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Sun, Air and Life.  
Every layer of gases with its different energy transformations plays a role in the global energy balance that enables life as we know it.

Teaching Climate Change home page

Sun                                              Energy from the sun (solar energy) travels in invisible waves.* 

*From a distance the sea looks flat and the waves of energy traveling through it are invisible. The waves of solar energy are so tiny we can never magnify them or get “close enough” to see them.

Some waves contain lots of energy and can damage living things when they strike them. This is the symbol for these high frequency waves.  An example is ultra violet light (invisible to our eyes).

This is the symbol for low frequency waves i.e. ones containing less energy. An example is infrared radiation (invisible to our eyes but we feel it as heat.)

Air
A bit like particles in water, gases of different sizes and weights tend to be found in different levels of the atmosphere. Only the smaller, lighter molecules of gases like oxygen and nitrogen tend to exist above 80 kilometers. Larger, heavier ones like water vapour and carbon dioxide are concentrated at the lower levels.

Fortunately the small molecules of gas high in the atmosphere can absorb the potentially damaging high frequency waves and transform them into heat. As a result most of the very high frequency waves do not reach Earth’s surface. These molecules in the Thermosphere make only a small contribution to the total thermal energy retained by the atmosphere as they are small and far apart.

90% of ozone is found in a relatively narrow band lower down. Ozone absorbs less high frequency waves –the ultra violet waves that still contain enough energy to damage us. History has shown human activities can have a major impact on this layer.

The gas molecules of the atmosphere do not absorb the less high frequency waves that form visible sunlight and these waves pass right past them to the Earth’s surface. There solar energy is transformed into infrared radiation i.e. low frequency waves.

The large gas molecules like water, carbon dioxide, methane etc can absorb low frequency waves and retain the thermal energy.

As a result the atmosphere close to Earths surface averages a comfortable 15°C.

Life                                 
All these energy transformations at every level combine in this wonderful way to work to provide the protection and the thermal balance that enables life on Earth.

*****Language Alert. ******

Life exists on Earth because the planet is subject to constant global warming by the sun. In this extraordinary, wonderful and dynamic process the constant inflow of solar energy is in balance with the outflow of thermal energy.
Some people have a different and confusing use for the term. They use it to describe the potentially risky process in which human activities may be altering this balance and increasing the amount of thermal energy retained in the atmosphere. A helpful term for this process is Thermal Energy Build-Up. This term does not imply all regions will experience warmer temperatures and the dynamic nature of normal global warming remains clear.

  This page is part of a programme  Communicating and Teaching the scientific principles underlying Climate Change issues.\

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Transformation of high frequency solar energy into heat (low frequency infrared radiation).   
Not shown is:
Sunlight reflected back to space without being transformed.
Low frequency (infrared radiation) absorbed direct from the sun.
Circles represent molecules. 
Note: Nothing is to scale

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Web data Radiation & the  Atmosphere









Web lesson Radiation in the Atmosphere

Web Illustration of Global
Energy
Balance
**Be Language Alert**