CO2
http://www.space.com/18527-venus-atmosph...
Go to our National Academy of Sciences. That is why they are there.
http://nas-sites.org/climate-change/qand...
The sun. volcanoes, tectonic plate movement.
6 billion humans on earth .
There are many natural variations, including:
Ice ages, and warmer inter-glacials, are caused by Milankovitch Cycles
https://www.google.com/#q=Milankovitch+c...
PDO and ENSO (el nino / la nina) cycles cause warming and cooling.
http://cses.washington.edu/cig/pnwc/comp...
https://www.google.com/#q=enso+pdo
https://www.google.com/#q=el+nino
Low solar activity, as evidenced by low sunspot counts cause cooling.
http://en.wikipedia.org/wiki/Solar_varia...
http://solarscience.msfc.nasa.gov/Sunspo...
http://en.wikipedia.org/wiki/Maunder_Min...
Then, of course, there is the increase in energy retention caused by the 40% increase in CO2 that has occurred recently.
http://en.wikipedia.org/wiki/Global_warm...
If you can, please give me the link to where you got your information. Thanks!
