An AGW experiment

I'm going to show my technical ignorance here, but bear with me.

The AGW fanatics contend that a system as complex and fluid as the earth's climate can affected negatively by the increase in one substance (CO2). I propose a simple experiment.

Take 3 clear, strong boxes that can withstand a complete vacuum (at least for a few minutes). The size of the boxes is flexible, but I'd say a cube at least a yd (ok, a metre!). Provision must be made so that all three boxes can be put outside and receive the same amount of sunlight. What we're building is three identical greenhouses.

Now, pull a vacuum on each of the boxes, refilling them with, respectively, with the same amounts of: 1-normal atmosphere (air) 2-atmosphere with double the normal % of CO2 3-atmosphere with triple the normal % of CO2.

Leave in the sun for a year, monitoring the temperature with the most accurate instruments available.

I'll bet that there's no discernable difference in temp between the boxes.

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