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0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Fig. 5.9 Constant and linear approximations of global annual mean temperature deviation
measurements (relative to the 1961-1990 mean); from 1991 to 2000
p.t/ D ˛ C ˇt C t 2 :
(5.33)
That is, we want to determine constants ˛, ˇ and , such that p fits the data in
Tab le 5.1 as accurately as possible. This will eventually lead to a 3 3 system of
linear equations. In order to see that, we define
X
10
C t i
y i / 2 :
F.˛;ˇ;/ D
C ˇt i
(5.34)
i D1
Again, a necessary condition for a minimum of F is
@F
@F
@F
@
D
D
D 0:
(5.35)
Here,
1 X
˛ C ˇt i
y i D 0
@F
C t i
D 2
(5.36)
i D1
 
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