Because clouds tops are bright white, they are very good at reflecting solar radiation away from the surface. The more clouds in the sky, the more reflection takes place. F actors in the atmosphere can cause variations in the amount of radiation reaches the surface. That's right, clouds can cause the climate to change. Climatologists are just beginning to understand how, but they think it can be quite substantial.
Clouds are part of what is known as a feedback mechanism.
That is, the warmer the air temperatures get, the more water the air can hold, and thus more clouds can occur. More clouds means more reflection of solar energy into space and therefore less energy for evaporation, means fewer clouds. What can change the climate though, is when uneven heating and cooling causes more or fewer clouds in some areas but not others. I n spite of what some people say, humans do cause climates to change. They do so by altering the ground.