Sorry, but this is not a joke. It is intended to give you websites that can help evaluating insolation.

You see, agriculture and solar power need sun light, but man’s activities also take away sunlight - thus the issue of global warming is not the whole story. There is also an issue about decreased insolation.
Clouds in the sky are not just an issue of esthetics and the vanished blue sky of California may yet cost in terms of alternate energy and in crop yields.