PRECED_G PAGEBLANKNOT FILMED Preface

The total solar power reaching the Earth is probably the most critical l parameter external to the atmosphere which affects our climate. The question of the constancy of the so-called solar constant, or solar irradiance, has been addressed for nearly a century. However, for a variety of atmospheric and instrumental limitations, a definitive answer has remained elusive. The investigators who work on the problem of the solar constant come from very different scientific backgrounds and use very dissimilar techniques. However, this wealth of approaches has not been fully utilized since each group often ignores the efforts of the other groups which use different techniques. When the organieing committee of this workshop first met in Spring 1980, we had in mind a number of developments which had brought this old problem again into focus. First of all, rocket-borne and balloon-borne instruments kept producing changing values of the solar constant. Secondly, indirect techniques had been proposed to monitor the solar constant, and they also suggested the occurrence of changes. Unfortunately, not only the magnitude, but even the sign of these changes were not very consistent with each other, suggesting that a straightforward interpretation of the results was not warranted. Finally _ for the first time we had two spacecraft in orbit, Nimbus-7 and the Solar Maximum Mission, which could give simultaneous readings of the solar constant, and thus check the validity of each other's results. It was clear that all the workers in this subject had to talk to each other, and so the Workshop on the Variations of the Solar Constant was arranged to take place at the Goddard Space Flight Center of NASA, between the 5th and the 7th of November 1980. The following Proceedings include all the papers read at the Workshop which had not been published elsewhere. The result is a substantially complete discussion of the solar constant problem as understood at the end of 1980. ii