The term Global Warming has been in common usage for some
time and usually refers to recent warming of Earth's
atmosphere,which also implies a manmade or human influence.
Earth's atmosphere comprises many gases: oxygen, nitrogen,
carbon dioxide (hereafter abbreviated to CO2) and water
vapour, to name a few. These gases are collectively called
greenhouse gases and they keep the Earth's temperature at a
comfortable 15°C. Without them Earth would be a chilly
-18°C.
Since pre-industrial times, usually taken to be before
1750, we know from ice-core records that CO2 levels were
about 280 ppm,that's 280 parts of CO2 per million parts of
air. As industrialisation got underway humankind started to
farm the land more intensely than ever before, which
included deforestation for agriculture and settlements.
Later - since about 1850 or so - the burning of fossil
fuels for energy and transport has added considerably to
greenhouse gas levels, particularly CO2.
This has resulted in CO2 levels increasing to about 385
ppm, a rise of about thirty-seven per cent from
pre-industrial levels - mainly as a result of burning
fossil fuels.
How do we know this?
Well, data from ice-core records that go back at least
650,000 years now show us that CO2 levels have fluctuated
naturally during this time between 280 and 300 ppm. CO2
levels have also been measured accurately from the top of
Mauna Loa Volcano in Hawaii since 1958, and results show an
increase in CO2 levels from 315 ppm to 385 ppm since that
time.
Therefore CO2 is now at eighty ppm more than it has been
for at least 650,000 years of Earth's history. It is a
known scientific fact that higher levels of greenhouse
gases will lead to higher temperatures, which appears to be
happening now. The world has warmed by an average of 0.74
degrees during the last 100 years or so. As a result of
this warming, polar ice has started to decrease and melt,
and so have Earth's land-based glaciers. This in turn is
causing sea levels to rise, which is putting low-lying
islands at risk of flooding or total submersion, and will
eventually threaten more and more of the world's coastal
cities and regions.
Things may get worse, however, because once Earth's
atmosphere starts to warm, the warming itself may cause
further positive feedback mechanisms to kick in. A warmer
atmosphere holds more water vapour, which is itself a
powerful greenhouse gas. This will in turn cause further
warming, and so on.
Melting ice results in more sunlight being absorbed by the
surrounding 'darker' water and land, and that results in
further warming, and more melting ice. Methane deposits
currently held in a frozen but stable state under the sea
and under the permafrost may be released as the oceans warm
and permafrost melts, which will cause further warming.
This is very worrying as methane is a potent greenhouse gas
and around twenty times more powerful than CO2 when talking
about it's ability to warm the Earth's atmosphere.
This is global warming in a nut shell, however there are of
course far more complex issues involved as global warming
will not affect the whole planet in the same way at the
same time. Some parts will experience more drought, some
parts more rainfall, and some parts more extreme weather
such as floods and heatwaves.
One thing is for sure,as the world warms, we will all know
about it...
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This article is taken from The A-Z of Global Warming, which
was published in September 2008 by Schmall World
Publishing. Please goto the following website for further
information on the book. http://www.a-zofglobalwarming.com
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