That large changes in solar radiation can affect
Earth's climate is widely accepted. However, the hypothesis of
solar-induced centennial to decadal climate changes, which suggests
feedback mechanisms in the climate system amplifying even small solar
variations, has not found acceptance among orthodox climate scientists.
The climate change clique would rather place their money on greenhouse
gasses—human generated CO2 in particular. It
is true that satellite-based measurements of total solar irradiance show
that mean variations during solar cycles do not exceed 0.2 W m−2 (~
0.1% of the Sun's energy output). It has also been noted that
relatively large variations of 5–8% in the ultraviolet (UV) frequencies
can occur, though how this could change global climate remained a
puzzlement—but perhaps no longer. From studying a significant climate
shift 2,800 years ago, a group of scientists have concluded that large
changes in solar UV radiation can, indeed, affect climate by inducing
atmospheric changes.
Ask a rational and scientifically literate person
what might be the primary cause of climate change and they would be well
justified in pointing out the large bright object that passes overhead
daily. Humanity noticed that warmth came from the Sun long before it
started keeping written records. A number of primitive cultures even
worshiped the Sun as a deity. Fittingly, the Sun's possible influence on
climate has not been ignored (see “Atmospheric Solar Heat Amplifier Discovered”).
Climate scientists, however, have been loath to grant the local star
primacy of place, at least when it comes to relatively short term
climate variation.
It has been suggested by several scientists that
centennial-scale climate variability during the Holocene epoch has been
controlled by the Sun. While this sounds reasonable the problem has
always been that the amplitude of solar forcing is small when compared
with the climatic effects. Satellite measurements taken at the top of
Earth's atmosphere indicate that observed solar fluctuations amount to
less than 1/10th of a percent of total
irradiance, though the data are limited and not reliable beyond the past
30 years or so. Without more extensive and reliable data, it is unclear
which feedback mechanisms could have amplified the influence. That
situation may have recently changed.
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