A little of 1 & 2.  I don't know that they are corrupt, but they certainly chase grant money, and when that is awarded by a federal gov't and NGO's that are more interested in the outcome than the science, it will skew answers they produce. 
The people that wield the results of the studies as a political sword are driven by a socialist, anti-capitalist agenda.
  Yes, there a is a greenhouse gas effect.  There are also many other variables at play that are neither well understood and often neglected. The system as a whole needs to be studied, not just the things that will give the pre-determined answers the  they want.