I nearly spluttered out my crunchy nuts in bed this morning when I read this BBC news item about how researchers predict that summers in Scotland are going to progressively hotter and drier in the coming years, all no doubt all due to AGW or possibly the jet stream, you know that fast moving ribbon of winds high up in the atmosphere, one or the other. I decided to take a look a closer look at the temperatures of the “record-breaking” and “unusually hot summer” of 2018 thats mentioned quite frequently in the report.
The facts about temperatures in summer 2018
Well to be honest looking at the meteorological summer as a whole the mean maximum temperature anomalies don’t look that spectacular, and generally range between one and two degrees above the 1961-1990 LTA. I reckon that most locals will remember summer 2108 because it was sunnier than normal, particularly towards the end of June, when many of the extreme maximum temperature for 2018 were achieved.
You would expect that hand in hand with the words, hotter and drier, must come the word sunnier, and as far as sunshine was concerned in Scotland 2018 was 20% above the LTA, but despite this the linear trend since 1929 is almost flat lined. It’s only a shame that what this report found for summers isn’t as equally true for the winters in Scotland, as parts of the Highlands had little more than five hours of sunshine for the whole of January this year.
As far as rainfall is concerned summer 2018 was round 10% drier than the LTA. But again the linear trend since 1910 is flat lined – summers are not getting any drier in Scotland I’m afraid, and don’t forget, summer 2019 was the wettest since at least 1910 in Scotland.
The mean temperature anomaly for Scotland for summer 2018 from the 1910 gridded data of +1°C made it the sixth warmest since 1910. Despite this fact, the linear trends in maximum and minimum temperatures show only a modest rise in temperatures since 1910 in Scotland. I will admit that would have been a lot steeper rise if the linear trend had been restricted to the last 30 years.
Despite all the hype behind this report I remain very skeptical that summers north of the border will indeed be hotter or drier in the future. The only way they will is if anticyclonic east or southeasterly weather types become more common across the UK, and the frequency of Atlantic west or southwesterly declines dramatically. Of course I may be totally wrong in my skepticism about the researchers predictions and if so bring it on!