Geoscience Reference
In-Depth Information
Warming and cooling effects
As well as the warming effects of the GHGs, the Earth's climate system is complicated in
that that there are also cooling effects (see
Figure 14
). This includes the amount of particles
in the air (which are called aerosols, many of which come from human pollution such as
sulphur emissions from power stations) and these have a direct effect on the amount of sol-
ar radiation that hitsthe Earth's surface. Aerosols may have significant local or regional im-
pact on temperature. In fact, the AOGCMs have now factored them into the computer sim-
ulations of climate change, and they provide an explanation of why industrial areas of the
planet have not warmed as much as previously predicted. Water vapour is a GHG, but, at
the same time, the upper white surface of clouds reflects solar radiation back into space.
This reflection is called 'albedo'—and clouds and ice have a high albedo, which means that
they reflect large quantities of solar radiation from surfaces on Earth. Increasing aerosols in
the atmosphere also increases the amount of clouds as they provide points on which the
water vapour can nucleate. Predicting what will happen to the amount and types of clouds,
and their warming potential, has been one of the key challenges for climate scientists.
