Really, it seems to me that the only way to completely determine one way or another would be to:
Place temperature, pressure, energy, and molecular (as in, what molecules are in the area) sensors on a 25 meter (or would 250 meter be more reasonable?) spacing in a 3-D grid covering the entire surface of the earth and extending up to geosynchronous orbit.
Tie it to the Sats there with large ribbons.
Of gold foil covered cloth, to protect against sunlight.
Use data collected from such to prove or disprove theories as to how various gasses produced (or not) by man are causing an effect which the earth cannot correct for on its own, and without any other than very minor changes outside the normal shifts in temperature, atmospheric makeup, and such.
Hope that the sensors all stay where they are supposed to be, functioning normally, despite the normal (and drastically adverse to such a system) changes in weather around the globe.
Of course, you could use sensors in space, on the ground, and floating on balloons to do the same…to an extent.
But it wouldn’t be anywhere near as accurate…
Thoughts on my idea?