Greenhouse Effect

The greenhouse effect, first discovered by Joseph Fourier in 1824, and confirmed by Svante Arrhenius in 1896, is the process by which an atmosphere warms a planet. The term greenhouse effect may be used to refer to two different things nowadays: the natural greenhouse effect, which refers to the greenhouse effect which occurs naturally on Earth, and the enhanced greenhouse effect, which results from human activities.

While the greenhouse effect is a natural process, the enhancement of this process through human activities is causing widespread concern. Nine of the ten warmest years in the instrumental record have occurred since 1990. The global average surface temperature in 2002 was approximately 0.5o C above the 1961-90 averages and replaced the 2001 record as the second warmest on record (source: World Meteorological Organisation 2002).

Since the Industrial Revolution, mankind has been releasing extra quantities of greenhouse gases into the atmosphere, which trap more heat, enhancing the natural greenhouse effect. Processes such as the burning of fossil fuels, industrial operations and forest clearing release carbon dioxide, methane and nitrous oxide into the atmosphere.

The most significant greenhouse gases are water vapour, carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons (CFCs - made by humans). Water vapour contributes about 75% to the natural greenhouse effect, but the input of vapour into the atmosphere from human activity is so much smaller than natural levels that it is usually disregarded. However, any changes in the amount of water vapour in the atmosphere as a result of the enhanced greenhouse effect would affect the climate as a whole.

The implications of an enhanced greenhouse effect are difficult to count, but include a range of changes to the climate. There would be more than just a simple rise in temperature. It would also include changes to average and seasonal rainfall, and an increase in the frequency and severity of extreme