- Greenhouse gases are gases that trap heat in the earth’s atmosphere. They are called greenhouse gases because they act like the glass of a greenhouse. The glass of a greenhouse lets in heat from the outside sunshine but prevents heat from being lost from the greenhouse to the outside. The energy from the sun is transmitted to the Earth in the form of short wave ultraviolet (UV) radiations. The earth absorbs some of the energy (responsible for required warming of the Earth) and transmit the rest back into space in the form of infrared radiation. However, atmospheric greenhouse gases (about 1% of the atmosphere), prevent the heat from escaping space. GHG's reflect the escaping heat energy back to the earth, making our earth hotter than required.

GHGs friends or foes?:

Greenhouse gases occur naturally in the atmosphere and are believed to be responsible for maintaining the temperature of the Earth at levels that make the Earth bearable for living. Without the greenhouse effect of the GHGs, the Earth temperature would either be very cold or be extremely hot and will be difficult for human living. The average temperature of the Earth is about 15.6°C (60°F) and the extremes are: -126°F or -88°C to 136°F or 58°C. It is believed that without greenhouse effect, the Earth's average temperature can be as low as -18°C (-65°F). Not only that, the extreme temperatures will vary very widely.

The moon, which has no atmosphere, has an average surface temperature of -18°C and a temperature variation of -387°F or -233°C (at night) to 253°F or 123°C during the day! The moon has got no atmosphere to block some of the the UV rays from the Sun (hence reducing heat on the Earth during hot times, particularly day times) or to trap heat to warm up during cold times, particularly night times .

Mars has a very thin atmosphere and an average temperature of -33°C(-27°F) and extreme variations of -125°F or -87°C to 23°F or -5°C.

Temperature comparisons between Earth, Moon and Mars:

So if GHGs are that useful for regulating the Earth's temperature, then what is the fuss about? The natural balance of the Earth's energy will work well for the good living. It explains why man will not live in the moon and not in Mars but on Earth. However, the human dimension to GHG generation is shifting the balance and warming up the Earth. Scientists and our daily experiences/observations have produced several data to show that the Earth is warming up (Global Warming) due human activities that are increasing the amount of GHG's present in the atmosphere. Global warming comes with its attendant problems of flooding, hurricanes etc which are causing devastation to human lives. That is how GHGs become evil or rather how "human GHGs" become evil.

The main greenhouse gases

The main greenhouse gases defined within the context of the Kyoto Protocol are:

• Carbon Dioxide (CO2);
• Methane (CH4);
• Nitrous Oxide (N2O);
• Hydrofluorocarbons (HFCs);
• Perfluorocarbons (PFCs); and
• Sulphur Hexafluoride (SF6)

For the characteristics of these GHGs, quantities naturally present in the atmosphere, humanly generated components and other information go to the section on Characteristics of Greenhouse Gases.

• Causes of Climate change - Edugreen
• Intergovernmental Panel on Climate Change (IPCC)
• United Nations Framework Convention on Climate Change
• World Meteorological Organization (WMO)
• United Nations Environmental Programme (UNEP).