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In order to do this research, we have to have some way to provide the plants with extra carbon dioxide. We want to create atmospheres that are like the atmospheres of the future, the atmospheres of say 2050.
To do this experiment with elevated CO2 in natural environments, you have to have to do something to contain the CO2, because CO2 disperses very quickly. So we built these chambers. These are clear. The sunlight can get through. The air is introduced at the bottom, and in that air we inject pure carbon dioxide to raise up the co2 inside the chambers near to where we want it to be.
They're like little greenhouses, except that they're open at the top. Opening the top means that the temperature inside is not going to be very different from outside, it will be a little different, that the rain can come in and that the full sunlight can come down on the plants.
But some of these chambers get extra carbon dioxide, and some of them, like this one here, only see what we call present normal ambient CO2. And then we have places that have no chamber at all, like over there, where we do all of our studies in the absence of a chamber and in the absence of the high cO2. Now that's the design of the experiment, we have to do that in order to control for the effects of the chamber on the experiment.
But introducing the air stream at the bottom of the chamber allows us to jack up the carbon dioxide to a level where we expect it to be say at the end of this century, maybe sometime between 2050 and 2075.