Occasionally, at this time of the year, I remember 1952 and the Great smog that settled over London that December.   The centre of a large anticyclone settled above the town trapping a layer of colder air close to the ground, held in position by an inverse temperature gradient
keeping a warmer layer above.  A fog developed, as one might expect under those conditions, but it was particularly dense.  People in something approaching a million homes tried to keep warm by lighting their coal fires but, because of the atmospheric conditions, the smoke   from their chimneys only reached little height before turning over and
sinking down to add to the fog, much of the industry was also powered by  coal fired steam boilers, town gas was produced from coal, and in the  middle of it all was the coal fired Battersea Power Station.  The smoke   from this coal burning contained a high proportion of particulates of soot and minute droplets of tar that added to the fog and increased its
density (Battersea did have filters to reduce their emissions of  particulates).  Road traffic also produced particulates including lead,  (although the lead tended to fall to the ground relatively quickly)  along with more pollutants.  Apart from the particles the exhausts from
all this combustion of coal and other fuels contained a number of  noxious gases, in particular the highly toxic and corrosive sulphur  dioxide as well as some oxides of nitrogen and small amounts of carbon  monoxide, together with a whole lot of carbon dioxide.  The net result was a ghastly yellowish unhealthy smog that tended to thicken over the
next few days.

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It’s getting even colder! Frost, rainfall and winds are increasingly common, sunshine hours are much reduced and it can be bitter with a risk of snow. You may not want to be working outside at this time of year, but luckily there’s not a lot to do!

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