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anthropogenic land use changes on climate limited, however, by a consideration of
only the impact of land use dynamics, starting from 1,750, on surface albedo. The
obtained estimates gave an average F value equal to
m
−
2
with an uncer-
−
0.2 W
·
m
−
2
. Thus such estimates are highly uncertain, and this
concerns even the sign of F (a more complete consideration of biophysical, bio-
geochemical and biogeographical impacts of the land use evolution on climate has
led to the conclusion that in this case F > 0).
In this connection, of importance is a new range of potential global warming by
2,100 assumed in the IPCC-2001 Report (1.4
tainty interval 0
∕−
0.4 W
·
C) based only on the numerical
modeling data (and therefore it will inevitably change in future). Also, the problem
is that this new range cannot be directly compared with the earlier similar values.
From the viewpoint of reliability of the estimates of future climate change, of
importance is the use in the IPCC-2,001 Report of the term projections instead of
predictions, since the latter implies that the factors left out of account will not be
substantial in the future. It is unacceptability of the latter supposition that is the
reason why none of the specialists in the
−
5.8
°
field of numerical modeling will assert that
the climate can be predicted 100 years in advance. This conclusion con
rms the
results of numerical modeling carried out in (Andronova and Schlesinger 2001).
The complexity of the problem of prognostic assessments of climate, especially
of selecting the contribution of anthropogenic component is illustrated by the
remaining inconsistency of analysis of the climatic impact of clouds. Tsushima and
Manabe (2001) have analyzed the impact of cloud feedback (CF) on the formation
of the annual change of global mean SAT using the data of space observations of
the Earth
s radiation budget (ERB), bearing in mind an assessment of adequacy of
CF consideration in numerical climate models by comparing the calculated and
observed change of the global mean SAT. It follows from the observed data that the
global annual change of SAT is in phase with the annual change of SAT in the
Northern Hemisphere, and its amplitude constitutes 3.3 K (this in-phase character is
determined by concentration in the Northern Hemisphere of continents contributing
most to the formation of the amplitude of the annual SAT change).
Analysis of the data of the ERB components observations for the period from
February 1985 to February 1990 has shown that global mean values of both
shortwave and longwave radiative forcings (SWRF and LWRF) depend weakly on
the annual change of global mean SAT (the ERB data considered refer only to the
band 60
'
S). Thus the cloud cover dynamics causes neither increase nor
decrease in the annual change of SAT. The data on SWRF and optical properties of
clouds show that not only albedo but an amount and top height of clouds depend
weakly on SAT and hence, CF does not affect strongly the annual change of the
global mean SAT.
It could be drawn from this conclusion that the impact of CF on the annual
change of the global mean SAT or on the global warming is negligible. However,
this speculative opinion is dangerous in view of strong complexity of the spatial
°
N
60
°
-
field of SAT. Calculations with the use of three climate models which take into an
interactive account the dynamics of the microphysical properties of clouds have led
to the conclusion about a substantial
increase of the cloud top albedo with
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