yes i've heard that explanation before, it doesn't really wash - just how variable can the same skies be at the same minute?

it's the effects of the trails. if you're up early in spring/ summer, and see clear blue skies - then see these 'persistent contrails' leaving huge white lines across the sky, you will soon see the sky becomes matt grey, sun blocked out, very often (not always.) ice crystals don't do that.

the best evidence is that which you see for yourself. peace.