Table of Contents

RADARSAT-1 Climate Change

A Science Unit for Grades 11 and 12

The Atmospheric Heat Balance

The thermal stability of the Earth's climate is controlled by many complex and interacting feedback loops. It is not known completely how all of these processes interact, although scientists have made considerable progress in sorting out the fundamental mechanisms affecting climate.

For example, it is well known that carbon dioxide (CO₂) plays an important role in helping the Earth stay warm. However a look at the planet Venus gives us reason for considerable concern. In the case of Venus, the CO₂ in its atmosphere appears to have had a positive feedback affect, causing the much feared "runaway greenhouse effect".

Some of the factors which affect the Earth's heat balance are shown in the diagram below.

Features which directly reflect solar energy back into space, such as clouds, tend to cause a general cooling of the Earth's surface, which in turn causes a cooling of the atmosphere.

Some well known gases, such as carbon dioxide, water vapour, and methane reduce the atmosphere's transparency to infrared (thermal) radiation and this tends to trap heat in the Earth's atmosphere making the climate warmer.

There are of course many questions which as yet are still unanswered.

1. Will climate changes occur slowly, with a tendency to "self-correct" in response to various negative feedback mechanisms?

2. Or, will changes occur abruptly and catastrophically due to strong positive feedback mechanisms?

3. Are all climate-modifying factors identified?

4. How do factors affecting climate interact with each other?

5. What are the early warning signs of climate change on a global scale?

It is the investigation of this last question for which RADARSAT is especially well suited!

Further reading