The Greenhouse Effect
The ‘Greenhouse Effect’ is the natural process
by which our atmosphere traps some of the
Sun’s energy, warming the Earth enough to
support life. Without it, the Earth would be a
very cold place.
The Earth gets energy from the Sun in the
form of sunlight. Some bounces straight back
into space off the atmosphere, and the rest is
absorbed by the land, seas and atmosphere.
The energy that is absorbed into the surface of
the Earth is eventually released by giving off
a different form of energy – infrared radiation.
But before this radiation can escape to outer
space, greenhouse gases in our atmosphere
absorb some of it, making the atmosphere
warmer, and as the atmosphere gets warmer,
it makes the Earth's surface warmer too.
The Carbon Cycle
So the Greenhouse Effect is extremely
important and essential to our survival. These
'greenhouse gases' are present naturally.
However, human activity is increasing their
concentrations. These gases, such as methane
and carbon dioxide are 'tuned' to absorb
energy at infrared wavelengths (as the energy
is released from the Earth's surface). This
'excites' the gas molecules, warming the
atmosphere – energy is re-emitted from the
molecules in all directions.
At this point, again, some energy is released
back into space, but some is re-directed
back to the surface to warm it still further.
The more greenhouse gases we have in the
atmosphere, the more they work to increase
the temperature on the surface.
Peter Reid 2009
The main greenhouse gas of concern is carbon
dioxide (CO2). The Carbon Cycle demonstrates
how a finite amount of carbon is stored in all living
matter, the sea, fossil fuels and the atmosphere.
The transfer between these stores roughly balance
each other out – plants absorb carbon as they
grow, but when they die and decay, they release it.
However, when humans influence the cycle – for
example by cutting down trees or burning fossil
fuels, they release the extra carbon straight into
the atmosphere, rather than the cycle following its
natural patterns.
This added carbon dioxide into the atmosphere
increases the greenhouse gases, increasing the
greenhouse effect, leading to global warming.
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