Many years ago, when I was in elementary school, we were taught that there were naturally occurring weather cycles, they went something like this:

 

temperatures warm causing the ice cover to melt -causing the oceans to rise-causing more of the earths surface to be water-causing more warming sunlight to be reflected - causing the earth to lose heat - causing the earth to cool - causing the ice cover to build - causing the oceans to fall - causing more heat absorbing land area to be exposed to the warming sunlight - causing the earth to warm - causing etc, etc, etc., and round and round we go.