From Ecopedia

Overview

Greenhouse Gases are chemical compounds found in the atmosphere of the earth, occurring either naturally or produced as a result of human-induced industrial processes.

Some of the naturally and most-abundantly found GHGs, in order, include:

• Water vapor

• Carbon dioxide (CO2)

• Methane (CH4)

• Nitrous oxide (N2O)

• Ozone

• Chlorofluorocarbons (CFCs)

Other industrially-produced GHGs consist of:

• sulfur hexafluoride(SF6)

• hydrofluorocarbons (HFCs)

• perfluorocarbons(PFCs)

Environmental Information

Greenhouse effect

Greenhouse gases freely permit sunlight through the atmosphere. After striking the surface of the earth, some of the sun’s radiation is re-radiated back into space in the form of heat as infrared radiation.

Greenhouse gases, after absorbing the infrared radiation, trap the generated heat making the earth’s atmosphere warmer by about 33°Celsius, producing the Greenhouse effect. In 1824, Joseph Fourier discovered the greenhouse effect phenomenon. Physical processes such as anthropogenic or enhanced human activities significantly contribute to the greenhouse effect.

The Greenhouse effect is the major contributing factor for global warming. If the current trend of increased GHG production continues, severe climate changes such as severe droughts, floods, rising sea levels, altered rainfall patterns are bound to occur.

As per IPCC estimates, over the past hundred years, earth’s climate warmed up between 1.1° -1.6°F due to increased GHG concentrations and anthropogenic activity found to be the crucial contributing factor.

Contributions to Greenhouse Gases

Human activities are found to significantly increase the levels of naturally-occurring GHGs including carbon dioxide, nitrous oxide and methane.

Intergovernmental Panel on Climate Change (IPCC) observed that most of the increase in global temperatures since mid-twentieth century is mainly due to increased anthropogenic (human-induced) GHG concentrations.

For example, massive amounts of carbon dioxide are getting released into the earth's atmosphere due to excessive burning of fossil fuels (natural gas, oil and coal) as well as solid waste, wood and wood products that are found in landfills. Anthropogenic activities over long periods of time are found to contribute significantly to the increase in atmospheric CO2 levels.

Cement production, combustion and deforestation are some of the major causes for increased CO2 levels. Environmentalists observed that CO2 contribution to the greenhouse effect is between 9-26%.

Additionally, Emissions of Nitrous oxide are due to various industrial as well as agricultural processes or during combustion of fossil fuels or solid waste.

Methane emissions might occur during organic waste decomposition either in landfills, livestock farming or during fossil fuel production and transport. Methane emissions are found to contribute 4-9% to the greenhouse effect.

Other gases such as ozone and water vapor contribute 3-7% and 36-70% respectively, to the greenhouse effect.

Measures for Reducing GHG Emissions

Many countries across the world started adopting stringent measures to reduce emissions of greenhouse gases and switch to eco-friendly renewable energies such as wind power and solar power.

In an attempt to develop international strategies to combat global changes in climate, European Union became instrumental in putting forth two major UN (United Nations) treaties for reducing

GHG emissions:

• UN Framework Convention on Climate Change (UNFCCC) agreed in 1992

• Kyoto Protocol, agreement signed in 1997

UNFCCC

The members of the convention signed Copenhagen Accord, which obliged several developing as well as developed countries to commit to minimizing carbon emissions and pledging support for transfer of technologies, besides acknowledging the crucial role of forest systems in countering the affects of climate change.

Kyoto Protocol

The international agreement signed in Kyoto Protocol, committed the member countries to set binding targets for minimizing greenhouse gas emissions by about 5% against the levels recorded in 1990. The protocol set a time period of five years, from 2008 to 2012, to achieve the target level. The rules set for the implementation of the protocol, known as “Marrakesh Accords”, were finalized and adopted at COP7 in the year 2001, in Marrakesh.

While the UNFCCC encouraged industrialized nations to stabilize greenhouse gas emissions, the Kyoto Protocol committed the member countries to reduce the emissions.

References

http://en.wikipedia.org/wiki/Greenhouse_gas http://en.wikipedia.org/wiki/Greenhouse_effect http://www.umich.edu/~gs265/society/greenhouse.htm http://environment.about.com/od/faqglobalwarming/f/greengases.htm http://tonto.eia.doe.gov/energyexplained/index.cfm?page=environment_about_ghg http://tonto.eia.doe.gov/energyexplained/index.cfm?page=environment_how_ghg_affect_climate http://unfccc.int/kyoto_protocol/items/2830.php http://unfccc.int/essential_background/items/2877.php