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Alfred H. Pekarek1
(1) St. Cloud State University, St. Cloud, MN
Abstract: 
Solar
forcing of Earth's climate
The sun is the primary source of
energy for the climate of the earth. Variations in solar energy reaching the
earth's surface change the climate. Several factors control the influx of solar
energy including (1) variations in the earth's albedo, (2) variations in
earth's orbit and rotation, and (3) variations in solar energy output.
In the short time since 1978,
direct measurement of total solar irradiance (TSI) by satellites has shown
cyclical variations in solar energy of 0.1% in conjunction with the eleven year
sunspot cycle. Indirect evidence from the Sun and other sun-like stars
indicates that TSI has had significantly greater variation as the Sun goes
through various cycles.
The correlations between climate
and TSI variations are statistically solid. Small variations in TSI initiate
indirect mechanisms on earth that yield climate changes greater than that
predicted for the TSI change alone. At least three solar variables are known to
affect earth's climate: (1) TSI, which directly affects temperatures; (2) solar
ultraviolet radiation, which affects ozone production and upper atmospheric
winds; and (3) the solar wind which affects rainfall and cloud cover, at least
partially through control of earth's electrical field. Each affects the earth's
climate in different ways, producing indirect effects that amplify small
changes in TSI. Individually, they do not cause the entire observed climatic
changes. Collectively, they appear sufficient especially since solar forcing of
earth's climate is still an emerging science. Undoubtedly, other mechanisms of
solar
forcing are poorly understood, perhaps even unknown.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana