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1) Give information on the main source (naturally occurring/man made) of a selected gas.

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1) Give information on the main source (naturally occurring/man made) of a selected gas.

Global warming, for almost a century, has been a very controversial issue. Scientists, determined to prove once and for all that man made sources are the main cause for global warming, have been surmounting more and more evidence to support this. The noticeable increase of late in the average temperature of our Earth has raised concerns. These concerns are regarding exactly what chemicals we should we using in our day to day lives. How are these chemicals, in the form of gases, causing global warming? Are they really enhancing the greenhouse effect? If so, how we can lessen the production and release of these harmful chemicals into our atmosphere? All these questions will be brushed over in this assignment.

There are quite a few chemicals that are considered influential in the greenhouse effect. These chemicals (which are all gaseous) include CO2 (carbon dioxide), CH4 (methane), N2O (nitrous oxide), Halocarbons (mainly chlorofluorocarbons or CFCs), and O3 (ozone).

The following table shows the sources of these gases and their relative effectiveness at trapping heat relative to CO2. CO2 is mainly responsible for the natural greenhouse effect, although events such as deforestation may now be pushing CO2 levels higher than normal.


Main Source

Heat trapping effectiveness compared with CO2

Overall Contribution to increased global warming

Life Span in the Atmosphere (years)


Combustion of fossil fuels and biomass





Anaerobic decay of organic matter caused by intensive farming





Artificial fertilizers and combustion of biomass





Secondary pollutant in photochemical smogs





Refrigerant, propellant, foaming agents, solvent

10000 - 25000



...read more.


The graph below shows the amount of CFC-11 in the atmosphere, measured in ppt (parts per trillion) and measured from various sites around the world over a period of time. As it can be seen, the amount of CFC-11 has jumped up tremendously from 1977 to 1990, where there was awareness for the dangers of CFC. This awareness unfortunately did not help stem the flow of CFC production. Obviously, the plateau of the amount of CFCs during the 1990s shows that there were steps taken to slow down the production of CFCs. In fact, the world’s goal is to stop producing these chemicals altogether.


CFCs have many uses, and seem to make a great contribution to our society. But why do they seem to be a problem? They are not a problem down on the ground. They are essentially harmless substances, and are not a threat at all to humans directly. Even in our lower atmosphere, they are inert. But, when they reach the upper atmosphere, the events that take place there are what scientists are worried about. At this height, CFCs essentially play two roles in enhancing the greenhouse effect.

Firstly, CFCs physically trap heat extremely proficiently. Even at lower altitudes in the atmosphere, CFCs would collectively provide their own blanket over the Earth, which would in turn help to heat the planet up.

Secondly, CFCs chemically provide a hazard to our atmosphere.

...read more.


 [Internet]. Michael Pidwirny. Department of Geography, Okanagan University College.

Available:        http://www.physicalgeography.net/fundamentals/7h.html

[Accessed 11 Feburary 2005].

Neuss, G. 2001. Chemistry for the IB Diploma. Oxford: Oxford University Press.

Anon. n.d. Activity 2 – Global Warming. [Internet].

Available:        http://community.middlebury.edu/~rosenber/DR-personal-homepage/globalwarming/gwact2.html

[Accessed 11 Feburary 2005].

Elkins, J. 1996. Chlorofluorocarbons (CFCs). [Internet]. David E. Alexander and Rhodes W. Fairbridge. Kluwer Academic, Boston.

Available:         http://www.cmdl.noaa.gov/noah/publictn/elkins/cfcs.html

[Accessed 11 Feburary 2005].

Anon. 1999. CFCs and the Atmosphere. [Internet]. The National Asthma Council Australia. Melbourne.

Available:        http://www.nationalasthma.org.au/resources/cfc/cfcozone.html


[Accessed 11 Feburary 2005].

Anon. n.d. Ozone Depleting Substances. [Internet]. Environment ACT. ACT.

Available:        http://www.environment.act.gov.au/corporate/contactus.html

[Accessed 11 Feburary 2005].

Xavier Tung. n.d. Chlorofluorocarbons. [Internet]. SKH Tsang Shiu Tim Secondary School. Hong Kong.

Available:        http://hk.geocities.com/xavier114fch/02/02i.htm

[Accessed 11 Feburary 2005].

Anon. n.d. Ozone. [Internet]. www.studyworld.com. Unknown Address.




[Accessed 11 Feburary 2005].

Anon. n.d. The Ozone Hole: Ozone Destruction. [Internet]. The Ozone Hole Inc. Pennsylvania.

Available:         http://www.theozonehole.com/ozonedestruction.htm

[Accessed 11 Feburary 2005].

U.S Environmental Protection Agency. n.d. Ozone Science: The Facts Behind the Phaseout. [Internet]. EPA. Washington, D.C.

Available:         http://www.epa.gov/docs/ozone/science/sc_fact.html

[Accessed 11 Feburary 2005].

Anon. n.d. The Vienna Convention and the Montreal Protocol. [Internet]. United Nation Development Programme. New York.

Available:         http://www.undp.org/seed/eap/montreal/montreal.htm

[Accessed 11 Feburary 2005].

...read more.

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