Geoscience Reference
In-Depth Information
300
Table 2.4 Mean annual release and consumption of
CH 4 (Tg).
280
CO 2
260
Mean
Range
240
A Release
Natural wetlands
2.5
115
100-200
220
Rice paddies
110
25-170
˚C
0
200
Enteric fermentation
80
65-110
(mammals)
Gas drilling
-2.5
180
45
25-50
-5.0
Biomass burning
40
20-80
Termites
40
10-100
-7.5
Landfills
40
20-70
Total
c . 530
-10.0
B Consumption
Soils
160
120
80
40
0
30
15-30
Thousands of years (BP)
Reaction with OH
500
400-600
Figure 2.6 Changes in atmospheric CO 2 (ppmv: parts per million
by volume) and estimates of the resulting global temperature
deviations from the present value obtained from air trapped in ice
bubbles in cores at Vostok, Antarctica.
Source : Our Future World , Natural Environment Research Council
(NERC) (1989).
Total
c . 530
Source : Tetlow-Smith 1995.
Figure 2.7 Methane concentration (parts
per million by volume) in air bubbles
trapped in ice dating back to 1000 years BP
obtained from ice cores in Greenland and
Antarctica and the global average for AD
2000 (X).
Source : Data from Rasmussen and Khalil,
Craig and Chou, and Robbins; adapted from
Bolin et al . (eds) The Greenhouse Effect,
Climatic Change, and Ecosystems (SCOPE 29).
Copyright ©1986. Reprinted by permission
of John Wiley & Sons, Inc.
inates primarily from microbial activity (nitrification)
in soils and in the oceans (4 to 8 10 9 kg N/year), with
about 1.0 10 9 kg N/year from industrial processes.
Other major anthropogenic sources are nitrogen fertil-
izers and biomass burning. The concentration of N 2 O
has increased from a pre-industrial level of about 285
ppbv to 316 ppbv (in clean air). Its increase began
around 1940 and is now about 0.8 ppbv per year (Figure
2.8A). The major sink of N 2 O is in the stratosphere,
where it is oxidized into NO x .
Chlorofluorocarbons (CF 2 Cl 2 and CFCl 3 ), better
known as 'freons' CFC-11 and CFC-12, respectively,
were first produced in the 1930s and now have a total
atmospheric burden of 10 10 kg. They increased at 4 to 5
per cent per year up to 1990, but CFC-11 is declining
slowly and CFC-12 is nearly static as a result of the
Search WWH ::




Custom Search