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scaling (SDS). In both cases large-scale numerical modeling was carried out with
the use of the GCM model developed in the Australian Scienti
c-Industrial Centre
(CSIRO).
The results obtained show that the RegCM2 model reveals a stronger spatial
variability of the
fields of temperature and precipitation than the SDS model, which
leads, however, to a greater amplitude of the annual change of temperature, than the
models RegCM2 or GCM. The diurnal change of temperature turned out to be
weaker in the cases of SDS and GCM than RegCM2, and the amplitude of the
diurnal change of precipitation varied in the interval between those corresponding
to SDS and RegCM2. Calculations with RegCM2 reproduce both an increase and
decrease of probability of precipitation with a doubled CO
2
concentration, whereas
SDS gave only an increase of precipitation.
One of the causes of differences mentioned above could be the fact that the semi-
empirical model SFS is based on the data that refer only to surface level 700 gPa,
whereas in two other models the vertical structure of the atmosphere is taken into
account. This comparison does not permit, however, to draw a conclusion, which of
the results obtained re
the impact of forcing. To answer this
question and establish the cause of these differences, the numerical modeling should
be further improved.
One of the important illustrations of highly uncertain theoretical estimates of the
causes of climate change is a re-assessment of the role of the
fl
ects
“
correctly
”
Milankowich
mechanism
”
, as the main factor of paleodynamics of climate observed during the
last years.
According to the Milankowich theory (Mor
“
sse 2001), changes of
paleoclimate had been determined by latitudinal re-distribution of extra-atmo-
spheric insolation and in the annual change as a result of variations of the
parameters of the Earth
é
n and P
å
s orbit (especially it refers to glacial-interglacial cycles
during the Quaternary period) which include:
'
(1)
inclination of the rotation axis with respect to the orbital plane (
fl
(fluctuating
; average periodicity of vari-
ations constitutes 41,000 years and affects mainly the high-latitude insolation);
(2) precession of equinoctial points affecting the time of the onset of equinoxes
and solstices, which tells mainly on low-latitude insolation (precession is
characterized by dual periodicities 19,000 and 23,000 years); and
(3) eccentricity of the Earth
within 22
24.5
°
with the current estimate 23.4
°
-
s orbit which changes from almost circular to strongly
elliptical with a periodicity of about 95,800 years (these changes cause a
modulation of precession.
'
Milankowich supposed, in particular, that the summertime low-level insolation
in high latitudes is the cause of the onset of glaciations and formation of ice sheets.
The resulting increase of surface albedo determines the functioning of a positive
feedback which intensi
es the impact of insolation decrease. The summertime low-
level insolation was observed at a minimum angle of the orbit
'
s inclination, high
eccentricity, and at an apogee in the NH summer. According to Milankowich
'
s
calculations, this configuration took place 185, 115, and 70 thousand years ago.
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