Not sure whether this research has been covered on this ng already
but
Imperial College and Colorado have got together to study this old
chesnut. Although the effect of solar activity on the Earth's
atmosphere has been Joanna Haigh's claim to fame for a long time.
Summary: A decline in solar activity leads to a warmer Earth.
There is a lack of detail in the press release below, I suppose you
need to read the paper in 'Nature' for more info. Surprised they
published it on so few years data.

http://www3.imperial.ac.uk/newsandev...%3Dsun_climate

Len Wood
Wembury, SW Devon