The study of clouds, where they occur, and their
characteristics, play a key role in the understanding of climate
change. Low, thick clouds primarily reflect solar radiation and
cool the surface of the Earth. High, thin clouds primarily
transmit incoming solar radiation; at the same time, they trap
some of the outgoing infrared radiation emitted by the Earth and
radiate it back downward, thereby warming the surface of the
Earth. Whether a given cloud will heat or cool the surface
depends on several factors, including the cloud's altitude, its
size, and the make-up of the particles that form the cloud. The
balance between the cooling and warming actions of clouds is
very close although, overall, averaging the effects of all the
clouds around the globe, cooling predominates. The Earth's
climate system constantly adjusts in a way that tends toward
maintaining a balance between the energy that reaches the Earth
from the sun and the energy that goes from Earth back out to
space. Scientists refer to this as Earth's