IN late August of 1998 two major solar arrays in the Nevada desert were perplexed by a three to five percent drop in their collected energy. The usual suspects were checked, dirt, rain, clouds, smoke, etc. None of these were identified as the cause.
NASA's ACE space craft had registered a rather odd shift in the solar spectrum which was ignored. It was a shift in energy output drop from 0.2um-0.5um and a corresponding increase around 1.0-1.2um. So subtle that no one even cared, except engineers of solar panels. The band pass of PV panels, which it converts to energy, is primarily in the 0.3 to 0.6 um wave length.
The Cause was a SPECTRAL SHIFT originating on the sun. The energy was simply not making it to earths surface.
How will this type of change affect earths energy balance and its climate engine?