What are some of the ways living things use heat? What happens in climates that are very hot? What happens to the oceans and other bodies of water when it becomes hot? What happens when there is an increased amount of water vapor in the atmosphere? How could increased temperatures affect exchange cycles?

What Are Greenhouse Gases?

Greenhouse gases trap heat and energy from the sun and earth in the atmosphere and prevent heat energy from leaving the atmosphere. These gases play a vital role in the atmosphere. They prevent the earth from losing the energy (and water) necessary for life. Without these gases, life would not be possible on earth, because it would be too cold, and there would not be a constant source of energy for life-giving reactions to occur. Sounds confusing. May it helps to realize that too much of a good thing (greenhouse gases) can be a bad thing.

Computer-enhanced picture of the barren surface of Mars, as photographed from the Viking Lander (source: NASA). Mars once had water and an atmosphere of gases, but it all evaporated away into space.

Some greenhouse gases are:

1. Water vapor (exchanges with earth's surface water)
2. Carbon Dioxide (comes from respiration in animals and combustion)
3. Methane (comes from dead living matter and microbes)
4. Ozone (naturally created in the atmosphere)
5. Flouro-carbon molecules (comes from air conditioners and certain industrial processes)

The Ozone Hole

The earth is wrapped in a blanket of ozone, 10 to 40 km above the earth, that helps shield the Earth from UV radiation and excessive heat from the sun. UV radiation can kill bacteria and cause cancer in animals and plants. Ozone is a molecule with three atoms of oxygen, instead of the two molecules in the oxygen gas that we breathe. Sunlight creates this ozone layer by reacting with regular oxygen gas. This reaction runs in both directions, so that some ozone is converted back to regular oxygen (O₂), and there is a hole in the ozone layer over Antarctica. Human activities can affect the ozone layer. For example, release of fluorocarbons and methane into the atmosphere help to destroy ozone.

Antarctic Ozone Levels in Fall 2000 Currently, there is an ozone depleted area over Antarctica that is of great concern to many scientists. The ozone hole is represented by the purple, red, burgundy, and gray areas that appeared over Antarctica in the fall of 2000. The ozone hole is defined as the area having less than 220 Dobson units (DU) of ozone in the overhead column (i.e., between the ground and space). Click here for more on the ozone hole. Source: NOAA TOVS satellite and EPA