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The data comes from a 1999
article in Nature which discussed Antarctic ice cores.
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Bottom scale shows 10,000
years per tick, with 1850 at the far right where it says 0. The far left is -420,000 years.
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Bottom red line is
temperature in celsuis, about 1 degree C = 2 degrees Farenheit. Note how in Antarctic temperature
has varied cyclically from
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About -10C to about +2
C. Also note the red
temperature band at about 0-2 C, above 1850. This is the last 10,000 years,
all of known civilization right here.
This is the
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Climate our society has
known. It is a tiny range
relative to the past. Also note
how fast we come out of the depths of the ice ages. It happens very,
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very quickly, and the cause
of this is under active investigation.
This is Ôabrupt climate changeÕ. It appears that glaciers take tens of thousands of years
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To generate, yet melt very
quickly. This may have
important ramifications for the ice on the planet now, and the potential for
large sea level rise.
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Green line in middle graph
is methane, a very potent greenhouse gas (about 20x as powerful at Carbon
Dioxide). Note how it varies
from about 400 parts per
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Billion to about 700 parts
per billion (ppb) over the last 420,000 years.
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Blue line in top graph is
carbon dioxide. Note how it varies from about 180 parts per million to about
280 parts per million (ppm) over the last
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420,000 years.
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HereÕs what the animated
lines show: (youÕll need to start a slide show to see this)
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Animation 1
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1)The orange bars on the Temperature graph show the 100,000-year long
slides into past ice ages. The
ice ages are brought on
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by subtle changes in the
EarthÕs orbital parameters – the roundness of our orbit around the sun
(eccentricity), the tilt of the earthÕs axis (inclination) and
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Something called precession
– how close the poles are to the sun during winter and summer. Believe it or not, these changes can
bring on ice ages, and periods
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Of warmth.
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Animation 2 and 3
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2) The solid black lines
show how the methane and carbon dioxide concentrations are timed exquisitely
with the temperature changes.
This is because as the
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Earth warms the oceans give
off carbon dioxide (imagine heating a can of Coke on the stove), and because
as it warms biological activity generates more methane.
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As this happens both Co2
and CH4 provide additional warming (a Òpositive feedback loopÓ) and hence
create more warming. As it
cools the exact opposite
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happens and cooling begets
more cooling. These feedbacks are the crux of the science of global warming.
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Animation 4
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3) Now reveal the
extensions of the graphs on the far right side. You can see just how out of whack carbon dioxide and
methane are compared to historical norms. And everyone thinks carbon dioxide will go to AT LEAST
550 parts per million and may go as high as 1000 ppm. The system has never
been ÔtweakedÕ in this fashion in about 1m years, and this is why scientists
are so concerned.
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