Evaporation is the cooling mechanism for land and for our bodies. When the land dries up the temperatures increases warmer and warmer, bringing more heat to the land than with water vapor. 2012 drought is a strong example of this.
As we add more co2 to the atmosphere from around the world, the entire earth holds in more energy directing part of this back to the earth's surface. This is why it is called global warming. Adding more ghg's to the atmosphere is the equivalent to turning the thermostat up on the earth.