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CLIMATE CHANGE FACT:
Globally, it is very likely that the 1990s was the warmest decade
and 1998 the warmest year on record. Records have been kept since
1861. |
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Resources / Scientific
Evidence For Climate Change |
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The fundamentals of climate change have long been understood
because they involve the same basic physics that keeps the earth
habitable. Heat-trapping 'greenhouse gases' in the atmosphere
(of which the two most important are water vapour - clouds-
and carbon dioxide, CO2) let through short wave radiation from
the sun but absorb the long wave heat radiation coming back
from the Earth's surface and re-radiate it (see Figure
1). These gases act like a blanket - and keep the surface
and the lower atmosphere about 33 deg. C warmer than it would
be without them. The Earth's greenhouse blanket is a good balance
between the extremes of our neighbours: Mars, which has no greenhouse
gases is a frozen wasteland without life; whilst Venus remains
trapped in a dense blanket of CO2 and is consequently a very
hot and hostile place, again without any possibility of life.
Source: The Carbon Trust, UK.
'It is possible that the global warming trend projected
over the course of the next 100 years could, without warning,
dramatically accelerate in just a handful of years - forcing
a qualitative new climatic regime which could undermine
ecosystems and human settlements throughout the world, leaving
little or no time for plants, animals and humans to adjust.
The new climate could result in a wholesale change in the
earth's environment, with effects that would be felt for
thousands of years.'
USA National Academy of Sciences, February 2002.
By drilling ice cores miles into the frozen ice in Greenland
and in the Antarctic we can get a detailed temperature and CO2
history of Earth's past. By obtaining an ice core sample 10,000
feet down in our ice sheets we are looking at ice made over
700,000 years ago and by analysing the minute bubbles of air
trapped in this ice scientists can tell what the earth's temperature
was at the time. In Figure 2 alongside, the
graph gives the temperature and carbon level history of the
planet over the past 400,000 years. Warm peeks interrupt long
periods of cold ice age conditions and it is easy to see the
direct correlation between temperature and CO2 levels: as the
greenhouse gases in the atmosphere rise, so does the temperature.
During the last 14,000 years the earth has had one of its most
stable periods in terms of temperature with small fluctuations
of only 1 degree centigrade - this coincides directly to the
stable period of 'civilisation' as we know it - conditions on
Earth are ideal for crop development, animal life and human
existence.
Figure 3 shows how CO2 levels rose after the
last ice age to a stable plateau of about 265 ppmv and the Earth's
temperature averaged out to 0 degrees centigrade + or - 1 degree
centigrade. The Lascaux Caves are dated at 14,000 years ago,
Poliochni 6000 years ago and Troy was 3000 years ago, all evolving
during the Earths 'stable' warm period. During the last 150
years, CO2 levels have increased dramatically to a present day
level of 380ppmv which is and will promote a direct rise in
the Earths temperature. This is the threat of climate change
- by the consequences of our life style we are forcing Earth
out of her stable temperature period, which is so conducive
to human existence, into the possibility of temperature rises
and global instability. It is easy to see that a predicated
Earth temperature rise of 3 degrees C would put the planet into
a position it has not experienced for a hundred thousand years.
During the last 200 years we have very accurate temperature
measurements which, since 1900 have been increasing steadily.
This temperature rise in now understood to be a direct consequence
of global industrial growth. The graph figures in
Figure 4 show the average global
surface temperature as measured (red line), compared to estimates
from a computer simulation, respectively without (left) and
with (right) the effects of human emissions included.
Source: Reproduced from Intergovernmental Panel on Climate
Change, 2001.
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