If shit gets too hot on Earth this will solve the problem quickly and efficiently: a large satellite placed in orbit around the sun exactly between the Sun and Earth designed to spread out a giant solar shield (just a thin sheet of foil blanket) will reflect light back at the Sun and prevent any light from reaching Earth. Leave the shield open for a full 24 hours and then close it. The temperature on Earth should be sufficiently reduced during this time to help out the planet, just don't leave it open too long or the planet will freeze over.

How large (m^2) of a shield is required at what distance to block all sunlight from reaching Earth?