Okay that's what I thought.
Q: "Why does gravity vary with altitude?"
A: The moon and stars have a slight gravitational pull.
I thought the theory was these bodies were above the Earth?
Again, TheEngineer is a much more reliable source of FE theory than myself, but I'll take a crack at it.
I believe that because the stars and the moon are above the Earth, their slight gravitational pull affects objects differently at different altitudes. Meaning you'd weigh less on the top of Mount Everest because the stars are pulling you up more, not because the Earth is pulling you down less.
As for the global warming part, I personally don't. But I don't know if that is the official opinion of the FES.