Has anyone ever looked into the environmental impact of carbonated beverages?
Don't they result in tons of CO2 being released into the atmosphere ?
Depends on how the CO2 is generated. In home-made soda (you can easily make gingerale--some grated ginger, some sugar, water, a pinch of yeast, and a 2-liter bottle is all you need), it's the same as burning wood: the carbon came from the atmosphere anyway, so it's a wash. Basically, as long as they're pulling the CO2 out of the atmosphere and not out of the ground it's irrelevant to these calculations.
The issue isn't the mere addition of CO2 into the atmosphere. It's a question of reservoirs. CO2 in the atmosphere and biosphere generally switches between them fairly easily, and as long as biomass remains roughly stable everything's stable. It's the transfer of CO2 from the lithosphere (fossil fuels and, to a lesser extent, carbonate minerals) to the atmosphere that has any real impact. Which is a major complication in this label scheme: someone, somewhere has to figure out how to deal with the combination of biomass and fossil fuels commonly used (California has 10% ethanol in gas, for example). And every time an institution changes anything the label will have to be updated.