Typically I can't find any reliable stats on the spot, but I recall the reduction in photosynthesis from ordinary heavy cloud cover alone can be up to 85% - wit

Typically I can't find any reliable stats on the spot, but I recall the reduction in photosynthesis from ordinary heavy cloud cover alone can be up to 85% - with most photosynthesis happening whilst there is only light (or even no) cloud cover. Probably this would have minimal effect on light cloud cover and there is already not a great deal happening during heavy cloud.