Barreiro


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