Greenhouse Gases And Consequences Essay Research Paper

Greenhouse Gases And Consequences Essay, Research Paper

Greenhouse Effect

The greenhouse effect is a natural phenomenon that warms the earth and enables it to support life. Without it, the average temperature on earth would be around -18 degrees C, instead of the current +15 degrees C – a frozen wilderness. It works on the same principles as the ordinary glass garden greenhouse, where glass allows light to get in, but does not allow for the heat to get out. This makes for a much higher temperature inside the greenhouse.

On a planetary scale, similar processes occur. Light from the sun has no trouble penetrating the atmosphere and reaching the earth’s surface, warming it. The earth re-radiates much of this heat in the form of (invisible) infrared radiation. Infrared rays have a longer wavelength than visible light, and for this reason can be absorbed by certain gases in the atmosphere, labelled greenhouse gases. This absorption of heat warms up the atmosphere, which in turn radiates some of the heat back to the earth.

Greenhouse gases include water vapour, carbon dioxide (CO2), methane (CH4), chloroflurocarbons (CFCs), Ozone (O3), and Nitrous Oxide (N2O).

It all seems very straightforward: greenhouse gases trap the sun’s heat, warming the planet sufficiently for life to exist. There is, however, one problem: human activity has dramatically increased the amount of greenhouse gases in the atmosphere.

Over the last two centuries the concentration of greenhouse gases in the atmosphere has increased quite significantly, mainly as a result of burning fossil fuels for industrial purposes. For example, atmospheric concentrations of carbon dioxide have increased from 280-285 parts per million in 1800 to 350 parts per million today. Currently the concentration of CO2 is rising by 0.4% per year. Methane has increased from about 750 parts per billion to 1700 parts per billion over the past 200 years, and nitrous oxide appears to be increasing at a rate of about 0.3% per year.

As the various greenhouse gases accumulate in the atmosphere, the amount of infrared radiation that is trapped increases. It is estimated that if we continue at our current rate of CO2 emissions alone, the average global temperature will rise by 1.5 to 4.5*C over the next 40 to 50 years.

Although the most important cause, burning of fossil fuels is not the only cause of the build-up of greenhouse gases in the atmosphere. Other causes include deforestation (trees absorb carbon dioxide, turning it into oxygen), the use of fertiliser (a source of N2O), and rotting organic matters (which produce methane).

Because of the many factors involved in the process, it is extremely difficult to accurately forecast the effects of an average global temperature rise of, say, 3 degrees on the earth in general or on Australia in particular. It is, however, possible to make some points with a reasonable degree of certainty.

The sea level would rise anywhere between 30 and 150 cm. This is the result of two factors: a partial melting of the Antarctic and Greenland icecaps, and an expansion of ocean water. It seems obvious that a global rise in temperatures would gradually melt these two big icecaps, producing an increase in sealevels. This is, however, a very slow process that will probably take hundreds of years.

The second factor, expansion of ocean water, will take place in decades rather than centuries. It refers to the fact that heated matter expands: warmer ocean water will expand, producing a rise in sea levels.

Another feature of global warming that seems reasonably certain is that the increase in temperature would not be uniform over the world. Generally, changes at the poles would be greater than at the equator. Cold seasons would shorten, and warm seasons lengthen. Some regions would experience an increase in rainfall, with more damage from flooding and storms. Other regions would become drier.

These changes would have enormous effects on agriculture and food supply, as well as the supply of drinking water and public health.

A third forecast consequence of increased temperatures is an increase in tropical cyclone activity. Northern Australia can expect increases in both the intensity and frequency of cyclones, and also the cyclone region will move up to 400 kilometres further South. It is, however, impossible to make any accurate forecasts on actual changes in risk in any particular region.

The effects of global warming on Western Australia could include a reduction in winter rainfall by up to 20% in areas that derive their rainfall from the Easterly passage of cold fronts, an increase in sea level between 0.2 and 1.4 metres, a decrease in the spread of salinity in low rainfall areas, increased wind speeds in the South, and decreased wind speeds in the North. Also, the duration and intensity of tropical cyclones would increase, and they would affect a greater area. These changes in climate will affect every aspect of our lives. Living in Perth will be more like living in Broome or Port Hedland.

These climate changes are likely to have significant effects on our lifestyles, natural environment, coastal areas, and agriculture:

Agriculture could be affected in a number of ways. Most importantly, the warmer climate and different weather may require changes to agricultural production

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