An Essay Upon Global Warming

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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. Gasses in the atmosphere then absorb the radiation, or it passes through into space. Some gasses are more absorbent than others, just as some materials are opaque whilst others are transparent. In particular, gasses emitted naturally by volcanoes, largely COx, SOx, and NOx, are infrared absorbent but Hydrocarbons such as methane, a major constituent of ‘farts’, are major factors when talking about ‘greenhouse emissions’. Clouds, formed when water vapour condenses in the right conditions, absorb and also reflect large amounts of this radiation. Water evaporates when heated, and in particular the sun evaporates a great deal of water. The water vapour, which is less dense than air, will rise and form clouds. Much of the EMR emitted by the sun can penetrate the earth’s atmosphere because the sun emits a great deal of light, and the atmosphere is fairly transparent at all stages. Some of it cannot get out because it is re-radiated as infrared, which is largely absorbed by the ‘greenhouse gasses’ and the clouds. This is similar to the situation inside a greenhouse, which heats up because energy in the form of light passes through the glass, but cannot get out as much of it is converted into infrared, which the glass absorbs. Unlike a greenhouse, the greenhouse gasses do not prevent heat being conducted to outside of the earth, as energy can only exist as heat when it is absorbed by matter, and outside the earth there is a vacuum. It only stops radiation reaching the outside universe.

There is growing concern amongst scientists that anthropologic activity could be increasing the quantity of greenhouse gasses in the atmosphere to an extent that is likely to have an effect upon the earth’s climate. Certainly, the burning of fossil fuels produces around seven billion tonnes of CO
2 per year, but the question is what effect this would have. In theory, less energy should be leaving the atmosphere, and so, in theory, the average global temperature would increase.  For reasons including the prevailing wind direction and the way that heat is transferred, the areas that would be most affected are the poles where, the ice sheets which hold most of the world’s fresh water reside. If the temperature rises above freezing point for a long enough period of time, probably during the summer, then the ice caps partially melt. The water would passes directly into the oceans that encircle the ice sheets. This happens every year naturally, but if global warming were occurring, the amount of ice that melts each year would increase to the point that less water freezes during the winter than melts during the summer. The more frequently this happens, the greater the amount of ice that would melt the next year as the reduced quantity of ice would mean an increased surface temperature. Eventually, the temperature could, in the Arctic at least, never drop below 0°C, so not even the fresh water would freeze. This is far less likely to occur in the Antarctic, as the land is considerably more mountainous, and there is a whole continent upon which the ice sheet rests, helping to keep the water fresh and its melting point high (relatively). Still, huge amounts of water would be released, raising sea levels well above their current levels.

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Raised sea levels would bring disaster upon ‘small island states’, as they would lose most of if not all their land to the sea. Ergo the organisation AOSIS (Alliance Of Small Island States) pushes for immediate action to be taken to prevent global warming. Low lying land, such as the fens and most of Holland would also end up under the sea or become swamp-like marshes. Great Britain would lose much of its land, although Flitwick & Ampthill might be okay, as just out of Flitwick is the shoreline from the last time there was a complete end to ...

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