More Shadows

It's not just the barrel vaulted ceilings with shadows, it seems.  Here are some shadows in a 3rd floor flat:

Click for larger image

The resident who sent this image thinks the shadows are caused by strips of the ceiling being cooler than the rest of the ceiling, and the cool strips attracting moisture which in turn attracts dust, which in turn leaves the darker areas.

I'll ask the BEO if this shadow problem is common across the block and estate, and if so what they think is the cause and what they recommend to deal with it.