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Greenhouse Gases (GHGs)
Definition & Concept: 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 warming the Earth) and transmit the rest
back into space in the form of infrared radiation. However, present in the
atmosphere are the greenhouse gases (known to constitute about 1% of the
atmosphere), which act as the greenhouse glass and prevent heat from being
loss into the space. The GHG's reflects the escaping heat energy back to
the Earth.
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:
| |
Lowest Temperature |
Highest Temperature |
Average Temperature |
|
Earth |
-88°C (-126°F) |
136°F or 58°C |
15.6°C (60°F) |
| Moon
(no atmosphere) |
-233°C (-387°F) |
123°C (253°F) |
-18°C (-0.4°F) |
| Mars
(thin atmosphere) |
-87°C(-125°F) |
-5°C (23°F) |
-33°C (-27°F) |
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 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
Characteristics of Greenhouse Gases.
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