Wednesday, August 15, 2012

Earth's Climate Follows The Sun's UV Groove

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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