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Properties of Greenhouse Gas

The Earth's atmosphere is made up mostly of nitrogen (78%) and oxygen (21%), with a slight amount of trace gases (1%). Trace gases that trap heat in the atmosphere are called greenhouse gases. Although small, the percentage of greenhouse gases in the atmosphere contributes immensely to changes in climate. Below is a list of the major greenhouse gases that enter the atmosphere, primarily due to human activities.

  1. Carbon Dioxide

    • Carbon dioxide is an odorless, colorless gas that is faintly acidic and non-flammable. Although carbon dioxide occurs naturally in the atmosphere, human interference with the carbon cycle (primarily through deforestation and the burning of fossil fuels) has artificially increased atmospheric concentrations of carbon dioxide dramatically since the industrial revolution began in the 1700s. As of 2011, the level of carbon dioxide in the atmosphere has risen more than 30 percent since pre-industrial times. Due to its atmospheric abundance, carbon dioxide contributes the most of all the greenhouse gases to global warming.

    Methane

    • Methane is a principal component of natural gas. It is colorless and odorless yet highly flammable. Methane is emitted from sources both natural (such as swamps and fossil fuel beds) and human-influenced. In the United States, the largest human-influenced methane emissions come from landfills, domesticated livestock and fossil fuel extraction. Methane's chemical lifetime in the atmosphere is relatively short at nine to 15 years. However, methane is about 21 times more powerful at warming the atmosphere than carbon dioxide, making it a near-term threat to global temperatures.

    Nitrous Oxide

    • Nitrous oxide is a colorless gas with a faintly sweet odor. It occurs naturally, but it is believed that 40 percent of the atmosphere's current level has been caused by human activity, such as the use of fertilizers and fossil fuel combustion. Although not nearly as prevalent in the atmosphere as carbon dioxide, nitrous oxide has heat-trapping effects, which are approximately 310 times more powerful than carbon dioxide as well as a long atmospheric lifetime of about 120 years.

    Fluorinated Gases

    • Although they make up a relatively small portion of the atmosphere, fluorinated gases are also known as high global warming potential (high GWP) gases for their potency in regards to impact on the Earth's climate. Fluorinated gases are all human-made. Some, like perfluorocarbons (PFCs), can be the synthetic byproducts of industrial processes such as aluminum smelting. Others such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs) were once widely used in refrigeration and air conditioning but are now being phased out because of global regulation.

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