Cooling The Past In Iceland

By Paul Homewood

Figure 1. Annual temperature in Stykkishólmur 1798 to 2007. Note that the values prior to 1845 are interpolated from observations at other stations. The confidence is very low for the years before 1830 and the values are preliminary and should not be referenced. Work on quality improvement is ongoing. A few warm and cold years are highlighted.

Figure 2. 7-year running means of temperature at three locations in Iceland, Reykjavík (red trace)), Stykkishólmur (blue trace) og Akureyri (green trace). Kuldakast = cold period. The first of the marked periods was the coldest one in the north (Akureyri), the second one was the coldest in Reykjavík.

http://en.vedur.is/climatology/articles/nr/1213

The above charts were published by the Icelandic Met Office back in 2008, in an article “Past temperature conditions in Iceland”. They show annual temperature trends at three of the longest running stations in Iceland, and the report comments:

The 20th century warm period that started in the 1920s ended very abruptly in 1965. It can be divided into three sub-periods, a very warm one to 1942, a colder interval during 1943 to 1952, but it was decisively warm during 1953 to 1964.

The cold period 1965 to 1995 also included a few sub-periods. The so called "sea ice years" 1965 to 1971, a slightly warmer period 1972 till 1978, a very cold interval during 1979 to 1986, but thereafter it became gradually warmer, the last cold year in the sequence being 1995. Since then it has been warm, the warmth culminating in 2002 to 2003. Generally the description above refers to the whole country, but there are slightly diverging details, depending on the source of the cold air.

It is noticeable that temperatures in the years up to 2007, and particularly the high point of 2003, were only slightly higher than the the warm period around 1940, and later in the 1950’s. Also, at Stykkisholmur, the gradual warming trend has been pretty consistent since 1800, with no sign of anything unusual lately.

Until 2011, the data used by GHCN & GISS reflected this pattern.

http://data.giss.nasa.gov/cgi-bin/gistemp/show_station.cgi?id=620040300000&dt=1&ds=2

However, in November of that year, GHCN brought out a new version, V3.1, which introduced a new set of homogeneity adjustments, and, as a result, Reykjavik’s temperature history turned into this.

http://data.giss.nasa.gov/cgi-bin/gistemp/show_station.cgi?id=620040300000&dt=1&ds=14

The effect of the adjustments can be seen on the GHCN station images below. (Check right hand column – Top graph is unadjusted, middle adjusted and bottom shows the adjustment, blue for adjusting down, red up)

ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v3/products/stnplots/6/62004030000.gif

Below is a blown up image for Reykjavik. Note how how the middle, adjusted graph has eliminated the sea ice years of 1965-71. It does this adjusting down temperatures prior to 1965, which also has the added effect of flattening the temperature spike around 1940, thus making recent years appear much warmer by comparison.

And the same with Stykkisholmur and Akureyri.

ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v3/products/stnplots/6/62004013000.gif

ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v3/products/stnplots/6/62004063000.gif

In the case of Reykjavik and Akureyri the effect of the adjustments is to increase the warming trend since 1940 by a full degree or more.

The homogeneity adjustment is to designed to spot and correct for abrupt shifts in the temperature record, due to non climatic factors such as relocations. In this case, it has clearly mistaken a genuine climatic shift as something else, and as a result altered out of recognition Iceland’s whole historic record.

GHCN are fully aware of this error, as I have pointed it out to them on several occasions. Each time I have been promised it would be checked out and either corrected or explained, and each time, despite chasing several times, nothing happens.

Two conclusions are abundantly clear:

1) There is no justification for the adjustments.

2) GHCN have no desire to put matters to right or admit the errors, not least because it would open up a whole can of worms, and shed doubt on other adjustments elsewhere.

The sea ice years were very real and many scientific papers have been written about them, see here. The cold also had a serious impact on Iceland’s economy, as Trausti Jonsson, the senior meteorologist at the Iceland Met Office attests:

“In 1965 there was a real and very sudden climatic change in Iceland (deterioration). It was larger in the north than in the south and affected both the agriculture and fishing – and therefore also the whole of society with soaring unemployment rates and a 50% devaluation of the local currency. It is very sad if this significant climatic change is being interpreted as an observation error and adjusted out of existence.

I have been working for more than 25 years in the field of historical climatology and have been guilty of eager overadjustments in the past as well as other data handling crimes. But as I have lived through these sudden large climatic shifts I know that they are very real.”

But apparently GHCN knows better.