As noted by Dr. Roy Spencer,
"The most obvious way for warming to be caused naturally is for small, natural fluctuations in the circulation patterns of the atmosphere and ocean to result in a 1% or 2% decrease in global cloud cover. Clouds are the Earth’s sunshade, and if cloud cover changes for any reason, you have global warming — or global cooling."Changes in cloud cover may occur due to solar amplification mechanisms such as via solar control of cosmic ray cloud nucleation and solar modulation of ocean and atmospheric oscillations, or may occur as a negative feedback to surface warming and increased evaporation.
|The rate of warming increased by a factor of 3.8 from 1992 to 2002 corresponding to the period of "global brightening," and was followed by global cooling and a "pause" or possible "dimming" of solar surface radiation.|
The cause of solar dimming and brightening at the Earth's surface during the last half century: evidence from measurements of sunshine duration.
Gerald Stanhill et al
Analysis of the Angstrom-Prescott relationship between normalized values of global radiation and sunshine duration measured during the last 50 years made at five sites with a wide range of climate and aerosol emissions showed few significant differences in atmospheric transmissivity under clear or cloud covered skies between years when global dimming occurred and years when global brightening was measured. Nor in most cases were there any significant change in the parameters or in their relationships to annual rates of fossil fuel combustion in the surrounding 1° cells. It is concluded that at the sites studied changes in cloud cover rather than anthropogenic aerosols emissions played the major role in determining solar dimming and brightening during the last half century and that there are reasons to suppose that these findings may have wider relevance.
Clouds/aerosols control the climate, not man-made CO2
New paper finds sunshine "highly correlated" to temperature anomalies over past 50 years
New paper shows dimming of sunshine during the 1970's ice age scare, and brightening since the 1980's
New paper finds IPCC climate models unable to reproduce solar radiation at Earth's surface
New paper finds a decrease of sunshine in Iran since 2000. A cause of the 'pause'?
New paper finds solar energy at Earth's surface greatly increased between 1973 and 1998
New paper finds large increase in sunshine since the 1980's; dwarfs alleged effect of CO2
New paper finds cloudiness in Spain has significantly decreased since 1960
New paper finds 23% of warming in Europe since 1980 due to clean air laws reducing sulfur dioxide
Evidence solar radiation dominates climate change, not greenhouse gases
How climate models dismiss the role of the Sun in climate change [Part 4]