Climatic Changes, Solar Activity, and the Cosmic-Ray Production Rate of Natural Radiocarbon

Abstract

The level of the cosmic-ray-produced radiocarbon in atmospheric carbon dioxide fluctuates due to changes in the cosmic-ray intensity. These changes can be explained by considering the modulation of the galactic cosmic-ray flux by the sun. There exists a second independent correlation of the fluctuations of the radiocarbon level with changes in the climate. This correlation can best be recognized from climatic data as given by Lamb for the time since the 10th century A.D. The two kinds of correlations promise to provide a key to the understanding of solar-climatic relationships in general. The carbon-14 measurements so far carried out show that prolonged high solar activity leads to warm winters, and periods of a quiet sun lead to cold winters in Europe and elsewhere. There is reason to believe that future determinations of carbon-14 variations during the past 6000–8000 yr may supply conclusive evidence regarding the causes for the great ice ages.