The Greenhouse Effect & Global Warming

The Greenhouse Effect The Earth’s average temperature is increasing.

Earth Solar radiation travels from the Sun and passes through the atmosphere and is absorbed by the Earth’s surface. This is then re-emitted as heat radiation. The increasing levels of ‘greenhouse gases’ in the atmosphere are trapping this heat energy and preventing its escape into space. It is this trapped energy which is raising the Earth’s average temperature. The Greenhouse Effect

Greenhouse gases within the Earth’s atmosphere absorb some of this outgoing radiation and reflect it back to the Earth’s surface. As levels of CO 2 and other greenhouse gases increase, they trap even more of the outgoing heat radiation causing even more global warming. Some of this radiation is re-emitted from the earth as long wave radiation. About 80% of the short wave, infra red radiation emitted by the Sun penetrates the Earth’s outer atmosphere and warms the Earth. CO 2 The Greenhouse Effect

Use this interactive diagram to study the greenhouse effect...

The Greenhouse Gases The greenhouse effect is caused by build up in the atmosphere of a number of different gases, such as: carbon dioxide water vapour ozoneCFC’smethanenitrogen oxides

The Greenhouse Gases – Carbon Dioxide The increase in the amount of carbon dioxide in the atmosphere is a direct result of human activity. Most of the CO 2 is released as a result of the increase in the amount of fossil fuels burned over the past years. The CO 2 moves into the atmosphere and allows solar radiation in, but prevents radiant heat from escaping back into space. There is evidence that this increased temperature is changing the Earth’s climate and weather patterns. The polar ice caps are already melting and coastal flooding is now more likely. CO 2 is released when any fuel such as, coal, oil, gas, or petrol is burnt.

The Greenhouse Gases - Water Vapour Water vapour, a natural greenhouse gas, has both a positive and negative effect. Water molecules do trap infra red radiation, but clouds also reflect incoming solar radiation.

The Greenhouse Gases - Methane Methane is produced by the anaerobic conditions associated with growing rice. Grazing animals release methane due to their digestive processes. Methane is also released from decomposing organic matter in landfill sites.

The Greenhouse Gases - Nitrogen Oxides Nitrogen oxides are produced by the combustion in vehicle engines. They are also released into the atmosphere from inorganic fertilisers (ammonium nitrate).

The Greenhouse Gases - Ozone Ozone is a powerful greenhouse gas. However, ozone does play a vital role in the atmosphere as it protects the Earth from incoming ultraviolet radiation.

The Greenhouse Gases - CFC’s Chlorofluorocarbons (CFC) were traditionally used in fridges and freezers. Their use was banned to protect the ozone layer, but CFC’s also act as greenhouse gases.

Greenhouse Gases – Relative Significance Carbon dioxide gas is the greatest overall contributor to the greenhouse effect. However, as a molecule, CO 2 is the least efficient of the greenhouse gases in trapping infra red radiation.

Deforestation The causes of deforestation are complex, and driven by both the needs of local people and the competitive global economy. Major causes of deforestation include...

Causes of Deforestation  Commercial logging  Demand for fuel (wood)  Poverty – increases the need for peasant farmers to remove areas of forest in order to raise crops for self-subsistence  Commercial and non-commercial agricultural practices  Mineral and oil extraction  Development – the construction of houses, roads, industrial buildings and dams (which flood large areas)

The plants of the forest remove CO 2 from the atmosphere for photosynthesis. The destruction of rainforests destroys this major carbon- dioxide ‘sink’ and releases CO 2 into the atmosphere. Releasing carbon dioxide into the atmosphere enhances the greenhouse effect, and could contribute to an increase in global temperatures (Global Warming). Deforestation and the Carbon Cycle Since accurate measurements of the amount of carbon dioxide in the air began at Mauna Loa in Hawaii in 1957, concentrations have risen from 315 parts per million to 381 parts per million. CO 2