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The Official Iceland Temperature Series

Paul Homewood, Not A Lot Of People Know That

Now that GHCN and GISS have managed to emasculate the Icelandic temperature record, it is time to present the official version. With special thanks to Trausti Jonsson,  Senior Meteorologist with the Iceland Met Office.


Now that GHCN and GISS have managed to emasculate the Icelandic temperature record, it is time to present the official version.

The Iceland Met Office, (IMO), have kept meticulous temperature records since the 19thC, including station metadata as well as just the temperature data. In fact the Icelanders took their climate very seriously in those early days, unsurprisingly since they are so vulnerable to climate shifts. There is an interesting overview of the work of people such as Thoroddsen and Nansen in the early 20thC here.

In particular, they have full records since 1931 for seven stations.

It needs to be emphasised that these are not raw temperatures, but have been carefully homogenised and adjusted where necessary, to account for station moves and equipment changes.

Trausti, who has done much of the work himself over the last three decades, explains:

I would again like to make the point that there are two distinct types of adjustments:

1. An absolutely necessary recalculation of the mean because of changes in the observing hours or new information regarding the diurnal cycle of the tempearture. For Reykjavík this mainly applies to the period before 1924.

2. Adjustments for relocations. In this case these are mainly based on comparative measurements made before the last relocation in 1973 and supported by comparisons with stations in the vicinity. Most of these are really cosmetic (only 0.1 or 0.2 deg C). There is a rather large adjustment during the 1931 to 1945 period (- 0.4 deg C, see my blog on the matter – you should read it again). 

I am not very comfortable with this large adjustment – it is supposed to be constant throughout the year, but it should probably be seasonally dependent. The location of the station was very bad (on a balcony/rooftop).

I must emphazise that an adjustment on the top of an adjustment is a very bad idea. [GISS – please note!]

One must be very open about the data – and the adjustments used.

It is also important to realise that the adjustment/homogenizing process is always a compromise – information is always lost during the process.

This, of course, is exactly how the procedure should operate.

The homogenised data is available at the IMO website here.

We can take a look a three of the sites, regarded by the IMO as long running and representative.




 Across all three sites, we find temperatures in the 1930’s and 40’s up around where they have been during the current warm period. The main difference, however, is how persistent this recent warm weather has been, compared to the 1940’s, where there were some extreme year-on year changes. As Trausti comments “there has not been a single cold year since 1995.”

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