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The Greenhouse Effect and Global Warming
The Greenhouse Effect
The greenhouse effect is a natural process that
occurs all the time and keeps average global
temperatures at around 17 c. Without it, the
average temperature at the surface of the Earth
would be about -18 c.
This effect is the result of the heat and the light of
the Sun that reaches our planet.
Some solar radiation is reflected back into space,
some is absorbed by the atmosphere and some
reaches the Earth's surface.
Some of this radiation reaching the Earth's surface
is reflected back as heat and is lost into space.
However, some is radiated back to Earth by clouds and the `greenhouse gases' that form part of the
The gases trap this heat close to the Earth's surface, keeping it warm.
The most important greenhouse gas is carbon dioxide partly because there is so much of it and partly
because it remains in the atmosphere longer than any other greenhouse gas.
It has been estimated that 50-70 per cent of global warming is due to carbon dioxide in the atmosphere.
It is mainly a result of human activities that the concentration of carbon dioxide is increasing, enhancing
the greenhouse effect and causing environmental concerns.
Another natural greenhouse gas is methane.
Methane is produced when microorganisms break down the organic molecules of which organisms are
This occurs mostly in two situations:
When decomposers break down the dead remains of organisms
When microorganisms in the intestines of primary consumers, such as cattle, digest the food that
has been eaten
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Global warming is the term for the increase in average global temperatures over the last century.
The Earth has always shown periodic fluctuations in temperature.
We cannot therefore say for certain that this recent temperature increase is due to human activities.
What we can say is that the concentration of carbon dioxide has risen since the industrial revolution.
We also know that carbon dioxide is a greenhouse gas.
Most scientists therefore think that these human activities have contributed to global warming.…read more
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Measuring Carbon Dioxide
To determine whether there is a correlation between the concentration of carbon dioxide in the
atmosphere and global temperatures requires measurements of both these factors over many thousands
It is possible to determine the age of fossils by measuring the amount of radioactive decay of an isotope
of carbon radioactive dating.
Fossil shells from beneath the ocean bed contain oxygen isotopes as well as carbon ones.…read more