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What Is The "Greenhouse Effect"?

The greenhouse effect refers to heat from the sun trapped in the atmosphere by gases such as water vapor and carbon dioxide (CO₂), much like trapped heat from the sun warms the interior of a greenhouse, says Richard Nelson, K-State Extension energy specialist. In proper balance, the greenhouse effect is beneficial to life on earth.

“This trapping of the sun's heat allows for a hospitable living environment with a fairly constant average temperature. Without this naturally occurring greenhouse effect, temperatures on earth would be significantly colder than they are, and we would not be able to survive,” Nelson explains.

But when the greenhouse effect becomes too intense, temperatures on earth may get uncomfortably warm. This is popularly known as “global warming.”

Global warming is an increase in the earth's temperature caused by increased greenhouse gas emissions. Since the last ice age, the temperature of the earth has been pretty stable. However, recent emissions of greenhouse gases such as CO₂ have caused a gradual increase in the earth's temperature. This increased release of CO₂ traps more of the sun's heat in the atmosphere. Greenhouse gases are being emitted more quickly than they can be absorbed in the earth's forests, prairies, and oceans.

Scientists generally agree on the continued likely rise in average global temperatures over the next century. There are four primary greenhouse gases: water vapor, carbon dioxide, methane, and nitrogen oxide, with water vapor being the most common greenhouse gas. Carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) result primarily from human-induced activities. CO₂ is released to the atmosphere primarily due to the combustion of fossil fuels such as coal, gasoline, diesel fuel, and natural gas, and is also produced when solid wastes and wood and wood products are burned.

All greenhouse gases contribute to trapping heat in the atmosphere, but some are more effective than others, which is reflected in their global warming potential (GWP), Nelson says.

“The GWP simply compares the heat-trapping ability of carbon dioxide, methane, nitrous oxide, and other greenhouse gases to carbon dioxide. Carbon dioxide was chosen as the baseline greenhouse gas and assigned a value of 1. Methane and nitrous oxide are 21 and 310 times more effective than CO₂, respectively. Therefore, for every ton of CH₄ or N₂O, the GWP in terms of carbon is 21 and 310 times the amount emitted, respectively. These values are referred to as the carbon equivalent,” Nelson explains.

Several potential adverse effects are related to global warming. "With an increase in the earth's temperature, moisture will evaporate more quickly causing some areas to be more arid and others to have increased rainfall,” Nelson says. “The continued addition of greenhouse gases to the atmosphere could possibly raise the earth's average temperature by several degrees in the next century, which could have dramatic effects on polar melting, changing shorelines, and changing agricultural production patterns.”

Most of the United States is expected to warm, although scientists have been unable to accurately determine which parts of the United States will become wetter or drier, he adds.

For more information, contact:
Dr. Richard Nelson  
Extension Engineering 
Kansas State University
Manhattan, KS 66506
(785) 532-4999
rnelson@ksu.edu 

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