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Greenhouse Effect and Global Warming

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The Greenhouse Problem

A number of the gases we are putting into the atmosphere have the effect of trapping energy that comes to the earth as sunlight but which would otherwise be radiated back into space. The main contributor is carbon dioxide, accounting for about half the greenhouse effect. Humans generate about 24 billion tonnes of carbon dioxide each year, mostly from the burning of fossil fuels (coal, oil and gas) in rich countries. The carbon dioxide content of the atmosphere has increased by about 25% since humans began to use fossil fuels in large quantities 150 years ago. The concentration is now around 350 ppm and increasing by about 1.5% p.a. The effects cant be predicted with confidence but this increase could result in a 1-2 degree rise in average global temperature by 2030. The expected rise at the poles is much greater. If the greenhouse effect continues into the 22nd century then polar ice would begin to melt eventually bring about a sea rise of perhaps a hundred meters. Even a half metre rise would cause huge problems for the many people who live on low lying islands and in coastal regions. Probably the most undesirable effects will be hotter and drier climates in many Third World regions such as the African Sahel, where millions of people even now have difficulty growing enough food , and more frequent occurrence of extreme climatic events such 98 storms, floods, droughts and cyclones. These can devastate food production. It is possible that positive feedback effects from several sources could suddenly produce a catastrophic runaway greenhouse effect. For example,

Plant Many Trees It doesnt take long to realize that there is no realistic chance of solving the greenhouse problem by planting trees to remove carbon dioxide from the atmosphere. Firstly wed have to plant something like the area of Australia, and secondly this would only take carbon from the atmosphere while the trees were growing. Similarly, increasing the use of nuclear energy in order to cut coal use would not make much difference. Burning coal to produce electricity contributes only a small fraction of the carbon input, carbon constitutes only about half of the greenhouse problem, and to build all the reactors needed would require a great deal of energy and would therefore help to make the greenhouse problem worse for possibly 50 years. ...

  • As the warming dries out the Arctic tundra it begins to rot, releasing greenhouse gases.

  • As the tropical rainforest is destroyed we lose the cloud, t heir moisture generates. That cloud presently reflects much solar energy back into space, cooling the earth.

  • As the warming reduces the formation of polar ice each year less salt is separated to fall to the bottom causing the huge currents that take carbon-rich water down.

  • As these currents diminish less nutrients are brought up to feed the plankton which take in much carbon.

  • As the oceans warm and become more polluted coral reefs dissolve, ceasing to take carbon from the atmosphere and releasing their carbon to the ocean. It seems that the global atmospheric system can flip from one state to another fairly quickly. Some ice ages have come and gone relatively suddenly. The worry is that human activity could tip the system into a new state, for example, bringing on a new ice age. Nature moves 100 times as much carbon into and out of the atmosphere as humans do, so we might trigger or lever huge shifts and runaway effects in natures processes.