Basics-climate-cange-pg2

Green House Gases

The naturally occurring gases such as water vapour, carbon dioxide, ozone, methane and nitrous oxide trap infrared radiation in the atmosphere and contribute to rise in global temperatures. They are called Green house Gases and this phenomena is called the Greenhouse Effect. Greenhouse gases are essential in maintaining the temperature of the earth; without them the planet would be so cold as to be uninhabitable. Likewise, an excess of greenhouse gases can raise the temperature of the planet to unlivable levels. The term greenhouse gas is applied to, in order of relative abundance: water vapour, carbon dioxide, methane, nitrous oxide, ozone and CFCs.

Greenhouse gases are produced by many natural and industrial processes, which currently result in CO2 levels of 380 ppmv in the atmosphere. Based on ice-core samples and records current levels of CO2 are approximately 100 ppmv higher than during pre-industrial times, when direct human influence was negligible.

Some greenhouse gases such as carbon dioxide are emitted to the atmosphere through natural processes and human activities. Other greenhouse gases (e.g., fluorinated gases) are created and emitted solely through human activities. The principal greenhouse gases that enter the atmosphere because of human activities are:

Carbon Dioxide (CO2): Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement). Carbon dioxide is also removed from the atmosphere (or `sequestered') when it is absorbed by plants as part of the biological carbon cycle.

Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.

Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e., CFCs, HCFCs, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (`High GWP gases').

Climate Change- Green House Gas Emission, 2008 Draft Inventory of Greenhouse Gas Emissions and Sinks, Environmental Protection Agency http://epa.gov/climatechange/emissions/index.html