How the little-known 'dark roof' lobby may be making US cities hotter

Years ago I wanted to cool a second-floor apartment I lived in (the top floor of a two-floor house) a bit during the summer, and decided on the simple solution of painting its entire flat roof with white rain-proofing sealant.

It worked, and was useful as far as that goes, but for someone who also used their flat roof as a terrace for barbecues and etc, there was one very obvious drawback that I so obviously should have foreseen: On a sunny day, forget about relaxing up there. The reflective glare was enough to induce something like snow blindness.

It's interesting to see the Guardian using Fahrenheit ("50 degrees hotter") here. Unless it really is an entire 50 degrees C? I suppose that's plausible.

It's co-published with an American group, though, and they also use 50.

It'd be nice if they were more explicit.