Why have sunny winters in the UK become more frequent since 2000?
It’s a good question, but I’ll admit now that I don’t know the reason why winters since 2000 have invariably been sunny affairs in the UK. I only recently noticed that this was the case after updating some code in an application I had written to visualise the gridded monthly data from the Met Office.
Here is a table of the sunniest winters [DJF] since 1929 and you can now see what I mean about how sunny some of the last 20 winters have been across the UK.
Winters getting sunnier
As you can see from the bar chart winter sunshine has been increasing at the rate of 2.6 hours per decade across the UK since the record started in 1929. Rather strangely I would have expected to see an increase in sunshine in the years immediately following the introduction of the Clean Air act in 1956, but the 10 year moving average looks fairly flat from 1948 to 1963, and then it declined until the mid 1970’s. Perhaps I’ve screwed up somewhere, because the sunshine figures for the Midlands show a very similar story after 1956. Perhaps the results of the act took 15 or years or more before they kicked in?
What happened to the records before 1929?
The gridded sunshine data record only begins in 1929, although there is no reason why it shouldn’t stretch back much further, even back to Victorian times (1853) when the Campbell-Stokes sunshine recorder was first invented. But you know how it is the Met Office have been busy doing other things, and they never got round to digitising all their handwritten climatological records which includes daily rainfall and sunshine values – give them a break – they’ve only had the data for 90 years or more. But help is at hand – they’ve recruited a whole load of volunteers to do there work for them – while they busy themselves with the climate crisis and how warm it’s going to get globally.
But sadly it appears that after helping out with the digitising of the Ben Nevis observational data, Weather Rescue aren’t involved with the digitising of daily climate records before 1929 (or 1910 come to that). So it maybe a long time before we see the Met Office extend there sunshine records back before then. As an example of that missing data, here are the sunshine totals from the Daily Weather Report for the 1st of March 1927. Only 35 out of 43 made a return on that day (but the present sunshine network is still pretty thin) although I’m sure there must be written records that have been squirreled away in the archives from climate stations who like today only make monthly returns.