I'm sure it was measured, and they should have explicitly said what it was. It seems that they probably fed it 7% which is higher than the atmosphere in density, but only equivalent to only about 500 feet in altitude. So it's not all that much for the purposes they were after - a demo.however on the screen shot shown in the video you can see 7%. That's why I asked. And it is why those who have viewed the video from the skeptics viewpoint, make the statement they make. It is what is showing. One can summize that they are feeding many times the CO2 than the atmosphere would ever see. But one won't ever know because the CO2 wasn't measured to show what the PPM actually was. Seems sort of simple thing to do, yet avoided.
The Myth busters brought in measuring devices for some reason. CO2 was being measured somewhere and it was decreasing. Luke what would happen in a non airtight box after it received a bolus of additional CO2. There wasn't any mention of constructing controls with no CO2 therefore I think we can assume the control was at standard CO2 concentration and the CO2 box was increased, apparently in the vicinity of 200 times.
Using CO2 which has been doubled at least seven times to get 1C increase doesn't leave me impressed actually.