Record Arctic Warmth – in 1937

In this post I take a look at the GHCN V2 records for 32 stations in the Arctic and sub-Arctic areas of Norway, Sweden, Finland and the adjacent part of Russia (Figure 3). The data throw up some surprising results.

• Despite coming from 4 different countries, these are among the most congruous time temperature series I’ve seen, i.e. the temperatures go up and down together across the region, with quite substantial oscillations of ±2˚C (Figure 1).
• Averaging the data reveals that 1937 (and 1938) were the warmest years in this area (Figure 7).
• At the end of the Little Ice Age, 1881, 1888, 1893 and 1902 were anomalous cold years. This cold start to the time-temperature series creates the inevitability that a regression through the data will have a positive slope (Figure 3). Had the thermometers not been deployed until 1920, then the regression would have been virtually flat (Figure 9).
• Once again we have essentially a flat rangebound series with three main legs to the data. Warming until 1938, cooling until 1968 and then warming to the present. It was just as warm in this part of the Arctic and sub-Arctic in the 1930s as it is today.
• The structure of the data is similar to the North Atlantic Oscillation suggesting that this climatic feature has played a role in modulating temperatures in this part of the Arctic. The temperature response is often 1 and sometimes 2 years delayed.
• The structure of the data is also quite similar to a compilation of 21 records centred on Olenek in East Siberia.

Figure 1 dT spaghetti for the 32 station records using the station average as a base for calculating dT. There is a high congruity between all records suggesting that this quite large area that extends to Bjørnøya in the Barents Sea responds as a single congruous climatic zone.

Data and methods

GHCN V2 records as downloaded from the NASA GISS web site have been used. I placed Karasjok (I once dated rocks from the Karasjok Greenstone Belt) at the centre of a GISS search that returned the records shown in Figure 2. The distribution of stations is shown in Figures 3 and 4.

The metANN (DJFMAMJJASON) annual averages were used. The temperatures were converted to anomalies by taking the mean temperature for each station and deducting that mean value from the time-temperature series of each station. It is preferable to use a fixed base period, for example 1963 to 1992 has been used before. For a number of data sets I have compared the fixed base with the station average base and derived very similar results. It is simply easier to use the station average.

The average gradient is determined by summing (averaging) the dT stack for all stations. This too raises methodological questions. 4 stations have long continuous records (1880-2011) and these are plotted separately in Figure 5. A regression has been run through each station and the gradients averaged. This gives an identical result to summing the dT stack and running a regression through that average (Figure 5).

Figure 2 The stations used in this study. There are two sizeable cities – Murmansk and Archangel but neither show signs of urban warming.

Figure 3 Station locations are spread across 4 countries stretching from Bjørnøya (Bear Island) in the Barents Sea to the North to Onega in Russia to the South.

Figure 4 This area has a large number of stations with old records, many of which have unfortunately closed since. In general there is excellent station cover.

Figure 5 There are 4 long continuous records in this group that run unbroken from 1880 to 2011 (Haparanda stops in 2009). The regressions through each record are shown. Averaging those yields +0.98˚C per century identical to the gradient through the sum of the dT stack.

Results

The temperature spaghetti plot (Figure 6) shows how strongly congruous these records are. There is a strong sense of flat records going across the chart and not much sense of warming. Note that some of these stations have average annual temperatures below zero and some above zero.

The conversion to dT spaghetti is shown in Figure 1 which emphasises the flat and strongly congruous nature of these records. The average of the dT stack (Figure 1) is shown in Figure 7.

Figure 6 Temperature spaghetti for 32 Arctic and sub-Arctic stations.

Figure 7 Averaging the dT spaghetti (Figure 1) produces this summary. One feature of these data throughout is quite large inter annual variability with warm years interspersed with cold years and average temperatures varying by as much as 3˚C from warm to cold. There are three legs to the data. Warming to 1937. Cooling to about 1968 followed by warming to the present day with a quasi 80 year cycle. One surprising result is that 1937 and 1938 were the warmest years by some margin. 

Figure 8 Comparing dT with the North Atlantic Oscillation Index reveals a fair degree of co-variance although the correlation is far from perfect. The frequency and style of oscillation are very similar. Quite often the temperature and NAO index are offset with temperature lagging the NAO by one year and sometimes two years. On other occasions there is very tight alignment, for example 1941/42 but even that may be one year displaced. A regression through the NAO index has negative gradient and so this cannot be used to explain the quasi 80 year structure.

Figure 9 Starting the regression in 1920 produces a near flat trend. There has been no warming in this part of the Arctic for 95 years.

Figure 10 The overall pattern seen in Northern Scandinavia is very similar to that seen in east Siberia. The E Siberian records are centred on Olenek, 2980 km east of Murmansk. The climatic regime in E Siberia is more harsh with larger seasonal swings. It is both interesting and surprising that the patterns are so similar.

Discussion

Arctic warming and the “disappearance of sea ice” seems very much to be in the news. It is difficult to understand the basis for this panic based on these data or the data from Olenek and Iceland. Sure, there has been some warming since 1966, but this seems little different to the warming that took place in the period 1902 to 1937/38.

Is there evidence for Arctic warming elsewhere? Looking to the north there are a couple of stations on Svalbard. The Svalbard airport record begins in 1977 and so only catches the recent warming leg seen in all the other records. Taking this record in isolation presents a false picture. Also on Svalbrad is Isfjord Radio. But that record stops in 1980 and therefore misses any recent warming. Going across the Atlantic to NE Greenland there is a useless record at a military base called Nord Ads. It begins in 1952 and also misses the warm 1930s that provide context.

Svalbard Airport
Isfjord Radio
Nord Ads

If we go to Iceland, using the V2 records we see a similar picture to N Scandinavia with equally warm temperatures in the 1930s. In Iceland, V3 homogenised records create an image of warming created in the mind of the homogenisation bot.