The message
from Terry Fields contains these words:

Several points spring to mind he

- the polynomials are, well, rubbish

Well they are no use for this sort of application anyway.

- the 10- and 20-point moving averages shift everything to the
right

- the 5-point moving average picks up the downturnclearly afetr 2 to
3 years, as might be expected.

The thing that appears to come out of this exercise is that to pick up
trends at the earliest opportunity, long moving averages are not the
tool to use. Hadley seems to use a (weighted) 20-pointer; I'll bet
they've done every kind of data run, in a more sophisticated manner
then we have, and have a good idea of the current position.

The Met Office filter is 21 points and seems to do the job very well
except for the limits of the sequence and even there I am coming to the
view that it is difficult to specify something else that lessens the
weighting effect of the final year without introducing another factor
potentially at least as bad.

It is generally accepted that El Nino and La Nina episodes have a
significant warming or cooling effect respectively so the Met Office may
well have a graph somewhere that attempts to compensate for those
factors.

One of the bloggers said that the 'downturn' data doesn't appear on
the Hadley's 'Myth' page....I can't help wondering why. Perhaps, like
Micawber, they're waiting for something to turn up (or down).

Those who see a definite trend already are cherry picking their data.
Given a few more years the downturn will become evident if it is
anything other than a transient event. The figures below are for the
smoothed curve 1850 - 2060 using the inverted around 2005 which shows
the downturn clearly and centred on 2005. (I hope no one picks these
figures up and takes the forward projection as gospel.)

-0.09
-0.08
-0.08
-0.08
-0.09
-0.11
-0.13
-0.15
-0.17
-0.19
-0.19
-0.19
-0.18
-0.15
-0.12
-0.07
-0.04
-0.01
0.01
0.02
0.02
0.01
-0.00
-0.01
0.00
0.03
0.06
0.09
0.11
0.11
0.09
0.07
0.05
0.02
0.01
-0.00
-0.00
-0.00
-0.01
-0.02
-0.03
-0.05
-0.06
-0.06
-0.05
-0.02
0.00
0.02
0.03
0.02
0.00
-0.03
-0.06
-0.09
-0.11
-0.12
-0.14
-0.17
-0.19
-0.21
-0.22
-0.21
-0.18
-0.15
-0.13
-0.12
-0.11
-0.11
-0.10
-0.09
-0.07
-0.06
-0.05
-0.04
-0.02
-0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.07
0.09
0.12
0.15
0.19
0.23
0.26
0.27
0.28
0.27
0.26
0.23
0.19
0.15
0.11
0.09
0.07
0.08
0.09
0.10
0.10
0.10
0.10
0.11
0.13
0.15
0.17
0.18
0.18
0.17
0.15
0.14
0.13
0.13
0.15
0.16
0.18
0.19
0.19
0.19
0.19
0.18
0.19
0.21
0.24
0.27
0.31
0.33
0.35
0.35
0.35
0.35
0.35
0.37
0.39
0.41
0.42
0.43
0.44
0.44
0.45
0.47
0.50
0.54
0.57
0.60
0.62
0.64
0.66
0.69
0.71
0.72
0.72
0.72
0.71
0.69
0.66
0.64
0.62
0.60
0.57
0.54
0.50
0.47
0.45
0.44
0.44
0.43
0.42
0.41
0.39
0.37
0.35
0.35
0.35
0.35
0.35
0.33
0.31
0.27
0.24
0.21
0.19
0.18
0.19
0.19
0.19
0.19
0.18
0.16
0.15
0.13
0.13
0.14
0.15
0.17
0.18
0.18
0.17
0.15
0.13
0.11
0.10
0.10
0.10
0.08
0.06
0.03

--
Roger Chapman