VARIATIONS IN SUNSPOT STRUCTURE AND CLIMATE

Sunspot structure is measured by taking the ratio of the area of the umbra to that of the penumbra. The time dependence of this umbral/penumbral ratio is remarkably similar to the record of the Northern Hemisphere surface temperature anomalies. On a year-to-year basis the correlation is 0.57, which is significant at better than the 0.01% level. It is postulated that a change in the umbral/penumbral ratio is proportional to a change in the solar luminosity and that long-term variations in the luminosity lead to corresponding changes in the climate of the Earth. © 1979 D. Reidel Publishing Company.