In its land surface temperature calculations, NASA GISS is little more than a distributor for NOAA GHCN. As Gavin Schmidt explained, they spend no more than 0.25 man-years on this product, which permits negligible (if any) quality control. Although there are 7280 stations in the GHCN network, only a fraction of these occur as up-to-date records in GHCN (or their distributor), even from countries where up-ro-date information is easy to locate (e.g. Canada, New Zealand). I’ve discussed this bizarre failure to update station data on many occasions in the past.
Aside from seemingly poor practice, a further issue for me and others is whether some kind of bias has been introduced into the system by the discontinuity. Assessing this potential bias is not a small job and one that NOAA and NASA should obviously have done long ago and existing literature does not do so.
An obstacle to assessing such a bias has been the lack of any clear description of the update program. In my recent review of the data, I noticed a couple of scraps of information and have now constructed what I believe to be a reasonable accurate inventory of the stations that are included in the GHCN update program.
Peterson et al (BAMS 1997) reported the following update procedure:
Of the 31 sources, we are able to perform regular monthly updates with only three of them (Fig. 5). These are 1) the U.S. HCN, 1221 high quality, long-term, mostly rural stations in the United States; 2) a 371-station subset of the U.S. First Order station network (mostly airport stations in the United States and U.S. territories such as the Marshall and Caroline Islands in the western Pacific); and 3) 1502 Monthly Climatic Data for the World stations (subset of those stations around the world that report CLIMAT monthly code over the Global Telecommunications System and/or mail reports to NCDC). Other stations will be updated or added to GHCN when additional data become available, but this will be on a highly irregular basis.
When they said that the “other stations” would be updated on a “highly irregular basis”, they were not joking. In the 11 subsequent years, as far as I can tell, there have been no such updates. We’ve already collated information on the 1221 USHCN sites, but the GHCN website unfortunately doesn’t provide any lists of either the 1502 MCDW stations or 371 First Order stations.
Last fall, included in the NASA GISS archive were two tables named “mcdw.tbl” and “sod.tbl” (insert urls). The two tables consisted of columns of id numbers without any descriptors, but the first table had 1522 rows and the second table had 371 rows, matching the information in Peterson et al 1997. When I noticed this, I realized that this was a guide to the stations in the GHCN update program.
Even with this guide, it proved to be a lot of work actually reconciling this information to the inventory of NASA GISS/GHCN station id numbers, as the tables matched to a point, but only to a point. Many numbers in the 2nd column of these tables matched parts of the GHCN station identifications, but there were many sites that were only partial matches. In some cases, the GHCN station seemed to match the number in the first column better than the second column. I got about 95% matched sem-automatically but then had a bunch of left over numbers for which I sought matches in a variety of ways. I inserted oddball id numbers at this website (http://weather.gladstonefamily.net/site/42599 ) and got names; then I checked partial name matches in my GHCN station inventories to see if the id number resembled any of the numbers in the two tables.
I got close enough that I wanted to finish the enterprise and eventually wasted a lot of time on it, but I’ve emerged with a plausible list of identifications here: http://data.climateaudit.org/data/station/ghcn/update.dat .
There appears to be a considerable overlap (149 stations) between the two lists (mcdw.tbl and sod.tbl), reducing the total number to 1724 stations. Of the 1724 stations, only 1058 stations have values in 2008.
Although there are no USHCN stations in this part of the network, there are 138 US stations in the non-USHCN update, almost entirely from airports, including large airports like Phoenix, Los Angeles, Houston etc. If you want a list, you can examine them as follows:
The ID numbers in this table tie into the ID numbers in the giss_info collation that I’ve already posted up (which contains some additional GISS information on these sites e.g. altitude, (incorrect) population etc.
Country codes are here and can be read as follows:
NASA GISS makes an effort to adjust for UHI. As noted elsewhere, their procedure in the US is considerably different than their procedure outside the US, as, in the US, the USHCN network, whatever its warts, provides many stations that are not in urban airports. There is scattered information on non-US stations, but this is clearly a major lacuna at present (and I’m sending a copy of this list to Anthony in the hope that this topic will interest him – which seems likely given the interesting recent posts at his site on Verhoyansk in Russia). The Russian (and western China) sites seem like excellent first targets as they have a lot of leverage in overall land-based aggregates.