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Global Warming - Why we have a Problem By David Cotton - first published March 2007 CLIMATE CHANGE is nothing new
and there are sceptics who argue that the changes we are currently experiencing are more to do with the long term pattern
than with the activities of the human race. However, what is very new is the speed at which the temperature is changing. The
current rise is more than ten times faster than can be detected at any time in the past. Over the last half million years the temperature has varied by almost 10ºC with distinct peaks and troughs.
In the last trough, between ten and twenty thousand years ago, ice extended as far south as New York and, with the sea level
100 metres lower, you could walk on dry land from Alaska to Siberia. In the seventeenth and eighteenth centuries, during the
"little ice-age", the Thames regularly froze over. The temperature of the Earth results from
a delicate balance between the energy reaching us from the sun and the amount radiated back out again. When anything happens
to disturb this balance the temperature changes until a new balance is established.
In the past it has been minor changes in our orbit round the sun which have upset the balance,
now it is changes to the atmosphere. The atmosphere plays a major part in maintaining our temperature by
preventing some heat escaping back into space. Indeed, if we had no atmosphere at all, the earth’s temperature would
be similar to that on the moon, about 30ºC colder that it is now! Greenhouse Gases (GHGs) in the
atmosphere trap energy, as it tries to escape into space, and reflect it back to the surface. Like the glass in a greenhouse
these GHGs keep the space below, the "biosphere" we live in, warmer than it would otherwise be. Water vapour is
an important GHG but carbon dioxide (CO2) is the most significant "anthropogenic" one accounting for
well over half of mans’ impact on global warming. However, there are other GHGs including methane which is a produced
by both ends of a cow as well as from natural gas, landfill sites and marshland. Oxides of nitrogen are produced by vehicle
engines and aircraft and chlorofluorocarbons (CFCs) come from refrigeration systems. During the carboniferous
period, 300 million years ago, plants and plankton absorbed CO2 from the atmosphere and energy from the sun. Over
millions of years this was converted into coal, oil or natural gas, the fossil fuels we now use. When we burn them we release
all that energy, stored so long ago, and with it all the CO2 from which the fuels were made - it is this which
causes the trouble. In the
past it has been minor changes in our orbit round the sun which have upset the balance, now it is changes to the atmosphere.
The atmosphere plays a major part in maintaining our temperature by preventing some heat escaping back
into space. Indeed, if we had no atmosphere at all, the earth’s temperature would be similar to that on the moon, about
30ºC colder that it is now! Greenhouse Gases (GHGs) in the atmosphere trap energy, as it tries
to escape into space, and reflect it back to the surface. Like the glass in a greenhouse these GHGs keep the space below,
the "biosphere" we live in, warmer than it would otherwise be. Water vapour is an important GHG but carbon dioxide
(CO2) is the most significant "anthropogenic" one accounting for well over half of mans’ impact
on global warming. However, there are other GHGs including methane which is a produced by both ends of a cow as well as from
natural gas, landfill sites and marshland. Oxides of nitrogen are produced by vehicle engines and aircraft and chlorofluorocarbons
(CFCs) come from refrigeration systems. During the carboniferous period, 300 million years ago, plants
and plankton absorbed CO2 from the atmosphere and energy from the sun. Over millions of years this was converted
into coal, oil or natural gas, the fossil fuels we now use. When we burn them we release all that energy, stored so long ago,
and with it all the CO2 from which the fuels were made - it is this which causes the trouble. Both CO2 levels and temperature have changed in the last 1,000 years and they have increased
in parallel since the beginning of the industrial revolution. In 300 years we are using up all the fossil fuels it took nature
100 million years to make! If we go on at this rate a further temperature rise of several degrees is likely and this will
have a very serious impact on the climate.We can limit our use of fossil fuels both by using less energy
overall and by using renewable energy which does not release CO2 into the air. Renewables include hydro electricity,
wind and wave power and solar energy. Biofuels, about which we hear a great deal, are also an option. When these are burned
they release more CO2 into the air than using fossils fuels but they are "carbon neutral" because a matching
amount of CO2 was absorbed in growing the crops from which they were made. The solution
to the problem of global warming depends on both individual and collective actions. It needs us all to make some changes in
our habits, sometimes at little or no personal cost, and it requires governments, with our support and encouragement, to make
major policy decisions. Action is needed NOW. If you want to be involved why not join a local
group who are taking action. Visit http://www.dulwichgoinggreener.org We can limit our use of fossil fuels both by using less energy overall and by using renewable energy which
does not release CO2 into the air. Renewables include hydro electricity, wind and wave power and solar energy.
Biofuels, about which we hear a great deal, are also an option. When these are burned they release more CO2 into
the air than using fossils fuels but they are "carbon neutral" because a matching amount of CO2 was absorbed
in growing the crops from which they were made. The solution to the problem of global warming depends
on both individual and collective actions. It needs us all to make some changes in our habits, sometimes at little or no personal
cost, and it requires governments, with our support and encouragement, to make major policy decisions. Action is needed NOW.
If you want to be involved why not join a local group who are taking action. Visit http://www.dulwichgoinggreener.org
Composting - get stuck in!
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