This is completely pointless. No one questions the greenhouse effect (it is used to grow food all over the world). The question is whether or not additional CO2

This is completely pointless. No one questions the greenhouse effect (it is used to grow food all over the world). The question is whether or not additional CO2 that was put in the atmosphere by human activity over the last ~100 years is the primary cause of the ~1°C average surface temp increase in that time period. An experiment for children isn't going o add anything of value here. Labor or in this case kitchen experiment do not model the real wold. And Correlation does not imply causation. And finally when you establish a correlation, it does not have to be linear i.e. more of X does not mean it must case more of Y. Complex systems that are in some kind of balance often produce their own counter effect to change. This is the primary reason why such a stable balance could even form over long periods of time. The self correction properties of the whole system is very much a requirement for the balance to exists in a complex system like the climate.