In this post the raw temperature records for 7 Icelandic climate stations as reported by the Iceland Meteorological Office (IMO) are compared with the equivalent records archived by GHCN as V2, presumed previously to be raw temperature records. What should have been a straight forward exercise is in fact a total mess. Out of a possible total of 1056 annual records (8 locations times 132 years):
- 220 records exist in V2 that do not have an IMO equivalent*
- 104 records that exist in the IMO archive do not exist in V2
- 182 IMO records are found to be exactly the same as V2**
- 334 V2 records have been changed from the IMO raw data
- 216 records do not exist in either archive, i.e. no data
* This includes the whole of the V2 Vestmannaeyja record that we cannot find on the IMO data base
** For 7 locations there are strings of data that are identical in IMO and V2 archives suggesting the latter did indeed start life as raw IMO data.
At face value, something appears to have gone catastrophically wrong with the GHCN V2 archive which cannot be viewed as raw data in its current form. One possibility is that the IMO provided records to GHCN that do not match their current archive and we are awaiting IMO to clarify this point. Alternatively, we may have made some mistakes in accessing the raw IMO records.
However, despite what appears to be mass deletion, addition and changing of records by GHCN or NASA GISS the net result is minimal. It is hard to spot the differences between the IMO and GHCN V2 in the mean dT time series plot. As was the case in Central Australia and Southern Africa [2, 3], everything and nothing has been changed. Clarification is required from both the IMO and NOAA / GHCN.
Figure 1 Map showing the location of six of the climate stations discussed in this post.
[Note added 17:30 on 13th March: Ducdorleans has informed me that there is an additional unofficial Iceland temperature series that includes some early unaudited data for Akureyri and Reykjavik and this might explain how GHCN have some early data for these stations that is absent from the IMO official data set.]
[Note added 14:00 on 14th March: I have had a detailed response from the IMO that included a file with data for Vestmannaeyja, 1877 to 1995. The response details some of the many challenges involved in archiving records and also highlights the possibility for misunderstanding through inconsistent use of nomenclature. For example, what exactly are “raw records” and what exactly are “official records”. At present it suffices to say that data reported by GHCN for Akureyri, Reykjavik and Vestmannaeyja does exist (in green on my Figure 2), but evidently not archived on the IMO web site.]