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Rise In UK Temperatures & Sunshine May Be Due To Reduced Air Pollution–Met Office 2006

September 24, 2018

By Paul Homewood



There is another piece of the jigsaw on the role of that big orange thing in the sky.

Back in 2006, the Met Office published the “Climate Memorandum No 21” Report. The original link I had no longer works, but it is still there on Wayback:



It looks at a full range of climate data, to identify trends and correlations since 1910, but I was particularly interested in the data on sunshine hours:




Most regions had seen significant increases in sunshine hours. The exceptions were N Scotland, N Ireland and SW England, all largely unaffected by air pollution. Note the report’s comment that this could be the result of Clean Air Acts of 1956 onwards.

But what effect could this have?

The Report sums up the relationship between all of the variables. (Remember that the correlation co-efficient goes from 0 to 1, with 1 being a perfect correlation, and even 0.7 being a “strong linear relationship” (see here). Zero, of course, tells us there is no relationship. Minus co-efficients work the same way, except the relationship is negative – eg more sum = less rain).



There is  a particularly strong correlation between sunshine and mean temperatures in both spring and autumn, though surprisingly less so in summer. In winter there is a weak negative relationship. As the Report states:

There is quite a strong positive correlation between maximum temperature and sunshine, especially in the spring and autumn, with values of r up to 0.85. Minimum temperature is negatively correlated with sunshine in the winter, and positively correlated in spring and autumn, but with lower values of r than for maximum temperature.


 It also includes these maps:.



The biggest increases are in winter, but of course these are percentages, so will translate into relatively smaller increases in hours.


So we have:

1) An increase in sunshine hours over the record.

2) The strong likelihood that this is at least partly due to reduced air pollution.

3) Strong correlation between that increase in sunshine, and the rise in mean temperatures over the period.



Furthermore, there has been little trend in winter temperatures. Most of the increase has come from the other three seasons:

 UK Mean temperature - Winter

UK Mean temperature - Spring

UK Mean temperature - Summer

UK Mean temperature - Autumn


All of the above flies in the face of the generally accepted theory that higher temperatures in the UK have been caused by GHGs.


There are two more parts to the jigsaw:

1) Mean sea level pressure data shows no significant trends since 1961, meaning that the increase in sunshine hours does not appear to be connected with it.



2) There has been a steady increase in vapour pressure, and as the correlation table showed, this is strongly related to rising temperatures during all four seasons.





Which brings us back to the rise in near-coastal SSTs, mentioned in my earlier post.

What caused SSTs to rise?

The obvious conclusion is that the increase in sunshine, for whatever reason, has warmed both the waters and land. Warmer seas then reinforce those land temperatures.


One question remains. The Met Office knew all of this in 2006, yet as far as I am aware the question of sunshine trends has largely been ignored by them since. Instead, with classic tunnel vision, they look no further than CO2 to explain the small rise in temperatures over the last few decades.

  1. September 25, 2018 1:02 am

    A long time ago, when I first became interested in “Global warming” I read a good article on pan evaporation rates which pointed to a change in sunshine being a significant cause of warming. Soon after it was changed by Connolley to remove that implication.

    And the cause, is very likely to be a reduction in air pollution as a result of 1970s clean air acts (the pollution used to cause sunshine blocking clouds aka smog)

  2. September 25, 2018 6:02 am

    Thank you for the hard work you put into this site – it is much appreciated.

    The more I get sucked into this global warming stuff the more confused I get.

    ‘Airborne pollution’ is surely just another word for aerosols and other airborne particulates. If their presence in the atmosphere reduces the amount of sunlight reaching the surface, this surely only means that the ‘missing’ energy is absorbed a little higher up, presumably causing warming in the lower troposphere and below.

    In other words, the presence or lack of air pollution doesn’t change the overall energy balance (if the albedo remains the same).

  3. david permalink
    September 25, 2018 6:57 am

    “…presumably causing warming in the lower troposphere and below.”

    Only part of it (energy from intercepted sunlight) will cause warming near the ground where most thermometers are. The rest will be soon be re-radiated from the atmosphere back to space, to be lost. As a matter of fact a large part of the sun’s energy is already absorbed by the atmosphere. If all of that suddenly penetrated to the surface, we would find ourselves very uncomfortable

    We are really talking about an “adjustment” to our measurements on the ground so that we do not draw false conclusions about the whole system. Of course a sane person simply welcomes a little more sunshine and warmth in the tiny part of the world that is England, and does not care tuppence about the why and the wherefore, and does not draw the conclusion the whole world is burning up.

  4. paul weldon permalink
    September 25, 2018 9:29 am

    You put together a good case, but may I make one point? You state that there is little trend in winter temperatures, but the graph you show for winter is deceptive. It covers 7 degrees C whereas the others (spring, summer and autumn) only cover 4 degrees C. If you stretch the graph vertically to compensate for this then the observed trend becomes more significant. Or look at the range of the ‘trend’: for winter, 1 degree. spring 1.1, summer 1.2 and autumn 1.5. My take would be that there is little difference except for the autumn, where the recent high averages stand out. That may be when there is more fog around which backs up your argument, it could also be that winter actually starts later than in the past, Certainly the cleaner air has made a difference to the number of sunshine hours recorded, and although that has made some difference to temperatures, it is only going to have a small effect, bearing in mind when the fog/smog is likely to occur. One has to look further afield for the cause of the warming at the end of the last century as it was more widespread than those areas influenced by air pollution. My guess would be that the Atlantic has been bringing both warmer water and air to NW Europe influencing both air temperatures and distribution of weather systems. Why? I have no idea! AMO? Maybe more effect than cause.

  5. tom0mason permalink
    September 25, 2018 9:51 am

    And as the clearer atmosphere was explained to the Great British public, the dawning of a bright new sunshine day warmly hit home, and the crowds went wild…

    And some old wags observed that sometimes it takes a long time for the penny to drop.

  6. Malcolm Bell permalink
    September 25, 2018 10:24 am

    Is it getting colder in China and India?

    • david permalink
      September 25, 2018 12:27 pm

      This site

      has what are described as monthly average temperatures for the whole of China from 1900 to 2015. I looked at the hottest month – July – and extracted the numbers; and then made an average of these for the decade 1901-1910, Ans. = 19.09 C. Similarly for the decade 1991-2000, Ans. = 19.70 C. Finally, for the period 2001 – 2015, Ans. = 20.05 C. It is interesting that the data for the last two years in the series, are actually lower than 20.05 C, being 19.87 C for 2014 and 19.81 C for 2015.

      So, presumed extra pollution in the present century does not seem to have obviously caused any cooling. But then China is quite big and most of it is NOT polluted anyway.

  7. saparonia permalink
    September 25, 2018 10:56 am

    They got rid of some sunshine here, this is yesterday near Sheffield – 24th September 2018

    • September 25, 2018 6:27 pm

      Notice the contrails. Jet travel brings pollutants and water vapor to the upper atmosphere.

      • Algicasi permalink
        September 26, 2018 9:34 am

        I presume you do not fly to your holiday destination then 🤣

  8. saparonia permalink
    September 25, 2018 10:58 am

    Tried to post this, was unable to see it, apologies if it appears twice.

    This was taken yesterday, 24th September 2018 South Yorkshire. They got rid of some of the sunshine.

  9. Mack permalink
    September 25, 2018 11:12 am

    Very interesting and perceptive analysis. Well done Paul.

  10. Tony Budd permalink
    September 25, 2018 11:41 am

    Those of us who remember London in the 1940s and 1950s would agree entirely. What counts as thick fog now would have been a light mist then. There were many occasions when the fog was so dense you could hardly see to walk let alone cycle. And of course the fog layer simply reflected most of the incoming sunshine back into space, leaving us cold and dark. A moderately rapid change came after the Clean Air Act in 1956 – the last dense fog I remember was in the 1963-4 winter, though by 1971 there were still some fairly heavy ones.

    • September 25, 2018 12:21 pm

      Pittsburgh, PA was very interesting in those times. I remember the ’50’s and early ’60’s when we would travel there for major shopping. It was the steel mills. The steel mills are returning, thanks to President Trump, but today there are methods to keep the pollution from entering the atmosphere.

      Almost all of our cities are built along rivers. Places such as Pittsburgh are on confluences of rivers. There the Monongahela River (which flows past Morgantown less than a mile from my home) and the Allegheny River meet to form the Ohio River.

      Rivers are in valleys which they created. These locations have temperature inversions, due to the topography, which keeps the “pollution” over the city.

  11. DaveR permalink
    September 25, 2018 11:45 am

    Met Office admits ‘frustration’ at ‘cherry-picked data’:

    “For Professor Peter Stott, who leads the climate monitoring and attribution team, 2018 is providing yet more solid proof of climate change. “The evidence is now cast iron solid that the world is warming and it is due to greenhouse gas emissions,” he says. “It is very frustrating when some people try to construct what might look to a naïve eye plausible sounding arguments but they are usually cherry picking data or constructing narratives that don’t accord with reality.”

    100% science-free and 100% propaganda. Make you feel quite proud, Peter?

    • david permalink
      September 25, 2018 12:08 pm

      Not only cast iron but solid as well…

      My English teacher would have thrown a chair about, and shouted, “Redundancy!”

    • Gerry, England permalink
      September 25, 2018 1:52 pm

      So he is basically saying ‘leave the cherry-picking and reality distortion to us’. Well, they are the experts at both.

    • September 25, 2018 2:55 pm

      There seems to be a concerted effort to declare victory in the climate “debate”, based on events in 2018. The BBC World Service was at it yesterday, wheeling out arch-alarmists such as Michael Mann.

      The problem is that most readers/listeners will swallow it completely, even though most of it is simply listing weather extremes, as if they never happened before. The young are obviously highly susceptible to this simple propaganda trick.

  12. Athelstan permalink
    September 25, 2018 1:03 pm

    But Paul, pollution is killing us all!

    See the government figures they never lie, never evah and a trillion, trillion times ovah see how they did that. 60K more mentally affected ‘pollution’ cases, 44k p/a deaths put down to particulates etc, illusion and statistics and conveniently forgetting some very salient facts. Liars can figure. One could almost surmise that, the EU-UK province had an agenda.
    [off sarc]

    In reference to the core of the blog post. I note that, cloud physics are incontestably related to the interaction of the solar influence and evaporation rates et bloody cetera.

    It is true that, on days in our UK winter, during blocking anti cyclonic conditions the addition of soot particulates and suphurous, nitrous aerosels ex millions of coal fires and industrial processes and vehicular transport made for, some very mucky UK air. Murky air indeed and across all of Europe.
    The clean air act helped Britain without and the beneficent help of the EU greatly diminish the great ‘pea soupers’ of the Fifties.

    Britain is blessed by, admittedly not totally exclusively, fundamentally affected by, an airstream and thanks to the Coriolis effect drifts south west to north east over the country.

    Although, I am convinced by the arguments of a longer growing season in this nation since circa the LIA an though I acknowledge your thoughts and no doubt it is part of the overall ‘climate picture’ I do not really believe that, ‘clean air’ IMHO is any significant climate factor, here in Britain. The sun is, clouds are, we like clean air fortunately the UK has a great A/C system, it just doesn’t work that well in when winds fall light usually in Anticyclones.


  13. September 25, 2018 3:11 pm

    The relative importance of clouds vs. aerosols in global dimming and brightening is debated by experts in the field. Martin Wild leads the research at ETH Zurich which hosts the global database of surface radiation measurements, both SW and LW. Some studies in the Mediterranean region conclude that clouds are the major factor. Wild provides this summary of observed tendencies in solar radiation:

    Further details at

  14. September 25, 2018 3:55 pm

    Unless air pollution blocks out the sun altogether, how could it affect sunshine *hours*? The report admits sunshine hours decreased in some areas after air pollution was reduced, casting more doubt on a direct link.

    • matthew dalby permalink
      September 25, 2018 5:40 pm

      Air pollution will create more clouds by providing nuclei that water vapour can condense on, therefore the pollution could be invisible to the naked eye but still help more clouds to form and block out the sun. I don’t see how there can be a simple correlation between less cloud and higher temperatures, as less cloud will lead to cooler nights. Also the mean temperatures for Britain show a similar pattern to global temperatures (rising at the start of the 20th century, decreasing slightly aprox. 1945-75, then increasing again) so either pollution was widespread enough to affect global temperatures or there was at least one other factor involved, either natural cycles (my opinion) or carbon dioxide.

      • September 25, 2018 6:02 pm

        The beryllium-10 records are interesting…
        An Antarctic view of Beryllium-10 and solar activity for the past millennium

        The lowest solar activity is found during the so-called Spörer Minimum (around AD 1450). The highest activities are found during the 8th century and over the last decades: as shown in previous studies, our results suggest that the recent solar activity is not exceptionally high for the last millennium.

    • September 25, 2018 10:08 pm

      What the report says is that sunshine has decreased in N Scotland, N Ireland, SW England and S Wales, all upwind of most air pollution.

      The greatest increases have occurred downwind of major conurbations

      Also don’t forget Table 15, which shows strong correlation between sunshine and temps (esp max) for all seasons except winter.

      (BTW – just a thought – but I was surprised at the weaker correlation of summer temps, compared with autumn and spring. Maybe the sun is so strong in summer that a bit of air pollution makes little difference. Whereas in spring and autumn, early morning haze can depress temperatures all day??)

      • Algicasi permalink
        September 26, 2018 9:41 am

        Thanks for all the brilliant and educational articles, Paul. As a pilot, I am used to operating into and out of persistent fog/freezing fog (descending from a clear blue sky with wall-to-wall sunshine into the murk at about 500 feet on the approach) in 3 of the seasons. If fog does appear in the summer under a clear sky, it burns off into low stratus very quickly and then the cloud dissipates equally quickly to leave a lovely sunny day.

  15. Bitter@twisted permalink
    September 25, 2018 6:19 pm

    there are so many factors that have been ignored by the AGW cultists.
    This is another.

  16. john cooknell permalink
    October 3, 2018 9:20 pm

    In the pre-amble of report Mathew Perry actually says that there was no trend in Temperature till the 1980’s.

    When a trend suddenly appears it can be genuine, an error, or confirmation bias. Of course the scientists would not have missed confirmation bias, apart from all of the times they have!

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