Higher levels of Carbon Dioxide cause trees to lose less water to the atmosphere.
An interesting speculation: More CO2 also causes trees to emit less isoprene, resulting in less smog!
Therefore CO2 emmisions are good for us!
Therefore CO2 emmisions are good for us! If nothing else, the C02 makes trees and other plants grow more vigorously. It's what they convert, along with water and sunlight, to carbohydrates, producing the nasty poisonous (for the plants) byproduct of oxygen.