Local (not Global) Warming - comparing local temperature datasets

 Previously, in January 2021, I looked at how annual temperatures have changed in Herefordshire over the 1931-2020 time period using UK Met Office data from their weather station in Ross-on-Wye. I can now add a further two years to this dataset and replot the mean annual temperatures ...

Annual Temperatures (℃) for Ross-on-Wye (1931 - 2022)

[NB: Annual mean temperatures calculated by averaging monthly maximum and minimum temperatures (Tmax+Tmin/2). This is not optimum but is the best I can do with the data provided by the Met Office. I have made no allowance for the different number of days in the months of the year when estimating annual mean temperature but is not a minor error. If I ever have enough spare time to do a 'proper' job then I will be truly amazed but I am prepared to give it a go if I have the data!!]

The Central England Temperature (CET) data set, maintained by the UK Met Office Hadley Centre, is the longest instrumental temperature record in the world; daily and monthly temperature values have been recorded from 1772 and 1659 respectively. The CET data covers an approximately triangular area from Bristol to London to Manchester ...

Area covered by the Central England Temperature (CET) data set

Both Hereford and Ross-on-Wye lie just outside the CET area but they are near enough for the CET data to be a good proxy for Herefordshire temperatures and local warming trends. This can be seen very clearly by comparing the annual mean temperatures for Ross-on-Wye (top of the page) with the equivalent CET results (below) for the 1931 - 2022 period.

Annual CET Data (1931-2022)

My Davis Weather Station has been running for just over three years collecting weather data every 15 minutes. So how do the temperatures recorded by my weather station compare with similar data collected from the nearby Ross-on-Wye Met Office station and the more geographically extensive CET network?

Let's have a look! The following three bargraphs compare all three of the above datasets on a monthly basis (an annual mean is included for completeness) for the years 2020, 2021, and 2022.

Mean Monthly Temperatures (2020) from Davis Weather Station, Ross-on-Wye Met Office Weather Station and CET

Mean Monthly Temperatures (2021) from Davis Weather Station, Ross-on-Wye Met Office Weather Station and CET

Mean Monthly Temperatures (2022) from Davis Weather Station, Ross-on-Wye Met Office Weather Station and CET

From which we may conclude:

• Excellent agreement between all three datasets
• The Davis and the Ross-on-Wye Met Office Weather Stations show the closest agreement in temperature values.
• There is a small bias towards higher temperatures for the Davis Weather Station - possibly an Urban Heat Island (UHI) effect
• The CET values show good correlation with the other two datasets but with a clear bias to lower temperatures. Probably explained by the fact that the CET geographical area includes more northerly weather stations (see map above)

The longer (1931-2022) temperature datasets show a very clear warming trend in Herefordshire and Central England commensurate with the well-established trend in global warming noted in numerous IPCC reports.

Equally obvious is that the seasons here in Herefordshire are changing and becoming more variable which is not good news for gardeners and farmers alike. The weather data from my Davis Station only covers the last three years. Nevertheless, I hope to take a deeper dive into all the weather data to see if any trends are discernible and what this means for the future.