Global Climate Change cont...
There is no doubt that CO2
is accumulating in the atmosphere. The record from Mauna Loa charts a
continuing rise in CO2concentration since measurements began in
1958, when the level was 315 ppm; the value had reached about 370 ppm by the
end of the 20th century, and hit more than 378 ppm in 2004. Important as
changes in atmospheric CO2 undoubtedly are, we need to be aware that
this is not the whole story of human-induced greenhouse forcing.
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In particular, monitoring
programmes established during the 1980s reveal an upward trend in the levels of
two other natural greenhouse gases as well – methane (CH4) and
nitrous oxide (N2O). But how do we know that the build up of all
three gases over recent decades is due to human intervention?
Changes in the
atmospheric concentration of (a) CO2, (b) CH4 and (c) N2O
over the past 1000 years.
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