The temperature difference between the Tropics and the Poles creates winds and ocean currents that carry excess heat and moisture. When the moisture encounters cooler temp- eratures as it moves to the poles, clouds form and reduce the emission of energy to space. Clouds play a complex role in the Earth's radiation budget. Low Clouds reflect much of the sunlight that falls on them, but have little Effect on the emitted energy. Thus, low clouds act to cool the Current climate.
High clouds reflect less energy, but trap more of The energy emitted by the surface.
However, the measurements could not tell us why the clouds in different parts of the Earth were different from one another. This chart illustrates our current understanding of the relative importance of these various kinds of climate forcing mechanisms. The uncertainty in what clouds will do in the future remains the largest source of uncertainty in predicting the future climate. About 500 schools are Currently participating in this international program.