(GREENLAND, ICELAND, NORWAY, FINLAND)
SCOPE
There have been many reports, and much evidence, that the temperature in the Arctic has in recent decades been increasing dramatically at a rate higher than in other regions of the world. Increases of up to 5°C have occurred in the past 50 years.
This Note examines the temperature records at nine long-term stations in Greenland, Iceland, Norway and Finland. All of the stations are located at latitudes of at least 60°N (the latitude of Oslo) and have data records of over a century.
Separate Notes have been prepared for other arctic and sub-arctic regions of the world – see Links below.
DATA
The earliest record is at Vardo in northern Norway where data have been observed since 1829. The number of complete years of data ranged from 86 years at Jan Mayen to 179 years at Vardo.
Except for Svalbard, all of the data used were downloaded from the website of the Royal Netherlands Meteorological Institute (KNMI).
The data used for Svalbard is a composite record derived by the Norwegian Meteorological Institute of data observed at 12 locations on Spitsbergen Island and the adjacent Edgeoya Island. Particularly used were the data from Green Harbour (1911-1930), Isfjord Radio (1934-1976), Longyearbyen (1911-1977) and Longyearbyen Airport (1977-2019). The composite record was adjusted to represent the temperature at Longyearbyen (Svalbard) Airport.
Apart from Sodankyla all of the nine stations analysed are located at coastal locations.
METHODOLOGY
For each of the nine stations plots were made of the annual mean temperatures and also of the summer and winter mean temperatures. For the purpose of this analysis “summer” was defined as June-August and “winter” as December-February (even though the actual winter season can extend over longer periods).
No trendlines were fitted to the plots as such actions are highly subjective. Instead linear regression lines are shown; these are NOT trendlines but are added so as to provide a baseline for the viewer. There has been a world-wide overall increase in annual mean temperatures over the past century (and beyond) so this enables the viewer to observe the variation from the mean trend at individual stations.
RESULTS
There are strong similarities in the annual mean temperature trends at all nine stations. Cyclical trends are evident with peaks around the 1930s and 2010s and a trough in the 1960s. Since about 1970 the temperature trend has been increasing at all stations. A somewhat similar increasing trend occurred between about 1900 and 1950, with a consistent decrease in temperature between about 1950 and 1970. An example of this is shown at Bodo, with linear regression lines plotted for the two 50-year periods, 1900-1949 and 1970-2019:
It is seen that the period of increasing temperature between 1970 and 2019 is a repeat of a similar increase between 1900 and 1949. This comparison applies to all of the stations (except Jan Mayen where records commenced in only 1921). So the temperature increase over the period 1970-2019 period is not unique!
The linear regression slopes for the total records, 1900-1949 and 1970-2019 are:
It is seen that, for the full period of records, the linear trend slope at Svalbard (+0.32°C/decade) are three to five times that at the other eight stations. For the period 1970-2019 the linear trend slope at Svalbard is about double that at the other eight stations.
The trends of the Summer and Winter temperatures are similar to the annual trends, but generally with greater linear trend slopes in winter than in summer. The linear trend slope for the summer (Jun-Aug) period varied from 0.01 to 0.13°C/decade, The linear trend slope for the winter (Dec-Feb) period varied from 0.05 to 0.41°C/decade.
PLOTS FOR INDIVIDUAL STATIONS
NUUK
[ There are much missing data since 2002. The recent temperatures are less than were recorded in the 1920s and 1930s. ]
TASLILAQ
[ There are much missing data since 1998. The recent temperatures are similar to those recorded in the 1920s and 1930s. ]
STYKKISHOLMUR
[ There are much missing data since 2000. The recent temperatures are similar to those recorded in the 1930s. There is very little variation in the temperature trend prior to about 1925. ]
AKUREYRI
[ There is a pronounced period of higher temperatures in the 1930s and 1940s. These temperatures were warmer than in recent years. ]
JAN MAYEN
[ Records commenced only in 1921. There are many missing data in the 1960s. ]
SVALBARD
[ This is an amalgamation of data from several stations. There was a well-defined decrease in temperatures in the 1950s and 1960s. The recent temperatures are warmer than in the 1920s to the 1940s. ]
VARDO
[ This is a very long record – since 1829. The recent temperatures are warmer than in the 1920s and 1930s. ]
BODO
[ The recent temperatures are similar to those recorded in the 1920s and 1930s. ]
SODANKYLA
[ This is an inland station. Recent temperatures are similar to those recorded in the 1920s to 1940s. ]
CONCLUSIONS AND COMMENTS
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Very similar temperature trend patterns occurred at all nine stations.
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At all stations long periods of rising temperatures occurred between about 1900-1950 and 1970-2019, with decreasing temperatures between about 1950-1969. The warming period between about 1970 and 2019 is not unique.
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At only three of the nine stations (Jan Mayen, Svalbard and Vardo) were the recent temperatures (since about 2000) markedly warmer than in earlier decades around 1920-1940. At two stations (Nuuk and Akureyri) the recent temperatures were less than those around the 1930s.
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The trends of the summer and winter temperatures were similar to the annual trends.
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The linear rate of temperature increase at Svalbard, averaged over the full period of records, was three to five times the rate at the other eight stations.
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The temperature trends show a cyclical pattern with periods of around 80 years. This effect is more pronounced at some stations (eg Akureyri) than at other stations (eg Bodo).
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The linear trend slope over the period 1970-2019 varies between three and seven times the linear trend slope over the full period of records. It is therefore misleading to base trend estimates only on records over a shorter period (such as since the 1960s or 1970s).
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Despite the above comments it is appreciated that many locations in the arctic and sub-arctic have experienced sustained warming temperatures over the past 50 years. This warming has had a significant effect on the local environment and population.
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If history repeats itself (which is very hard to predict!) a correction period of decreasing temperatures, similar to that of 1950-1970, is possible in the near future!
REFERENCES AND LINKS
Do you have any comments on the above? brigun (at) westnet.com.au
THE AUTHOR
This article was written by Brian Gunter Narooma, NSW, Australia. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow of data for the planning of major water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Australian Bureau of Meteorology.
Published by
Brian Gunter
Retired civil engineer.
Particularly interested in climate trends.
View all posts by Brian Gunter
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