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Increase of greenhouse gases
Increase of greenhouse gases
Measurements from Antarctic ice cores show that just before industrial emissions
began, atmospheric CO2 levels were about 280 parts per million by volume (ppm;
the units µL/L are occasionally used and are identical to parts per million by
volume). From the same ice cores it appears that CO2 concentrations stayed
between 260 and 280 ppm during the preceding 10,000 years. Studies using
evidence from stomata of fossilized leaves suggest greater variability, with CO2
levels above 300 ppm during the period 7,000-10,000 years ago, though others
have argued that these findings more likely reflect calibration/contamination
problems rather than actual CO2 variability.
Since the beginning of the Industrial Revolution, the concentrations of many of
the greenhouse gases have increased. The concentration of CO2 has increased by
about 100 ppm (i.e., from 280 ppm to 380 ppm). The first 50 ppm increase took
place in about 200 years, from the start of the Industrial Revolution to around
1973; the next 50 ppm increase took place in about 33 years, from 1973 to 2006.
PDF (96.8 KiB). Many observations are available on line in a variety of
Atmospheric Chemistry Observational Databases. The greenhouse gases with the
largest radiative forcing are:
Relevant to radiative forcing Gas Current (1998) Amount by volume Increase over
pre-industrial (1750) Percentage increase Radiative forcing (W/m2)
Carbon dioxide
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