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Greenhouse gases - Resource Centre

Climate Change
Myth or Real?

What are Greenhouse Gases

Greenhouse gases play an important role in the regulation of the Earth's energy balance.

Greenhouse gases basically consist of water vapour, carbon dioxide, methane, nitrous oxide, ozone and CFC's.

The natural greenhouse effect is a warming process whereby the greenhouse gases in the atmosphere trap the infra red heat that is trying to escape back into space.

The greenhouse gases then raise the temperature of the lower atmosphere and the Earth’s surface. During the last 200 years, the atmosphere has become increasingly polluted by man. These increased greenhouse gases have enhanced the natural greenhouse effect, contributing to global warming.

The amount of carbon dioxide (CO2) in the atmosphere has increased by 35% since the Industrial Revolution, which began in the 18th century,  The actual concentration of CO2 infact is now higher than at any point in the past 650,000 years.


What are the Greenhouse Gases


The Earth's greenhouse effect is based on the concentration of a few greenhouse gases in the atmosphere.

Water Vapour creates the most global warming but generally is not directly influenced by human activity.

These are the greenhouse gases that can be attributed to human activity:

• Carbon dioxide (CO2). The burning of fossil fuels such as coal, oil and gas is the main source of carbon dioxide emissions with deforestation making a significant contribution. CO2 accounts for 75% of the warming effect from human created greenhouse gases.

• Methane (CH4). Accounts for around 14% of human created greenhouse-gas emissions. The main sources are agriculture, fossil fuel extraction and the decay of organic waste in landfill sites. Methane doesn't persist in the atmosphere as long as CO2, though its warming effect is much more potent for each gram of gas released.

• Nitrous oxide (N2O). Accounts for around 8% of the warming impact of current human greenhouse-gas emissions. Key sources include agriculture (especially nitrogen-fertilised soils and livestock waste) and industrial processes. Nitrous oxide is even more potent per gram than methane.

• Fluorinated gases ("F gases"). Account for around 1% of the warming impact of current human greenhouse-gas emissions. Key sources are industrial processes. F-gases are even more potent per gram than nitrous oxide.

Human activity also changes the planet's temperature in other ways. For example, vapour trails from planes, soot from fires and and tropospheric ozone created indirectly by local pollution all tend to increase warming. On the other hand, aerosol particles produced by some vehicles and industrial processes tend to bounce sunlight away from the earth, temporarily counteracting some of the warming caused by man-made greenhouse gases.

Why greenhouse gases have increased

There are 3 important ways that Human activity is changing the amount of greenhouse gases in the atmosphere:

1. Rain Forests are being cut down

Trees absorb carbon dioxide so with fewer trees more carbon dioxide builds up in the atmosphere. Also the agriculture and industry that replaces the forests can often be a source of emissions. The Intergovernmental Panel on Climate Change (IPCC) estimates that deforestation produces 5.9 billion tonnes of CO2 per year or 18 per cent of global CO2.

2. Fossil fuels are being burned

Burning fossil fuels like coal, oil and gas  to generate heat or to power transport for example, releases greenhouse gases. In 2005, burning fossil fuels emitted about 27 billion tonnes of carbon dioxide.

3. The world’s population is growing

A growing population is leading to an increased demand for food, livestock and energy which is in turn leading to increased emissions.

See also The Causes of Climate Change


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