Incog_Neeto: So if you painted every roof in the world with this paint would it have any appreciable effect on global warming?

If you can devise someway to keep it clean and maintain it's ability to stay sub-ambient through radiation, then probably, yeah. That would take a big whack at residential a/c power consumption at least. Dunno if the albedo change is over enough square footage that it would significantly impact the planetary warming, but I suppose it could be. Seems unlikely that we've got enough roof to make up for losing the insane amount of ice coverage that has disappeared over the last few decades.

dionysusaur: Lexx: Hospitaller: Is this ultra-white paint developed using Titanium Dioxide?  Because that leads to soil contamination with Dioxins

Barium sulfate.

Reflective surfaces that also radiate have huge potential with regards to passive cooling.  Radiated heat mostly goes to space - so you not only cool the environment but that heat doesn't even get transferred to the external environment.

Assuming it gets past the methane & CO2.

That's largely the point of this stuff, it radiates in a region they don't absorb in. And while the first stuff this effect was demonstrated with was barium sulfate, this iteration is boron nitride based.

Gleeman: In the Navy we'd paint the top decks of the ship white when going to the Persian Gulf. Not sure if it made a real difference in internal temperatures when the water the ship was floating in was ~90F.

I did a wee bit of time there on a submarine that was built to chase Rooskis around the north Atlantic. It got extraordinarily sweaty.