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"Figure
2:
Long records of
past changes in atmospheric
composition provide
the context for the
influence of anthropogenic
emissions.
Click
to enlarge
(a) shows changes in
the atmospheric concentrations
of carbon dioxide (CO2),
methane (CH4),
and nitrous oxide (N2O)
over the past 1000 years.
The ice core and firn
data for several sites
in Antarctica and Greenland
(shown by different
symbols) are supplemented
with the data from direct
atmospheric samples
over the past few decades
(shown by the line for
CO2
and incorporated in
the curve representing
the global average of
CH4).
The estimated positive
radiative forcing of
the climate
system from these
gases is indicated on
the right-hand scale.
Since these gases have
atmospheric lifetimes
of a decade or more,
they are well mixed,
and their concentrations
reflect emissions from
sources throughout the
globe. All three records
show effects of the
large and increasing
growth in anthropogenic
emissions during the
Industrial Era.
Click
to enlarge
(b) illustrates the
influence of industrial
emissions on atmospheric
sulphate concentrations,
which produce negative
radiative forcing. Shown
is the time history
of the concentrations
of sulphate, not in
the atmosphere but in
ice cores in Greenland
(shown by lines; from
which the episodic effects
of volcanic eruptions
have been removed).
Such data indicate the
local deposition of
sulphate aerosols at
the site, reflecting
sulphur dioxide (SO2)
emissions at mid-latitudes
in the Northern Hemisphere.
This record, albeit
more regional than that
of the globally-mixed
greenhouse gases, demonstrates
the large growth in
anthropogenic SO2
emissions during the
Industrial Era. The
pluses denote the relevant
regional estimated SO2
emissions (right-hand
scale).
[Based
upon (a) Chapter
3, Figure
3.2b (CO2);
Chapter
4, Figure
4.1a and b ( CH4)
and Chapter
4, Figure 4.2 (N2O)
and (b) Chapter
5, Figure 5.4a]"
Source
& © : IPCC
TAR SPM of WG I
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