Comments on: Russian Bias

By: John Goetz

John Goetz — Sun, 07 Oct 2007 01:36:04 +0000

#74 John V

No, I have not had a chance to start on working on an alternative “CA” combining algorithm. I have had a horrendously busy work and extra-curricular week, so all I have done is get part way into slogging through the rest of the world. Maybe I will be done by next weekend just doing that.

I agree that the only relevant comparison is with a widely accepted algorithm. However, I will be the first to admit I am a horrendously slow programmer. I know what I want to do in my head, but visual basic and excel are woefully underpowered for this task and I am very new to R. I had started looking at modifying Steve’s code to do what you suggest, which I agree to the first order it is a better means of combining records. But I have barely started. I spend 10x the time reading documentation and looking at examples than actual coding. Part of me knows that I won’t be able to respond fast enough to the very good suggestions that will follow. After all, I am sure a number of people will find places where a simple average is inappropriate.

By: John V.

John V. — Sat, 06 Oct 2007 16:38:42 +0000

John Goetz: Have you had any time to consider my suggestion above? The more I think about it, comparing the "Hansen bias" to a "sensible bias" is the only fair comparison.

By: Demesure

Demesure — Tue, 02 Oct 2007 10:47:18 +0000

#70, 71
The data I use for GISS is from the “Download monthly data as text” link under the graphs generated by GISS (dset = 1) (for example here : http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=615072550003&data_set=1&num_neighbors=1 )

Well, I realize that the graphs I made from the GISS monthly data is with a simple annual mean: missing months are not counted instead of being interpolated (see line 34 of the R source code). Hence the 1991 peak in my graphs and not in GISS’ for Bourges and for other towns.

But it visibly leads to a real problem in the GISS datasets: for ALL stations in France, 1991 Jan-Feb-Mar are missing (try Bourges, Marseille, Lyon…). I’m not aware a national disaster struck us and made data disappear for 3 months in 1991 !

And if you look at neighbouring Spain or Italy, it seems that 1991 is also a particular year for GISS since a lot of stations have data ended or started around that date.
Germany, GB, the Nertherlands seem at first glance to be spared from this mysterious 1991 disease.

So the 1 millyuyn $ question is: what was happening in Southern Europe in early 1991 to GISS data ?

By: Demesure

Demesure — Tue, 02 Oct 2007 10:35:45 +0000

#69 Mark I used blended data.
BTW, for Bourges, ECAD blended and non blended are identical.

By: Willis Eschenbach

Willis Eschenbach — Tue, 02 Oct 2007 08:02:18 +0000

Demesure, I can’t recreate your data. I went to the GISS site, and their data for Bourges peaks in 1990 (see Steve’s graph above), while yours peaks in 1991 … what’s up with that?

By: Steve McIntyre

Steve McIntyre — Mon, 01 Oct 2007 23:42:40 +0000

Demesure, I'll do a post on Bourges, which will be a good way of drawing attention to the ECAD data set. HOwever, I can't tie your representation of GISS back to GISS data and this needs to be sorted out first. Also you need to specify which GISS version you're using. Below is dset=1.

By: MarkR

MarkR — Mon, 01 Oct 2007 20:42:19 +0000

Demesure.

Both blended and non-blended ECA series are available for download. Blended series are series that are near-complete by infilling from nearby stations. They are also updated using synoptical messages. Only these blended series are further analysed in ECA&D.

http://eca.knmi.nl./dailydata/index.php

In this procedure the gaps in a daily series are also infilled with observations from nearby stations, provided that they are within 25km distance and that height differences are less than 50m.

http://eca.knmi.nl./FAQ/index.php#3

Apparently one can get “blended”, or “unblended”. Interesting that their criteria for infill are a lot closer to home than GISS.

By: Demesure

Demesure — Mon, 01 Oct 2007 20:20:50 +0000

Willis, I got it now. For France, most data from the GISS don't have January, feb, and Mars for 1991 (see .TXT files retrieved from the GISS site). Remove cold months and you make the 1991 temperature jump. Voila Waldo ! Don't know who of GHCN or GISS fathered him but he's here.

By: Demesure

Demesure — Mon, 01 Oct 2007 19:56:17 +0000

OT again, to reply to Willis #49
The link given by Steve to Bourges (GHCN V2) shows missing months for 1990-91.
That may explain the huge difference between blue and red curves above.
Some months lacking is ridiculous for such recent data : on the ECAD database, you have even daily temperatures !
I’ll check other French stations.

By: Demesure

Demesure — Mon, 01 Oct 2007 19:40:02 +0000

#57. Oh yes, sorry for the OT and for not giving the link to my data. Steve, it seems data of your link to KNMI (GHCN V2, black curve in graph below) is still different from data I retrieve from "KNMI" at this link : http://eca.knmi.nl./dailydata/index.php . In fact, it's the "European Climate Assessment Dataset". I found it thanks to a link on the KNMI site so I called it KNMI but I shouldn't because it's misleading. Now I've rename it ECAD (blue curve). So bad for not being here, maybe I've missed something important. I must confess, all thoses GMT (genetically modified temperatures) are a real nightmare for me and I'd love to have a "Hansen in France" thread to get things clearer.