The Earth is a closed system.. Global warming is pretty much bullshit, and almost all weather upswings and temperature changes are part of a cycle that has been going on since long before documented history. The "shocking and upsetting" weather trends that people use to uphold the global warming theory are actually not at all unusual in earth's climatological history, and are in actuality part of a cycle.
http://users.erols.com/dhoyt1/
http://www.aim.org/publications/brie...27mar2002.html
http://capmag.com/article.asp?ID=212
http://web.tampabay.rr.com/skaw/globalwarming.html
http://www.meteor.iastate.edu/gccour...2/seedsci.html