climate gate email 1 of 1000

From: "Tim Osborn"

To: I.Harris@uea.ac.uk

Subject: cruts tmp to 2008

Date: Fri, 10 Jul 2009 00:19:58 +0100 (BST)

Reply-to: t.osborn@uea.ac.uk

Cc: "tim Osborn"

Hi Harry,

finally had time to take a look at the latest cruts3 run through to 2008

for tmp, picked up from /cru/cruts/

Two PDFs showing seasonal national means are attached.

Look at ...2008a_vs_2008b.pdf first. Black is your previous update to

2008, pink is the latest one. Many very similar, some small differences

(presumably due to outlier 3/4 SD removal... note that as these are

national/seasonal means, outliers might be quite large, yet only show up

small in the means if many other stations contribute).

page 4. The hot spike in Guatemala SON has been removed in the new

version. That looks much better.

page 6 & page 9: the hot spikes in France, Italy and Austria in JJA in

2003 have been reduce slightly too. Not sure if this is right or not,

could ask Phil what he thinks. Could Jul & Aug 2003 have been so hot that

some observations validly did exceed the +3SD outlier check? Or do you

use a +4SD check for TMP? Anyway, this is one to ask Phil about.

There are various other erroneous hot spikes that have now been correctly

removed, I won't list them all here.

However, there are some cold spikes in both previous and latest 2008

updates... see e.g. Mali SON on page 12. Have you turned on only outlier

checking for +3SD, and not for -3SD? Some wrong-looking cold spikes are

still present.

Now look at ...2005_vs_2008b.pdf. Black is last years CRUTS3 through to

2005 (I know the files went to mid 2006, but I stopped at last complete

year). Note this isn't CRUTS2.1! :-) Pink is again the newest version of

the update to 2008.

There are some early 20th century differences that I'm not too bothered

about, though it would be nice to know why they arise. One concern is

that the mean level is different between the versions... see e.g. JJA for

various countries on pages 7 and 8. Seems to be a constant offset. It's

too big to be a simple rounding error in my calculations (I may have

changed from 1 dec. place to 2 dec. place, but some differences are about

0.5 deg C), and these are absolute values so there's no dependency on any

anomalisation/reference period meaning as I'm not doing any.

Intriguing. Perhaps some normals have change in some regions/seasons?

So:

(1) hot spikes have been corrected.

(2) cold spikes still there.

(3) some odd differences in mean level.

Progress!

Tim

--

Dr. Tim Osborn

RCUK Academic Fellow

Climatic Research Unit

School of Environmental Sciences

University of East Anglia

Norwich NR4 7TJ, UK

www.cru.uea.ac.uk/~timo/

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