A Mechanism for Inducing Climatic Variations Through the Stratosphere: Screening of Cosmic Rays by Solar and Terrestrial Magnetic Fields

Abstract

The evidence that variations in the sun itself are responsible for climate changes is substantial and hence it is frequently suggested that the sun's near-ultraviolet radiation is significantly variable. Whether or not that inference is true, the evidence is strong that the sun's magnetically associated phenomena have long-term variations, aside from the familiar 11-year cycle. A long period of low solar activity and enhanced cosmic-ray production of NOx in the stratosphere would reduce the ozone abundance. We here offer the speculative proposition that these changes in the stratospheric composition may have led to historical changes in climate. A perturbation analysis, allowing for temperature and opacity feedbacks, is developed to indicate the kind of depletion in the O3 abundance and reduction of stratospheric solar heating that would result from an increase in NOx concentration. A pair of ?perturbation coefficients? give the reduction in O3 and temperature through the stratosphere for a specified NOx increase. This type of analysis clearly illustrates the tendency for various levels to self-heal when a perturbation occurs. Although poorly understood feedbacks make any conclusions tentative, physical arguments appear to indicate that the expected sign of the climatic effect is correct, with colder surface temperatures associated with reduced magnetic shielding. In addition, qualitative reasons are suggested for thinking significant ozone reductions by cosmic-ray influxes could lead to an increased terrestrial albedo from stratosphere condensation or to a decreased water burden of the stratosphere, which would allow more tropospheric cooling to space. It is suggested that long-term (?104 years) climatic changes may have resulted from secular geomagnetic variations while shorter (?102 years) excursions could be related to changes in solar magnetic activity. Obtaining reliable solutions to the stratospheric climate problem at the very least requires the formulation of programs that operate on both the chemical and radiative properties of the atmosphere.