Geoscience Reference
In-Depth Information
Fig. 5.13 Global annual
fossil fuel carbon dioxide
emissions through year 2007,
in million metric tons of
carbon (
http://www.upload.
Global_Carbon_Emission_
by_Type_to_Y2004.png)
concentration values by the end of the century will constitute 540
970 ppm (pre-
industrial and present values are, respectively, 280 and 367 ppm). Changes of land
use are also an important factor of the global carbon cycle, but all carbon emitted to
the atmosphere due to land use will be assimilated by the land biosphere. This could
only lead to a decrease of CO
2
concentration within 40
-
70 ppm. As for the
prognostic estimates of the concentrations of other GHGs, they vary widely. So, for
instance, it is concluded from some estimates that the role of tropospheric ozone as
a greenhouse gas can be equal to the contribution of methane and will be sub-
stantial, as being the factor of deterioration of air quality over most of the northern
hemisphere.
The concentration of methane in the atmosphere increased by a factor of 2.5,
compared with that observed in 1750, and continues to grow. The annual rate of CH
4
increase was reduced, however, and became more variable in the 1990s compared
with the 1980s. From the beginning of 1750, nitrous oxide concentration
has increased by 16 %. With the implementation of the Montreal Protocol, con-
centrations of several halocarbon compounds functioning as GHG and ozone-
destructing gases either, have increased more slowly or started decreasing. However,
concentrations of their substitutes and some other synthetic compounds started to
grow rapidly (e.g., per
-
uoride, SF
6
).
As for the properties of atmospheric aerosol and its climatic impact, respective
current information has been reviewed in detail in (Kondratyev et al. 2003c;
Krapivin and Varotsos 2008). In this connection, it is pointed out again that the
supposed anthropogenic nature of the present global climate warming was explained
by the warming caused by the growth in GHGs concentrations (primarily CO
2
and
CH
4
), as well as cooling due to anthropogenic aerosols. However, if the estimates of
the
fl
uorocarbons, PFC, and sulphur hexa
fl
ciently reliable, then the
respective calculations of radiative forcing (RF) due to aerosol are very uncertain. Of
no less importance is the fact that, while the global distribution of the
“
greenhouse
”
warming can be considered as suf
“
greenhouse
”
RF is comparatively uniform, the case of the
RF is characterized by a
strong spatial-temporal variability (including changes of the sign of RF).
“
aerosol
”
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