Palaeogeography, Palaeoclimatology, Palaeoecology, 21(1977): 227--235 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands POWER AND LIMITATION OF AN ENERGY-BALANCE CLIMATE MODEL AS APPLIED TO THE ASTRONOMICAL THEORY OF PALAEOCLIMATES A. BERGER Instilut d'Astronomie et de Gdophysique, Universit~ de Louvain, 1348 Louvain-la-Neuve (Belgium) (Received February 3, 1976; revised version accepted August 4, 1976) ABSTRACT Berger, A., 1977. Power and limitation of an energy-balance climate model as applied to the astronomical theory of palaeoclimates. Palaeogeogr., Palaeoclimatol., Palaeoecol., 21: 227--235. From the long-term variation of zonal annual mean air-surface temperature, computed through a global model which includes a new determination of the Earth's orbital elements and insolation and is based on Sellers' first climatic model, it is shown that the astronomical elements can only trigger and modulate the climatic changes during the last Ice Age. INTRODUCTION Because of the divergence of ideas between the followers and the opponents of the astronomical theory of paleoclimates (Milankovitch, 1941), it is essential to determine quantitatively how far the long-term variations of the ecliptical elements can account for the differentiation of the climate during the last Quaternary Ice Age. It is the aim of this paper to draw conclusions from such results obtained in studies that are or will be published in greater detail elsewhere. From a numerical analysis of the astronomical solutions used to compute the elements of the earth's orbit (described in Fig.l) over periods of time of the order of one million years or more (e.g., Vernekar, 1972), it has been shown (Berger, 1976a) that an improved solution, where some more terms are kept in the series expansion, is significantly different from the others. This solution for the eccentricity e, the longitude of the perihelion ~, the inclination i of the ecliptic on the plane of reference and the longitude of the ascending node ~2, includes terms depending on the second order to the disturbing planetary masses and on the third degree with respect to the planetary eccentricities and inclinations. The obliquity e and the general precession in longitude • are expanded (Berger, 1976b) to the second degree 227