It is probably not surprising that England has more weather stations of note than Scotland. After all it has about ten times the population and almost twice the area. Yet the difference is not as great as one might imagine. For while Scotland has nine long stations with over 1200 months of data before 2014, England has only a slight advantage with ten stations. For medium stations with over 480 months of data the difference is greater with England having 55 compared to 13 in Scotland. There is, however, more clustering of stations in England as the map in Fig. 143.1 below shows.
Fig. 143.1: The (approximate) locations of the 65 longest weather station records in England. 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 medium stations with more than 480 months of data.
In order to quantify the changes to the climate of England the temperature anomalies for all stations with over 480 months of data before 2014 were determined and 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 relative to its monthly reference temperature (MRT), and then averaging those anomalies to determine the mean temperature anomaly (MTA) for the whole country for each month. The MRTs for England were calculated using the same 30-year period as for the UK in Post 141, namely from 1956-1985.
The resulting MTA is shown as a time series in Fig. 143.2 below and clearly shows that temperatures rose slightly over 150 years up until 1975 before increasing more rapidly thereafter. In this respect the MTA data for England more resembles that of Great Britain (see Fig. 141.2 in Post 141) than it does that of Scotland (see Fig. 142.2 in Post 142) or Ireland (see Fig. 140.2 in Post 140).
Fig. 143.2: The mean temperature change for England since 1760 relative to the 1956-1985 monthly averages. The best fit is applied to the monthly mean data from 1826 to 1975 and has a positive gradient of +0.35 ± 0.08 °C per century.
The temperature trend for England was calculated using the usual method as outlined in Post 47 and involved first calculating the temperature anomaly each month for each station relative to its monthly reference temperature (MRT), and then averaging those anomalies to determine the mean temperature anomaly (MTA) for the whole country for each month. The graph in Fig. 143.3 below indicates how many stations were available each month in order to contribute to that month's MTA.
The MRTs for England were calculated using the same 30-year period as for the UK in Post 141, namely from 1956-1985. The resulting MTA is shown as a time series in Fig. 143.2 above and clearly shows that temperatures were slowly increasing for over 150 years up until 1975. Then at some point in the 1980s (probably in 1988) the mean temperature appears to increase abruptly by about 1°C. This is a phenomenon that has been seen in many other temperature trends across Europe.
Fig. 143.3: The number of station records included each month in the mean temperature anomaly (MTA) trend for England in Fig. 143.2.
If we next consider the change in temperature based on Berkeley Earth (BE) adjusted data we get the MTA data in Fig. 143.4 below. This again was determined by averaging each month the anomalies from the 65 longest stations and also suggests that the climate was warming slowly before 1980 but then warmed more strongly by over 1°C thereafter.
Fig. 143.4: Temperature trends for England based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1826-1975 and has a positive gradient of +0.27 ± 0.03°C/century.
The difference between the MTA based on raw unadjusted data (from Fig. 143.2) and the MTA based on BE adjusted data (from Fig. 143.4) is shown in Fig. 143.5 below. The blue curve in Fig. 143.5 is the difference in MTA values between the adjusted data (Fig. 143.4) and the unadjusted data (Fig. 143.2) and represents the total of all the data adjustments made including those from homogenization, gridding, Kriging and most significantly breakpoint adjustments. The orange curve is the contribution to those adjustments arising solely from breakpoint adjustments.
Fig. 143.5: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 143.4 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 small positive gradient of +0.003 ± 0.003 °C per century. The orange curve shows the contribution just from breakpoint adjustments.
The overall impact of any adjustments can perhaps be seen more clearly if we compare the 5-year averages for the raw unadjusted data and the BE adjusted data as is shown in Fig. 143.6 below. This shows that the two datasets agree almost perfectly from 1870 onwards while before 1870 the adjusted data implies the climate is more stable. It should be noted though that the MTA trends before 1870 are based on data from less than five stations and this drops to less than two before 1850 (see Fig. 143.3). This is one reason why the MTA exhibits more natural variability over the earlier period before 1870.
Fig. 143.6: The 5-year mean temperature change for England since 1760 based on the original raw data from Fig. 143.2 (in blue) and the Berkeley Earth adjusted data from Fig. 143.4 (in red).
Summary
What the raw data for England shows is that the climate was warming slowly for most of the period up to 1975 (see Fig. 143.2). This is similar to the trend seen previously for Great Britain (see Fig. 141.2 in Post 141), but is different from both Scotland (see Fig. 142.2 in Post 142) and Ireland (see Fig. 140.2 in Post 140) where little warming was seen in this period. This suggests that England is the dominant country in determining the overall climate of the UK but is also the outlier. But why?
The obvious answer is that England has a much greater population density and so experiences much more urban or surface heating from human activities (see Post 14, Post 29, Post 127 and Post 134). As I pointed out in Section (iv) of Post 127, the energy consumption of Greater London is sufficient to raise the local temperature by over 4°C.
Acronyms
BE = Berkeley Earth.
MRT = monthly reference temperature (see Post 47).
MTA = mean temperature anomaly.
Long station = a station with over 1200 months (100 years) of data before 2014.
Medium station = a station with over 480 months (40 years) of data before 2014.
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