The longest temperature record in the Faroe Islands is from a station at Thorshavn. It has nearly 1800 months of data, but no other temperature record in the islands has more than 435 months of data. In fact only another two (at Vagar and Akraberg) have more than 120 months of data (see here for a list). This means that the temperature record for the Faroe Islands is heavily dependent on the Thorshavn data with the other two stations only affecting the mean temperatures after 1980.
The result is the time series for the mean temperature anomaly (MTA) shown in Fig. 121.1 below. What is striking is that the general form of the five-year moving average (yellow curve) is very similar to those for both Greenland (see Fig. 119.1 in Post 119) and Iceland (see Post 120.1 in Post 120). Temperatures declined from 1930 until 1990 and then rebounded. In all three cases the temperatures today are no higher than in the 1930s but the amount of cooling from 1930-1990 is different, being highest for Greenland and least for the Faroe Islands. This is not a surprise, though, as it is well known that climates that are more extreme (i.e. Greenland) experience larger temperature fluctuations than are seen in more temperate climes (i.e. the Faroe Islands).
Fig. 121.1: The mean temperature change for the Faroe Islands since 1920 relative to the 1981-2010 monthly averages. The best fit is applied to the monthly mean data from 1931 to 2010 and has a negative gradient of -0.40 ± 0.15 °C per century.
In order to quantify the changes to the climate of the Faroe Islands the temperature anomalies for the three longest station records were averaged. This was done using the usual method as outlined in Post 47 and involved first calculating the temperature anomaly each month for each station, and then averaging those anomalies to determine the mean temperature anomaly (MTA) for the region.
The process of determining the MTA in Fig. 121.1 involved first determining the monthly reference temperatures (MRTs) for each station using a set reference period, in this case from 1981 to 2010, and then subtracting the MRTs from the raw temperature data to deliver the anomalies. The total number of stations included in the MTA in Fig. 121.1 each month is indicated in Fig. 121.2 below. The peak in the frequency after 1980 illustrates why the 1981-2010 interval was indeed the most appropriate to use for the MRTs.
Fig. 121.2: The number of station records included each month in the mean temperature anomaly (MTA) trend for the Faroe Islands in Fig. 121.1.
If all the data is considered, the MTA trend for the Faroe Islands will have data extending back to 1867 as shown in Fig. 121.3 below. Much of the data before 1930 indicates that temperatures then, at least for Thorshavn, were cooler than in the 1930s and to day. Again this is similar to the results from Greenland and Iceland, but it is unclear how much of this temperature change is genuine warming of the climate and how much is just the result of natural fluctuations. But the fact that these features are repeated in multiple regions means that they cannot be discounted as being isolated results that are the result of poor measurements.
Fig. 121.3: The mean temperature change for the Faroe Islands since 1860 relative to the 1981-2010 monthly averages. The best fit is applied to the monthly mean data from 1871 to 2010 and has a positive gradient of +0.27 ± 0.07 °C per century.
The locations of the three stations used to determine the MTA in Fig. 121.3 are shown in the map in Fig. 11214 below. The temperature data from all three appear to exhibit modest warming trends, but this is mainly due to the fitting intervals used in each case. Vagar and Akraberg only have data after 1970 where the MTA in Fig. 121.3 is warming. The trend for Thorshavn was for data from 1911-2010, and is therefore biased by the fact that the fitting interval does not extend from peak to peak. This is akin to fitting to a sine wave as I explained with Fig. 4.7 in Post 4. So the positive trend is not real.
Fig. 121.4: The (approximate) locations of the three longest weather station records in the Faroe Islands. Those stations with a high warming trend between 1911 and 2010 are marked in red while those with a cooling or stable trend are marked in blue. Those denoted with squares are long stations with over 1200 months of data, while diamonds denote stations with more than 240 months of data.
If we next consider the change in temperature based on Berkeley Earth (BE) adjusted data we get the MTA data shown in Fig. 121.5 below. This again was determined by averaging each monthly anomaly from the three longest stations in the Faroe Islands. The mean temperature follows a similar trajectory to that of the unadjusted data in Fig. 121.3 with temperatures fluctuating by over 1°C and a large peak occurring around 1930. However the BE adjustments appear to have lowered this peak relative to temperatures in 2010 by over 0.25°C compared to the raw data in Fig. 121.3.
Fig. 121.5: Temperature trends for the Faroe Islands based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1871-2010 and has a positive gradient of +0.61 ± 0.03°C/century.
Comparing the curves in Fig. 121.5 with the published Berkeley Earth (BE) version for the Faroe Islands in Fig. 121.6 below shows that there is good agreement between the two sets of data. However, Berkeley Earth appear to think they can determine the temperature back to 1760 even though there is no data before 1860. Who says climate scientists are pessimists?
Fig. 121.6: The temperature trend for the Faroe Islands since 1750 according to Berkeley Earth.
The differences between the MTA in Fig. 121.3 and the BE versions using adjusted data in Fig. 121.5 can be determined by calculating the difference in the MTA values seen in Fig. 121.3 and Fig. 121.5. The result is shown graphically in Fig. 121.7 below. The blue curve is the difference in MTA values between adjusted (Fig. 121.5) and unadjusted data (Fig. 121.3), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. What is clear is that there is only one significant adjustment. That is a breakpoint adjustment of over 0.25°C made to the Thorshavn data in 1951. The difference between the blue and orange curves in Fig. 121.7 is due to the difference in MRT interval used in Fig. 121.3 and by Berkeley Earth in Fig. 121.5.
Fig. 121.7: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 121.5 after smoothing with a 12-month moving average. The blue curve represents the total BE adjustments including those from homogenization. The linear best fit (red line) to these adjustments for the period 1871-2010 has a positive gradient of +0.330 ± 0.005 °C per century. The orange curve shows the contribution just from breakpoint adjustments.
Summary
According to the raw unadjusted temperature data, the climate of the Faroe Islands has cooled from 1930 to 1980 by about 1°C. It then warmed by a similar but slightly smaller amount until 2005 (see Fig. 121.1).
Over the same period adjusted temperature data from Berkeley Earth appears to show that the climate of the Faroe Islands has warmed by over 0.25°C since 1930 and over 1°C since the 1800s (see Fig. 121.5).
The difference in the raw unadjusted data (Fig. 121.3) and the adjusted data (Fig. 121.5) is mainly due to a single breakpoint adjustment of 0.26°C in 1951.
Any warming trend since 1870 is small (~0.3°C) compared to what look like natural temperature variations (~1°C). The origin of these variations (shown in Fig. 121.3) is uncertain but cannot be the result of greenhouse gas emissions when those emissions were so low compared to today. However, similar patterns are seen in the temperature data of nearby islands of Greenland (Post 119), Iceland (Post 120). and Jan Mayen (from 1920 only), so these features seen in the data before 1930 may be real and representative of synchronous climate variations occurring across the North Atlantic/Arctic region.
Acronyms
BE = Berkeley Earth.
MRT = monthly reference temperature (see Post 47).
MTA = mean temperature anomaly.
Link to list of all stations in the Faroe Islands and their raw data files.
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