EPS Faculty Brad Sageman Publishes New Article in Nature

EPS Faculty Brad Sageman has written a new article in Nature titled "Climate science: Predictable ice ages on a chaotic planet."

Below is the Editor's summary.

The existence of warm periods, or interglacials, in the generally cold climate of the Pleistocene epoch is well known from multiple lines of evidence. The timing of changes to the amount of solar radiation is regulated by small variations in Earth–Sun geometry. But a firm explanation for the timing of interglacials, and for the apparent changes in orbital configurations required to trigger them, has remained elusive. Chronis Tzedakis et al. now present a simple statistical model to predict interglacials on the basis of a threshold of summer insolation. The model successfully predicts the shift from glacial cycles about every 41,000 years to every 100,000 years one million years ago, and the increased likelihood of deglaciations as a function of time since the previous interglacial.

Variations in the Earth's orbit, axial tilt and precession are known to affect the amount and distribution of incoming solar radiation, and therefore climate. Numerical calculations can reconstruct these variations millions of years in the past, but theory suggests that they are inherently chaotic, making them uncertain before about 50 million years ago. Stephen Meyers and colleagues now use geological evidence from Colorado, USA to show that a chaotic shift in the orbital variation did indeed occur about 85 million years ago.

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February 28, 2017