Energy from the Sun that makes its way to Earth can have trouble finding its way back out to space. The greenhouse effect causes some of this energy to be waylaid in the atmosphere, absorbed and released by greenhouse gases.
Without the greenhouse effect, earth's temperature would be below freezing. It is, in part, a natural process. However, Earth’s greenhouse effect is getting stronger as we add greenhouse gases to the atmosphere. That is warming the climate of our planet.
How Does It Work?
Solar energy absorbed at Earth’s surface is radiated back into the atmosphere heat. As the heat makes its way through the atmosphere and back out to space, greenhouse gases absorb much of it. Why do greenhouse gases absorb heat? Greenhouse gases are more complex than other gas molecules in the atmosphere, with a structure that can absorb heat. They radiate the heat back to the Earth's surface, to another greenhouse gas molecule, or out to space.
Greenhouse Gases
There are several different types of greenhouse gases. The major ones are carbon dioxide, water vapor, methane, and nitrous oxide. These gas molecules all are made of three or more atoms. The atoms are held together loosely enough that they Eventually, the vibrating molecules release the radiation, which will likely be absorbed by another greenhouse gas molecule. This process keeps heat near the Earth’s surface.
Most of the gas in the atmosphere is nitrogen and oxygen – both of which are molecules made of two atoms. The atoms in these molecules are bound together tightly and unable to vibrate, so they cannot absorb heat and contribute to the greenhouse effect.
A Couple of Common Greenhouse Gases
- Carbon dioxide: Made of one carbon atom and two oxygen atoms, carbon dioxide molecules make up a small fraction of the atmosphere, but have a large effect on climate. There was about 270 parts per million volume (ppmv) of carbon dioxide in the atmosphere in the mid-19th Century at the start of the Industrial Revolution. The amount is growing as burning fossil fuels releases carbon dioxide into the atmosphere. There is about 400 parts per million volume (ppmv) now.
- Methane: A powerful greenhouse gas, able to absorb far more heat than carbon dioxide, methane is made of one carbon and four hydrogen atoms. It is found in very small quantities in the atmosphere but is able to make a big impact on warming. Methane gas is also used as a fuel. When burned, it releases carbon dioxide greenhouse gas into the atmosphere.
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