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(6) Have climate variability and climate extremes changed?
(7) Are observed trends internally coordinated?
In order to answer the above questions, the reliability of observational data is
fundamental. Adequate empirical diagnostics of climate remain impossible without
such observational data. Yet the information concerning numerous meteorological
parameters, so very important for documentation, detection and attribution of cli-
mate change, remains inadequate for the drawing of reliable conclusions. This is
especially true for the global trends of those parameters (e.g., precipitation), which
are characterized by a great regional variability.
Folland et al. (2002) have answered some of the questions above. A comparison
of the secular change of global average annual sea surface temperature (SST), land
surface air temperature (LSAT), and nocturnal marine air temperature (NMAT)
over the ocean for the period 1861
2000 on the whole revealed some similarity,
though the warming in the 1980s from LSAT data turned out to be stronger, and the
NMAT data showed a moderate cooling at the end of the 19th century not
demonstrated by SST data. The global temperature trend can be interpreted
cautiously as equivalent linear warming over 140 years, constituting 0.61
-
°
Cata
±
°
95 % con
dence level with an uncertainty range of
0.16
C. Later on, in 1901 a
°
±
°
warming by 0.57
C. These
estimates suggest that at the beginning from the end of the 19th century, an average
global warming by 0.6
C took place with an uncertainty range of
0.17
°
C took place, with the interval of estimates corresponding
to a 95 % con
C.
The spatial structure of the temperature field in the 20th century was characterized
by a comparatively uniform warming in the tropics and by a considerable variability
in the extratropical latitudes. The warming between 1910 and 1945 was initially
concentrated in the Northern Atlantic and the adjacent regions. The Northern
Hemisphere was characterized by cooling between 1946 and 1975, while in the
Southern Hemisphere some warming was observed during this period. The temper-
ature rise observed during the last decades (1970
dence level equal to 0.4
0.8
°
-
2000) turns out, on the whole, to
have been globally synchronous and clearly manifested across Northern Hemisphere
continents in winter and spring. In some Southern Hemisphere regions and in the
Atlantic, however, a small all-year-round cooling was observed. A temperature
decrease in the Northern Atlantic between 1960 and 1985 was later followed by an
opposite trend. On the whole, the climate warming over the period of measurements
was more uniform in the Southern Hemisphere than in the Northern Hemisphere. In
many continental regions between 1950 and 1993, the temperature increased more
rapidly at night than during daytime (this does not refer, however, to coastal regions).
The rate of temperature increase varied from 0.1 to 0.2
-
C/10 years.
According to the data of aerological observations, the air temperature in the
lower and middle troposphere was increasing after 1958 at a rate of 0.1
°
C/10 years,
but in the upper troposphere (after 1960) it remained more or less constant. A
combined analysis of the aerological and satellite information has shown that in the
period 1979
°
2000 the temperature trend in the lower troposphere was weak,
whereas near the land surface it turned out to be statistically signi
-
cant and reached
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