Paint it White.

When did we decide that having all the roofs in the world black was a good idea? I know, tar is black, and that's what many flat roofs are sealed with, but I really can't imagine a more stupid decision (is that good english)?
It's fine in the winter, when the roof becomes a giant solar heat collector. But there's no way to turn that giant solar heat collector off when the hot weather comes around.

Here in Gozo in our farmhouse we are lucky enough to have air conditioning in the master bedroom, and at the height of summer this does get used regularly, not good for global warming and certainly not good for the wallet with the cost of electricity at the moment.

Now here is the interesting part, simply painting your roof white in a hot climate could decrease air conditioning bills for those buildings by 20%. That's why California has required all new buildings to have white roofs for the past few years.
A study has shown that if the 100 biggest cities painted all their roofs white, and switched their road materials to lighter colours (ie concrete instead of asphalt) it would reflect enough light and heat back into space to entirely offset the global warming of the last few decades.
It's not a proper fix for the problem, obviously, for that, we need clean, sustainable energy. But it could buy us enough time to make the changes we really need. I feel myself going all green all of a sudden.

"He who wonders discovers that this in itself is wonder". M.C. Escher.