Now that I’ve produced a series of colour coded maps showing the warming/cooling trends in the NOAA/GISS GHCN data for three distinct time periods i.e. 1880 to 1939, 1940 to 1969 and 1970 to 2010 (as well as for the whole 1880 to 2010 period), I’ve noticed that a number people commenting on the ‘Mapping global warming’ thread here are unaware of the NOAA/GISS station ‘drop out’ issue and how it may affect the warming/cooling trends.
The primary purpose of this new thread is to show charts of the number (i.e. count) of stations by year in the NOAA (and so therefore more or less GISS also) GHCN raw and adjusted datasets.
Because I’ve further broken down the station counts by ‘WMO Region’ and still further by Country for each of the separate charts for each WMO Region, I’ve chosen to display the charts as both ‘stacked’ area charts and ‘unstacked’ area charts.Because there are many countries in any given WMO Region, I’ve also chosen to show separate series for the ‘Top 10’ countries in a region and have lumped the remainder into an ‘All Others’ category. To see a much larger readable version of a chart just click on the appropriate chart.
I’ll now present each set of charts in turn, starting with the overall raw/adjusted charts first, and followed by some observations that are evident within the charts. Note that in each case the ‘No. of stations’ is the count of the no. of stations that have recorded temperature data available in the GHCN dataset in that given year.
Raw data – No. of stations by year for All WMO Regions
Figures 1 and 2 above show for how many stations there is raw temperature data available in the NOAA GHCN raw dataset (the v2.mean file) for each year from 1880 to 2009. The station count data has been broken down further to show the station counts for each WMO Region as a separate series. As can be seen from the charts, there are relatively few (less than 500) stations that have raw temperature data prior to 1880. From 1880 onwards there is a more or less linear increase in the no. of reporting stations (i.e. stations that have raw data) from 1880 to about 1950 when the number reaches a little over 3300. After this point, within the space of four years, there is a sudden expansion in the number to over 4500, which then reaches a peak of 5348 stations in 1966. Its worth mentioning that there are 7250 records in the GHCN station inventory file (v2.temperature.inv) some of which are for ‘Ships’ but it is clear from this peak count that there isn’t raw temperature data available in the GHCN v2.mean file for all the stations listed in the NOAA GHCN station inventory file.
After peaking in 1966 the total raw data station count then declines in a more or less linear fashion to about 3750 in 1989. Over the next couple of years there is a sudden ‘drop out’ of stations from the total station count to about 1900 in 1992. Figure 2 shows that this ‘drop out’ is for non-North American stations i..e Asian, European and South West Pacific (Australian) stations. Why the sudden preciptious drop in the station count post 1989/1990? Further fine details for this ‘drop out’ can be seen in the later charts for the individual WMO regions (see Figures 8,10 and 12). After 1992 there is a more or less linear decline in the raw data station count to about 1630 stations in 2005. There is then a further sudden inexplicale ‘drop out’ to about 960 stations in 2006 with in 2009 the total station count reduced to a mere 840 stations. What on earth is going on here? What caused the sudden increase in the number of reporting stations around 1950 and what caused the equally precipitous ‘drop out’ of many of these stations around 1989/1990?
Adjusted data – No. of stations by year for All WMO Regions
As can be seen from Figures 3 and 4 above, the general shape of the total adjusted data station count is very similar to that for the raw data station counts in Figures 1 and 2. There are however some interesting further observations to be noted. If you look at Figure 4 relative to Figure 2, you can see that, despite the addition of a significant number of raw data stations in North America (primarily the US) in about 1950, there is no corresponding step increase in the station count for the adjusted stations. In particular note the station ‘drop out’ post 1989/1990. After 1990 almost all the North American (US and Canadian) adjusted data stations have ‘dopped out’. Also if you look at Figure 3 , in 2006, the number of adjusted stations plummets to less than 190 and of those only 27 are North American (US) stations; in 2008 the adjusted station count reaches as low as 55 (10 North American, 8 Asian, 2 European and 35 South West Pacific (Australia).
For anyone interested, the peak value in the number of adjusted stations is 4018 in 1966. How on earth is anyone supposed to know what happened to ‘global warming’ in the first decade of the 21st century when the station counts have been reduced to such a ridiculously lower level in the NOAA GHCN dataset? Particularly when you bare in mind that it is this dataset that forms the input to GISTemp that produces all those scary ‘red almost everywhere’ colour contoured anomaly maps?
Raw data stations – North and Central America
The key obsevations in Figures 5 and 6 are, firstly, that the US stations are dominant. Secondly, note the -sudden ‘drop out’ in the Canadian stations post-1989. Down from 407 in 1989 to only 35 in 1991! Why? Have NOAA fallen out with Environment Canada? What happened to the Mexican stations after 1985? Why the precipitous drop in the number of reporting US stations from 842 in 2005 to only 124 in 2006? I think this has something to do with USHCN version 2 but I’m not sure. If so why haven’t NOAA just copied all the raw data they have for the US stations in the USHCNv2 raw dataset into the NOAA GHCN raw dataset? GISS takes the NOAA GHCN raw dataset as its input and replaces all the US stations with data it takes from the USHCNv2 dataset (and other Antarctic station from SCAR). Why therefore doesn’t NOAA save GISS the job of having to read in and merge together data from their two separate datasets?
Raw data stations – Asia
The key obsevation from Figures 7 and 8 is that Chinese stations are the dominant contribution in Asia. It is also clear that are the primary cause of the sudden increase in the number of reporting stations after 1950. Note that the increase in the numbers for Japan and the Russain Federations is much more gradual. All three countries show the ‘precipitous drop out’ of reporting stations around 1989/1990. Why? The Chinese stations in particular drop from a high number of 361 in 1990 to only 14 in 1991. Very odd? In addition to upsetting Environment Canada, has NOAA also broken off diplomatic relations with the Chinese? It looks like diplomatic relations with Mongolia were broken off a little earlier than they were with China as the Mongolian station ‘drop out’ occurs after 1982/83. Meanwhile, having enjoyed good relations with South Korea from 1973 when the number of reporting stations increased to over 60, sadly after 1993, the South Koreans appear to have also fallen out with NOAA with the numbers dropping to only 10 in the subsequent years.
Raw data stations – Europe
Now who said “Turkeys never vote for Christmas”? Well according to Figures 10 and 11 the population of Turkish thermometers was thriving between 1961 and 1990. It looks like there was a dramatic change in Turkish voting patterns post 1990 – the Turkey thermometers clearly opted to vote for Christmas and as a consequence their population was culled dramatically with about only 10% of their population survivng post 1990. The post-1950 step increase in the number of reporting stations is evident for most of the European countries, particularly Poland, Germany, Italy and France. It seems the French (according to NOAA) didn’t care very much about measuring temperature prior to 1950.. Clearly everyone in Europe decided that measuring temperature was less important after 1989/1990. Did the EU bureaucrats decide to introduce a tax on measuring temperature at about that time?
Raw data stations – South West Pacific
Well the WMO obviously doesn’t like to upset people who live in the South West Pacific by just referring to it as Australia! But for a small and brief contribution from the Philippine and Indonesian stations from 1950 to 1975, the whole region is clearly dominated by the Australian stations with just a smidgeon of help from New Zealand and Malaysia. Quite why there is the extreme preciptitous (but now all too familar) ‘drop out’ after 1991/2 I don’t know. There were ZERO reporting Australian stations in 1994 according to NOAA by the way! Why?
Raw data stations – Africa
There’s not that much to see in Africa really. With the possible exception of South Africa, no one country dominates. What is evident, as with most of the other WMO regions, is the step increase in the number of reporting stations in what seems like most if not all of the African countries in around 1950. There appear to be two stages to the station ‘drop outs’ . The familarly 1989/1990 ‘drop out’ appears to be preceded by a further ‘drop out’ period at around 1978/79. There’s also an observable doubling in the number of reporting South African stations from 1961 onwards until the 1989/1990 ‘drop out’. From about 2002/3 almost 50% of the contribution towards the African station count comes from only one country – Algeria. What happened to the South African stations?