All that can be seen in this photograph is cloud stretching
several hundred kilometers to the limb of the Earth, yet it tells
us a great deal about the water in the Bering Sea below. The line
or cloud margin running diagonally across the frame with dense,
thick cloud to the right and lighter, more broken cloud to the
left reflects an ocean current margin. A difference in water temperature
on either side of the margin is reflected in the cloud forms condensing
above. This striking cloud boundary stretches for 800-960 kilometers
(500-600 miles) in this photograph. (Courtesy LPI/NASA)
Shuttle astronauts are clearly fascinated by the topside view
of Earth's atmospheric patterns that space flight provides, since
every space shuttle crew takes a significant number of photographs
of clouds. In the past two years, interest in clouds has increased
considerably as scientists attempt to understand global warming
and the greenhouse effect. Efforts to predict climatic changes
associated with global warming have focused new attention on the
warming and cooling properties of clouds. The picture is a complex
one, involving competing feedback mechanisms, and is not fully
understood at this time. All clouds block some fraction of the
incoming solar radiation, and absorb some fraction of the heat
radiated back from the Earth's surface, and the balance between
these two processes is hard to quantify. However, contemporary
thinking suggests that the lower altitude cumulus clouds (such
as pictures Thunderstorms, Brazil and Cumulus Cloud Tops) have
a net cooling effect on Earth's surface, reflecting heat back
to space. Conversely, the higher, thin cirrus clouds (such as
pictures Jet Stream Cirrus and Jet Stream Cirrus, Saudi Arabia)
trap heat, reflecting it back to the surface of Earth.
Current data suggest that the cooling effects of great masses
of cumulus storm clouds over the ocean at mid latitudes outweigh
the heating effects of the upper-level cirrus clouds when considered
on a global scale. Nevertheless, there is cause for concern because
many models of global warming predict a decline in heavy mid-latitude
cumulus storm clouds in the future. The amount of high-level cirrus
cloud is predicted to rise as the cumulus decreases. If environmental
and climatic changes result in altered weather and atmospheric
patterns that adhere to these models, such changes will in turn
induce accelerated global warming.