What is Climate Change?

Greenhouse Gases

Most greenhouse gases occur naturally. However modern industry and lifesyles have led to new sources of greenhouse gases, as well as to the emission of entirely new greenhouse gases. Among the most important greenhouse gases are:

Water Vapour

Water vapour come from natural respiration, transpiration, and evaporation. The amount of water vapour stored in the atmosphere increases as the Earth's surface temperature rises.

Carbon dioxide (CO₂)

Carbon dioxide comes from the decay of materials, respiration of plant and animal life and the natural and human-induced combustion of materials and fuels. It is removed from the atmosphere through photosynthesis and ocean absorption.

Figure 1: Trends in CO2 Concentrations (Past 1000 years)

Methane (CH₄)

Although there is less methane than carbon dioxide in the atmosphere, methane is a more effective heat-trapping gas. It comes from the decay of matter without the presence of oxygen. Primary sources include wetlands, rice paddies, animal digestive processes, fossil fuel extraction, and decaying garbage.

Nitrous oxide (N₂O)

Soils and oceans are the primary natural source of nitrous oxide. Humans contribute through soil cultivation and use of nitrogen fertilizers, nylon production, and the burning of organic material and fossil fuels

Ozone (O₃)

Ozone exists naturally in the lower atmosphere in minute quantities. It also can be produced in the lower atmosphere from a reaction invovling several human-produced pollutants and sunlight.

Halocarbons

Halocarbons are human-produced chemical compounds containing members of the halogen family (bromine, chlorine, and fluorine) and carbon. They are some of the most effective heat trapping greenhouse gases of all. Halocarbons are typically involved in various industrial and home uses with chlorofluorocarbons (CFCs) being the most familiar.

See the following:

• Greenhouse Gases (GHG)
• The Greenhouse Gas Emissions Outlook to 2020

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