316
C02 [ppmv]
CH4 [ppbv]
700
4000
650
3500
600
3000
550
500
2500
450
2000
400
1500
350
300
1000
250
500
1860 1900
1950
2000
2050
2100
1860 1900
1950
2000
2050
2100
N20 [ppbv]
CFCs [pptv] group A
420
900
CFG-11
800
- - - - CFG-12
/'
400
-
-
-
- HCFC-22
I
700
-
-
HFG-125
380
- -
- - HFG-l34a
600
/
360
y\
500
/
340
~'
400
320
,'''''
300
/
300
200
/
280
100
260
0
1860 1900
1950
2000
2050
2100
1860 1900
1950
2000
2050
2100
Figure 12: Greenhouse gas concentrations as prescribed in the climate change experiment.
The years 1860-1990 according to observations, the years 1990-2100 according to IPCC
scenario IS92a. From IPCC 1994.
course be calculated from the known radiative conditions and greenhouse
gas concentration at the time, but this is excessively computationally demanding and has not yet been undertaken.
Table 3 gives the radiative forcing (W / m 2 ) for the different greenhouse
gases at the tropopause level. For the period 1750 (beginning of the industrialization) to 1990 the concentrations are based om measurements.