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Has Increased Sunshine Caused UK Warming In Late 20thC?

December 21, 2014
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By Paul Homewood





The sharp rise in UK temperatures, which effectively began in the 1980’s, is widely known about, but, (and I may be wrong here), has never been satisfactorily explained. Indeed, I am not sure anybody from the Met Office, Hadley Centre, etc has ever seriously attempted to explain it.

Usually, whenever it is mentioned, it is brushed aside as “climate change”. I have always thought this to be nonsense, as, whatever our views of global warming theory, CO2 does not possess the magical properties that enable it to suddenly raise temperatures in such a way, thereafter followed by a decade long pause. Theory tells us that, as CO2 increases in the atmosphere, temperatures should rise gradually and steadily.


A few weeks ago, whilst checking something else, I became aware that around the same time that UK temperatures began to rise, sunshine hours also increased sharply, as the Met Office below shows. Indeed, not only did it rise, but it increased to levels well above anything seen since records start in 1929.




I naturally wondered whether there was a connection here, but was initially thrown as the largest increase in sunshine hours was during winter and spring, with little change in summer. This seemed counterintuitive, since we would normally associate bright, sunny winters with cold weather. At that stage, I filed it all away in my memory and went off to beat the wife instead.



However, in last week’s Sunday Telegraph, I came across this piece on December climate from Philip Eden, (as always, not available on line).




Now the jigsaw began to fit into place. The increase in sunshine hours, particularly during winter, was not caused by changing weather patterns but a reduction in air pollution. It is not unreasonable, then, to surmise that this increase in sunshine was, at least in part, responsible for the increase in temperatures we have seen.

As the graph below shows, there is pretty good correlation between sunshine and temperature.




There is nothing very new in this argument, as air pollution has often been quoted as the reason for the decline in northern hemisphere temperatures during the 1960’s and 70’s. However, that logic misses the point that pollution has been a major factor since the mid 19thC. If it is true that a polluted atmosphere can depress temperatures, then these temperatures have been lower as a result for a century or more.

With a cleaner atmosphere now, temperatures have simply returned to the level they would have been at in the past.


This phenomenon of a sharp rise in late 20thC temperatures is not limited to Britain. We see the same effect across much of NW Europe, for instance France and Germany, as GISS show:






Combined with the recovery of the Atlantic Multidecadal Oscillation, from its low point in the late 1970’s, how much has reduced air pollution, and therefore more sunshine, contributed to UK and European warming in the late 20thC?

  1. Kon Dealer permalink
    December 21, 2014 2:49 pm

    Great work, as always, Paul.
    Send it to the Met Orifice- see what they have to say.

  2. Bloke down the pub permalink
    December 21, 2014 2:54 pm

    My solar panels have produced more this year than the two preceding.

    • saveenergy permalink
      December 22, 2014 1:53 pm

      My readings in 12mth blocks are –

  3. December 21, 2014 3:01 pm


    Cloud cover affects the sunshine hours. Pollution simply reduces the intensity of insolation.

    The old urban-only ‘pea-soupers’ virtually ceased with the implementation of the Clean Air Act.

    • December 21, 2014 3:57 pm

      I don’t know how they measure whether it is sunny or not, but there must be times when there is enough haze to blot the sun out. Presumably the more air pollution there is, the more haze there will be.

      What really strikes me though is that the Met Office seem to have paid so little attention as to why there is more sunshine, for whatever reason. Clearly it can only undermine their agenda.

      • David Eyles permalink
        December 22, 2014 9:19 am

        The traditional device for measuring sunlight hours is a sphere of glass which is set above a curve of heat sensitive paper placed underneath. The glass ball acts as a lens which focusses the light onto the paper and leaves a trail. When the sun goes behind a cloud, no mark is made on the paper. When the sun emerges again, the trail starts again, leaving a gap because the sun has moved. Total hours of sunlight are found by measuring the length of the marks and adding together for that day. It means a new piece of paper for each day and I don’t know how waterproof they are. It also means having to collect and renew the paper each day.

        I have no doubt that they now have an electronic device which collects and stores the same data, but there aren’t many of the old fashioned manual types, because of the maintenance. The only one I have ever seen was at Plumpton Agricultural College in Sussex in the 90s. It was set in a grassed compound near, but not in the shadow of, the Stevenson Screen and the rain gauge. In those days it was well maintained and the data was properly collected.

  4. Ben Vorlich permalink
    December 21, 2014 3:55 pm

    Joe Public
    My first thoughts
    1. Clean Air Act
    2. North Sea gas

    Both leading to clearer air particularly in winter and spring initially from the 1960s but especially from the 1980s.

    • Joe Public permalink
      December 21, 2014 5:20 pm

      It was Towns Gas, manufactured from coal until the end of the 60’s.

  5. Chaeremon permalink
    December 21, 2014 4:46 pm

    Thank you for raising the awareness of sunshine, on solstice day 🙂

    Though it may appear farfetched, a small change in the area of the solargraph (say: near 1%), and/or its geometric form, can also contribute to sensible change, like cloudiness and pollution. I’ve compiled a query which demonstrates the non-linear area and form of the solargraph (hope that the search works for you):

    I’d be interested in before / after images over longer time-frames …

  6. David Eyles permalink
    December 21, 2014 9:21 pm

    Why not do a correlation exercise – sunshine hours against temperature. Two graphs that appear to follow each other is basically a crude correlation, but actually plotting it and doing the maths might be a lot more convincing.

    • December 21, 2014 11:35 pm

      Even a perfect correlation does not prove causation.

      But I believe that this data poses serious questions about supposed links between warming and CO2 that require answering.

      • David Eyles permalink
        December 22, 2014 9:00 am

        Quite so. But in doing that you are well on your way to showing that they are related. Cause and effect comes later with regression and other things.

        But, in thinking about this as I drifted off to sleep last night, I think you are on to something that no-one else has properly explored. I recall several of those temperature anomaly graphs which show a downward spike related to volcano eruption – The 1991 Pinatubo eruption springs to mind – causing millions of tonnes of ash to enter the atmosphere. So if volcanic ash is an acceptable influence on climate (scientifically speaking), why not steady industrial pollution, particularly as it was so pervasive from the industrial revolution right up until our industrial base changed from heavy industry to services in 1990s onwards?

        There should be air quality records available from Defra somewhere. They won’t be as long a time series as the daylight hours series, because I don’t think they were regularly collected until the ’90s, and then it was collected by local government, so I don’t know where they will be collated and stored, but Defra is the best bet initially. When John Gummer was Environment Secretary, Defra produced a regular report of environmental conditions in the UK. I am pretty sure they did air quality, but I can no longer find it (I had a hard copy once).

        A short series of air quality against sunshine hours might possibly add credence to the possibility that air pollution extended the cooling at the end of the cold period in the late 19th Century, well into the latter part of the 20th Century.

        Given that most of the temperature records, worldwide, are from stations which are in urban/semi-urban sites, we would expect industrial change to less polluting industries to increase warming quite quickly. We would expect the opposite to happen in China, which has industrialised very, very fast and over the same period.

        So keep up the good work. I think you are doing a superb job of providing those of us who read your blog with a wonderful reality check. It’s pity Julia Slingo doesn’t read it as well. She might stop making such an idiot of herself in making alarmist pronouncements if she did.

        Have a good Christmas,


      • December 22, 2014 10:56 pm

        Perfect correlation certainly does prove causation–it just doesn’t tell you (necessarily) what caused what, including unidentified causes. –AGF

  7. saveenergy permalink
    December 22, 2014 1:56 pm

    Is it coincidence that there’s 60yrs between peaks on smoothed curve ???

    Is there sun data older than 1929 ??

    • December 22, 2014 3:26 pm

      Philip Eden says there is data back to the 19thC , but the Met Office only publish from 1929.

  8. December 22, 2014 3:33 pm


    Since England has gotten a bit warmer, has the warmer temperature been, in itself, any kind of “problem”?

    • Billy Liar permalink
      December 22, 2014 5:10 pm

      Oh, yes. We’ve had to turn the fire hydrants on in the summer for relief from the baking heat.


    • December 22, 2014 5:40 pm

      Record harvests this year, and record low excess winter deaths.

  9. December 22, 2014 6:48 pm

    Another factor which influences temperature in the UK is wind direction.
    Unfortunately there doesn’t seem to be much (any?) historic data on this from the Met. Office.
    A quick check on November’s CET (using wind direction from Pershore observations) showed that the average temp, when the wind was coming from the N-ENE direction was 6.6c, while from S-WSW it was 10.9c.

    I suspect that this year’s high mean CET is at least partially due to wind direction.

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