Arctic warming is still very much in the news and there is on-going concern that this may cause accelerated melting of permafrost, release of even more CO2 and methane and a form of runaway warming. A little known “fact” is that many parts of the Arctic were just as warm around 1940 as they are today. This is a theme I will return to shortly with a few more comprehensive data sets. In this short post I simply want to take another look at the two records close to Yamal – Ostrov Dikson and Salehard – that I mentioned in my recent post on the Yamal “vent”.
Figure 1 GHCN V2 “raw” in blue and GHCN v3 “adjusted” records in red for Ostrov Dikson, near Yamal, Arctic Russia. Scales offset by 3˚C to facilitate comparison. Can you spot the forgery from the Da Vinci?
For the uninitiated, GHCN stands for Global Historic Climatology Network a part of NOAA in the USA and charged with curating climatic records. GHCN V2 are often referred to as the “raw” records but have in fact been subjected to some adjustments. GHCN V3 homogenised records have been subjected locally to very significant adjustments aimed supposedly at removing non-climatic artefacts from the data, such as moving the recording site or the time of day recordings were made. The V1 actual raw records are evidently not available on line but are rumoured to be circulating on a CD. The story so far is that within any region, some records are warmed and some are cooled with a close to zero net effect.
Figure 2 Running regressions through the raw and adjusted records we see that a gradual cooling trend is turned into a significant warming trend. It needs to be noted that 1943 and 1945 were significantly warmer than the present day, a “fact” removed by the adjustments made to the records. Temperature scales are offset by 3˚C to enable comparison.
Figure 3 So how is this magic achieved? Quite simply by adding 1.6˚C to the raw record from 1957. This is one of the more blatant and significant versions of data adjustment I’ve seen.
Figure 4 In Salehard its even more difficult to spot the forgery from the Da Vinci. A close inspection shows that in the raw record, 1942 ties for warmest year. In the adjusted record 1995 is the clear winner.
Figure 5 A more subtle approach to homogenisation is applied in Salehard with gradual but progressively more cooling added to the warm leg of the raw data in exact decimal fraction increments.
Figure 6 The average of 21 GHCN V2 raw records for E Siberia has the same form as Ostrov Dikson and Salehard with characteristic warming leg, cooling leg and a recent warming leg.
Are these adjustments justified? As far as I have seen so far, this form of record is common in the Arctic. In fact it seems to be characteristic of the Arctic dominating in E Siberia (See Figure 6) and in Northern Scandinavia. So what we are left with is a methane vent that probably isn’t on Yamal that formed in response to warming manufactured by a GHCN bot.