1. Is our climate changing?

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The earth's climate is continually changing. In the past this has been the result of 'natural' phenomena such as alterations in the earth's orbit or in the energy released by the sun or in the earth-atmosphere system itself. For example, one of the reasons put forward to explain the sudden disappearance of the dinosaurs 25 million years ago is the collision of a large asteroid with earth. The impact caused debris to enter into the atmosphere, blocking off sunlight, causing plants to die and starving the dinosaurs.

However, one of the most important issues the global human community faces today is the possibility that human activity is now sufficiently intense that we are altering the the earth-atmosphere system (EAS) and that the climate is changing as a result. Some of the most important environmental issues of today are those associated with a changing climate. As examples: the creation of CFC gases has been linked to the Ozone hole which allows more intense (and cancer causing) radiation to reach the earth's surface; the burning of coal and oil produces gases which are converted into acids in the atmosphere and return to earth as acid rain, destroying forests and poisoning streams. One of the most controversial of these global issues is that of 'global warming' and the Greenhouse effect.