Thursday, October 30, 2014

Comment on Mcleans Paper " Late Twentieth-Century Warming and Variations in Cloud Cover"

This comment was posted on WUWT on10/30/14

The post and cooling forecast at
has this to say about the sun and climate.
"NOTE!!  The connection between solar "activity" and climate is poorly understood and highly controversial. Solar "activity" encompasses changes in solar magnetic field strength, IMF, CRF, TSI, EUV, solar wind density and velocity, CMEs, proton events etc. The idea of using the neutron count and the 10Be record as the most useful proxy for changing solar activity and temperature forecasting is agnostic as to the  physical mechanisms involved.
Having said that, however, it is reasonable to suggest that the three main solar activity related climate drivers are:
a) the changing GCR flux - via the changes in cloud cover and natural aerosols (optical depth)
b) the changing EUV radiation - top down effects via the Ozone layer
 c) the changing TSI - especially on millennial and centennial scales.
 The effect on climate of the combination of these solar drivers will vary non-linearly depending on the particular phases of the eccentricity, obliquity and precession orbital cycles at any particular time.
 Of particular interest is whether the perihelion of the precession falls in the northern or southern summer at times of higher or lower obliquity."
I am gratified to note that the McLean paper provides strong support for a) above. Closer investigation into the exact processes involved in the solar magnetic field strength -GCR -cloud connection should prove fruitful.
It highly significant that the sharp decline  in the 0-30 N and 0-30 S cloud cover (Fig 10) ends at about the same time as global warming stops.
It is also of interest to note the almost coincident drop to what looks like a new baseline in the Magnetic Plage Strength Index.see p34 in Leif Svalgaard's
1610  Solar-Activity-Past-Present-and-Future.ppt (TIEMS Conference, Oslo, Norway, 2012) pdf pdf with notes
The McLean paper is at