No, seriously, does it really matter whether the earth heats up, cools off or what you will. Before you cast me down with stones please consider this.
       If you believe man`s destiny is to be part of the this cosmos for ever then you must have extra-ordinary faith. Is it possible that somewhere out there, out there in the depths of space there is an enormous boulder the size of Mount Everest or bigger that will eventually collide with this insignificant planet (in respect of the Universe) and blow it to smithereens? Ten years, ten thousand years, ten million years. Enjoy your three score years and ten while you can and let tomorrow take care of itself. All the while man is on this earth he/she will find solutions sufficient for that day.