Empirical model of the earth's response to astronomical variations of insolation.

Abstract

An empirical model of the Earth-atmosphere system is formulated from satellite observations of the response to monthly variations of insolations. Observations of reflectance at different latitude zones are portrayed as functions of insolation magnitude, its spatial gradient and variation in time during the year. Assuming heat transport and storage terms remain the same as today, conservation demands a radiant emittance (and corresponding surface temperature) which balances the energy equation. Sensitivity studies are performed to determine mean surface temperature changes associated with variations in obliquity, eccentricity, and longitude of perihelion of the Earth's orbit. Time series of temperature changes between 40 and 70oN are presented for a period form 500,000 yr before present to 100,000 yr after present. Maximum oscillations of temperature occur for obital conditions of larger eccentricity, and for longitudes of perihelion at 135o (warmest) and 270o (coldest) in the absence of positive feedback mechanisms. Periods of glacial build-up favor orbit conditions of larger eccentricity. In addition the range of the obliquity cycle may be an important factor in long-term temperature variations of the Earth. -Author