In 2008 a paper was published called “Short Communication – Sunshine and synoptic cloud observations at Ebro Observatory, 1910–2006” by J. J. Curto, E. Also, E. Palle and J. G. Sole.
I managed to download a copy. The following graph is of sunshine measured from an Observatory in Spain. If you weren’t paying attention you might think it is a graph of GISS or HADCRU temperatures … right?
“Since 1910, we find that there has been
an overall increase in the number of sunshine hours, but
with large oscillations that make this increase statistically
insignificant, while over the same time period cloudiness
has increased by a larger amount (about 12%) with high
We associate the increase in both sunshine hours and
cloud amount with a shift in cloud types during the
100-year period covered by the observations.”