Those who talk about carbon dioxide affecting temperature ignore the fact that water's potential to affect air temperature is well established in science. Water vapor is the only atmospheric gas that can hold or "trap" heat. Those who spend much time in greenhouses know that they are often very humid places because water evaporates from plants and from surfaces that get wet when the plants are watered. Meteorologists typically refer to the water vapor content of the air as relative humidity which is how close the air is to holding as much water vapor as it can hold at its...