Greenhouse Gases

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3.3  Greenhouse Gases

3.3a  Greenhouse Gases

Greenhouse gases are gases that absorb energy emitted from the earth and radiate it back into the atmosphere.  If there are too many greenhouse gases, the earth could become too warm. If greenhouse gases dramatically decrease, the earth may be too cool for human activities, such as farming, planting, and harvesting, to occur.


3.3b  Ozone

Ozone isn’t a typical greenhouse gas.  It has two distinct functions in the atmosphere.  High in the stratosphere, it absorbs ultraviolet light from the sun and protects the earth.  Near the ground, it serves as a pollutant and contributor to smog and also has greenhouse characteristics.


3.3c  Nitrous Oxide

Nitrous oxide is the third most influential greenhouse gas.  It stays in the atmosphere for an estimated 115 years, so the 40% contribution from human activities adds up quickly.  The human contribution comes from sources like fertilizer and livestock and human and animal wastes.


3.3d  Carbon Dioxide

Carbon dioxide is an abundant greenhouse gas that is believed to be the main cause of global warming.  The concentration is increasing fairly rapidly.  Carbon dioxide is a natural byproduct of animal and plant respiration but is also caused by human activities like fossil fuel burning, deforestation, and biomass burning.


3.3e  Aerosols

Aerosols are small particles in the atmosphere that often cause cooling by reducing incoming sunlight.  Certain types can cause warming, and all of them change the way clouds behave.


3.3f  Methane

Methane is second only to carbon dioxide in its impact as a greenhouse gas.  It comes from landfills, livestock, natural gas systems, wetlands, and natural gas stores within the earth.


3.3g  Water Vapor

Water Vapor is always in the atmosphere, and it absorbs heat from the sun.  Some amount of water vapor is necessary in the atmosphere. Without it, it would never rain and we wouldn’t be able to go outside without dehydrating very quickly. The amount of water vapor in the air has impacts on humidity, cloud formation, and precipitation.


3.3h  Halocarbons

Halocarbons are the substances responsible for the hole in the ozone layer.  Though they have been heavily regulated, they are still responsible for some amount of global warming.


3.3i  Ozone Layer

The ozone layer is a region in the Stratosphere where ozone is highly concentrated.


3.4  Global Warming vs. Climate Change

"Global warming" describes an average temperature increase of the Earth over time.  "Climate change" describes how weather patterns will be affected around the globe.  These changes could be manifested in changes in climate averages as well as changes in extremes of temperatures and precipitation.  It is likely that the changes will vary depending on what region you are in.  "Global change" describes other effects that don’t fall into either category, like socioeconomic and ecological impacts.


3.5  Models

Atmospheric models are used for every day weather events and short-term forecasting while climate models are used for longer term forecasts.  Climate forecasts are generally divided into statistical forecasts, which cover seasonal to annual forecasts, and global climate models, which use equations to simulate the climate across the entire globe over a long time period.