With the exception of stratospheric ozone, all greenhouse gases discussed throughout section 6.4 have increased in concentration in the atmosphere over the last 200 years since the beginning of the Industrial Revolution. Pre-industrial and current concentrations of the key greenhouse gases, and their recent rates of increase (IPCC, 1995), are displayed in Table 6.2.
Table 6.2. Pre-industrial and 1992 atmospheric concentrations of greenhouse gases
|
CO2 |
CH4 |
N2O |
CFC-12 |
|
|
Pre-industrial concentration |
280ppmv |
700ppbv |
275ppbv |
zero |
|
Concentration in 1992 |
355ppmv |
1,715ppbv |
310ppbv |
503pptv |
|
Rate of change of concentration during 1980s |
1.5ppmv/a |
13ppbv/a |
0.75ppbv/a |
20pptv/a |
|
Atmospheric adjustment time |
50-200 yrs |
12-17 yrs |
120yrs |
102yrs |
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