Environmental Engineering Reference
In-Depth Information
Table 1.7
Characteristics of Greenhouse Gases in the Atmosphere in 1998
Greenhouse gas
CO
2
CH
4
N
2
O
O
3
CFC-11
HFC-23
Concentration in
ppm
365
1.745
0.314
0.03
0.000268
0.000014
Atmospheric lifetime
in years
5-200
12
114
0.1
45
260
Rate of
concentration
change in %/year
0.4
0.4
0.25
0.5
-0.5
3.9
Specific global
warming potential
1
32
150
2000
14,000
10,000
Global warming
share in %
61
15
4
<9
11 (all fluorocarbons)
Source:
IPCC, 2001
ppmv (parts per million by volume) in 1850 to 372 ppmv in 2002 (Blasing and
Jones, 2003). If there is no change in energy policy, this development will
accelerate in the coming decades. Today's carbon dioxide concentration in the
atmosphere is already higher than at any other time during the past 250,000
years.
Anthropogenic
methane
(CH
4
) sources are coal mining, production of
natural gas, waste disposal and agriculture such as cattle farming or cultivation
of rice. The production and use of fossil fuels causes the majority of methane
emissions. Although the concentration of methane in the atmosphere is less
than 1 per cent of the carbon dioxide concentration, methane has a high
climate change potential (15 per cent contribution to the greenhouse effect),
i.e. the global warming potential of methane is much higher than that of
carbon dioxide. Therefore, much smaller emission quantities are critical. In
1998 the average tropospheric concentration of 1.745 ppmv of methane had
already more than doubled compared to the pre-industrial concentration of
0.7 ppmv.
Chlorofluorocarbons
(CFCs) have been used in large quantities as
refrigerants or propellants in spray cans. CFCs fell into disrepute mainly due
to their destructive influence on the ozone layer in the stratosphere at a height
of 10-50 km. International agreements to reduce CFC production in a step-
by-step process initially slowed down the increase and finally decreased the
concentration in recent years. However, the greenhouse potential of CFCs (11
per cent contribution to the greenhouse effect) was no significant argument in
the CFC reduction discussions. Some substitutes for CFCs such as HFC-23 or
R134a have significantly lower ozone-destroying potential but nearly the same
greenhouse potential.
Fire clearance of tropical rain forests and the use of nitrogenous fertilizers
are sources of anthropogenic
nitrous oxide
(N
2
O). In 2001 the atmospheric
N
2
O concentration of 0.317 ppmv was only 16 per cent above the pre-
