Frontiers of geophysics

Abstract

The present and future state of geophysics was the subject of five wide‐ranging talks at “Frontiers of Geophysics,” a Union session held May 18 at the AGU Spring Meeting in Baltimore, Md.Scientists have suspected for many years that solar radiation controls aspects of Earth's climate. An up‐to‐date look at this old scientific problem led off the session. John Imbrie of Brown University (Providence, R.I.) talked about climatic effects of variations in Earth's orbital elements, better known as Milankovitch cycles. Three components of Earth's astronomical motion contribute to the amount of solar energy that reaches Earth: the obliquity or tilt of the rotation axis, its conical wobble or precession, and the eccentricity of Earth's orbit. The periods of these orbital elements vary from 23,000 years for precession to ∼100,000 years for eccentricity. The Milankovitch theory has now been tested against a rapidly growing mountain of climate and paleoclimate data and applied to t h e recurrence of ice ages and other phenomena.