There has been much debate in the literature regarding the
influence of solar variability on the climate of the earth at
decadal to centennial timescales. Early work by Mock and
Hibler [1976] and Roberts and Olson [1975] attributed
oscillations in the North American winter temperature record and
periodicity of droughts in the midwestern United States to the
double sunspot cycle, respectively. Recently, Hood et al.
[1993] used satellite data to explore the relationship between
solar activity and stratospheric temperature, ozone concentrations,
and zonal winds. Although the available record is short,
the independent measures of temperature and ozone covaried with
long-term solar variability. Keeling and Whorf [in press]
tried to determine the mechanism responsible for decadal
variability in surface temperature and tropospheric CO
concentrations. They concluded that solar forcing by itself was
not sufficient, but may contribute to oscillations in observed
temperature (with 9-10 year periodicity), possibly in conjunction
with ENSO events.