Geoscience Reference
In-Depth Information
2
400
1.8
1.6
350
1.4
1.2
300
1
0.8
0.6
250
1840
1880
1920
1960
2000
1750
1800
1850
1900
1950
2000
(b) Year
(a) Year
330
325
320
315
310
305
300
1988
1992
1996
2000
2004
2008
2012
(c) Year
Figure 12.8. Temporal changes in tropospheric mixing ratios of (a) carbon dioxide, (b) methane, and (c) nitrous
oxide. Data for carbon dioxide were from Siple Station, Antarctica, ice core for 1744-1953 (Friedli et al., 1986)
and from Mauna Loa Data Center (n.d.) for 1958-2009. Data for methane were from Law Dome ice core,
Antarctica, for 1841-1978 (Ethridge et al., 1992); from Carbon Dioxide Information Analysis Center (CDIAC;
n.d.) at Barrow, Alaska, for 1983-1995; and from Prinn et al. (2000) at Trinidad Head, California, for 1995-2010.
Nitrous oxide data were from Mauna Loa Data Center (n.d.).
Because aerosol particles are the leading cause of air
pollution mortality, reducing both cooling and warm-
ing particles is desirable from a public health perspec-
tive. As such, a strategy that involves reducing particle
and greenhouse gas emission simultaneously is bene-
ficial for reducing both health and climate problems
simultaneously (Chapter 13). Alternatively, because the
sources of warming particles, fossil fuel and biofuel
soot, differ from sources of cooling particles, a strategy
of selectively controlling fossil fuel and biofuel soot
together with greenhouse gases would address both cli-
mate and air pollution health problems simultaneously.
Figure 12.8 shows changes in the ambient mixing
ratios of CO 2 (g), CH 4 (g), and N 2 O(g) since 1750,
1840, and 1988, respectively. The historical CO 2 (g) and
CH 4 (g) data originate from ice core measurements. The
more recent data in all cases originate from ground-
based outdoor measurements. In 1958, Charles David
Keeling began tracking the mixing ratio of CO 2 (g) at
Mauna Loa Observatory, Hawaii. His record, shown in
detail in Figure 3.11 and in less detail in Figure 12.8a, is
the longest continuous ground-based record of the gas.
Whereas CO 2 (g) mixing ratios have increased continu-
ously through 2011, CH 4 (g) mixing ratios began to level
off in the 1990s and 2000s. However, they increased
again from 2007 to 2010 (Frankenberg et al., 2011;
Figure 12.8b).
The reason for the increases in tropospheric mix-
ing ratios of CO 2 (g), CH 4 (g), and N 2 O(g) over time
is the increase in their anthropogenic emissions cou-
pled with a slow removal rate. Figure 12.9 shows the
anthropogenic emission rates of CO 2 (g) between 1750
and 2007 (Boden et al., 2011). During this period,
12.2.4. Trends in Mixing Ratios and
Emissions of Gases and Particles
Since the mid-1800s, the tropospheric mixing ratios of
CO 2 (g), CH 4 (g), and N 2 O(g) have increased substan-
tially. These gases are relatively well mixed in the lower
atmosphere. In addition, black carbon emissions have
increased.
 
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