Lost track of this. We‘ve established that cloud coverage is declining and that clouds likely have a cooling effect on surface temperatures.

You asked why there is less cloud coverage. As a matter of fact, CERN (and other scientists) proved in theory and practice that cloud coverage is influenced by cosmic radiation (from the galaxy as well as the sun). https://home.cern/news/news/experiments/cosmic-rays-clouds

There are solar cycles with increases and decreases in solar activity. In the past 40 years or so, solar activity decreased which likely had an impact on cloud coverage (less clouds due to less solar radiation) and, hence, surface temperatures (higher due to less clouds) on earth.

Yet, this path of scientific research is not at all discussed by climate scienists. 

What I am trying to say is: the earth‘s climate is way too complex and we know way too little about it to pinpoint it to one factor alone. And even worse so, real open-ended scientific research on the matter is discouraged. It‘s a taboo and could cost you your career as a scientist.