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An Essay Upon Global Warming

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Introduction

20/04/07 Tim Lees 10AM An Essay Upon Global Warming Global Warming is defined by Encyclopaedia Britannica as 'potential increase in average global atmospheric temperatures resulting from the greenhouse effect.' This is, literally speaking, incorrect; literally, Global Warming means 'an increase in average global temperature', which could be for any number of reasons e.g. the sun increasing in size (bringing it closer to the earth and thus increasing the intensity of radiation reaching earth) and/or the sun increasing in temperature (a greater amount of radiation being emitted would result in a greater amount of radiation being received). However, in my opinion as a result of media attention, when we talk of global warming, we are usually talking about the greenhouse effect. The two potential issues mentioned above will almost certainly not become important for around a billion years, yet the greenhouse effect is, according to many scientists, already taking effect. Therefore, for us to be able to talk about global warming, it is important to have an understanding of the greenhouse effect. Electro-Magnetic-Radiation (EMR) is emitted by the sun, and contains light, as well as such things as infrared radiation and ultra-violet radiation. A small fraction of this radiation arrives at the earth's atmosphere, where some of it is absorbed, but in the most part it passes through to the surface of the earth. The molecules that make up the surface reflect much of this, but also absorb some. This increases the frequency of their vibrations; they are heated up. The heat dissipates out into the air around the surface and into the surrounding earth. Some of the energy is radiated back out; largely as infrared radiation because the particles don't get hot enough to emit much light but neither are they cool enough to emit micro or radio waves. ...read more.

Middle

So, is global warming taking place? Models have been produced to simulate the effect that greenhouse gasses will have upon the mean global temperature. The models described by the UN as 'generally accurate' in 1990 predicted that by 2000, the mean surface temperature should have increased by between 1.3 and 2.3�C since the late 19th century, with a higher figure for the northern hemisphere than the southern one. The currently observed warming is considerably lower. By 1995, (yes, it actually took them the best part of five years) the UN noticed that these models weren't so accurate, "unless a lower climate sensitivity is used". Also they said that "There is growing evidence that increases in sulphate aerosols are partially counteracting [the warming due to] increases in greenhouse gases." Sulphate aerosols are emitted when fossil fuels containing sulphur are burned. They are tiny dust particles that reflect away the sun's radiation before it can be absorbed by the surface. This reduces the amount of energy that can reach the surface, and so, even though a greater portion of energy received would be retained, less energy would be received. Because sulphate aerosols are usually produced along with greenhouse gasses, although in lesser amounts, it makes sense that they at least could be, counteracting global warming. So, global warming could be caused by greenhouse gasses, but, because of the sulphate aerosols that are being produced along with them, global warming is at least being slowed, if not halted. Another factor could be forests, which in the Northern hemisphere are believed to be absorbing up to 25% of the total emitted. In some forests, tree growth is abnormally fast, yet in others, tree growth is much slower than before. ...read more.

Conclusion

As the O-Zone hole increases in size, so more UV rays can pass through. This energy has to go somewhere, and I'll wager that the ice sheets are absorbing a fair portion of this radiation, and heating up along with it. A quasi-flaw with this suggestion is that the Southern O-Zone hole is considerably larger than the Northern hole, and the melting is presently worse in the Arctic. However, this is less of an issue than it may at first seem due to the fact that the Antarctic is considerably colder and much of the ice will have a higher melting point due to the reduced percentage in contact with the sea. Or perhaps this is all a load of rubbish and it's just a coincidence that the ice sheets are melting. In the 17th century, we know that people went ice-skating on the Thames. It seems unlikely that there was an unusually small amount of greenhouse gasses during this period, and so perhaps the earth just naturally changes in climate. The Thames hasn't frozen over to an extent that you could go ice-skating on it at all this century, not even during 1940. It is true that the hottest summers since records began were nearly all this decade, but records only began in 1880. Bearing in mind the possible number of combinations for the alignment of the poles on a given day in a year (1,690,052,000), 120 years worth of results is hardly going to help when determining what is going to occur at a time such as the one we are potentially facing; a time of climatic change. We must also bear in mind, however, that we may not be heading toward anything other than usual. ...read more.

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