Fascinating. After about 1972 the cumulative effects of the UK’s Clean Air Acts and central-heating installations probably had a nice side-effect… they gave the Midlands significantly more sunlight in winter and on sunny autumn days. The sun became able to cut through what had before been man-made fug and smoke and haze…

Since 1929… “significant changes [in total sunlight hours] occurred in the winter season, when there has been an increase in sunshine of about 20% for central and northern England. Sunshine has also increased in these areas by about 10% in autumn.”

“These increases could be a result of the Clean Air Acts of 1956 onwards, which has led to a decrease in air pollution.”

The effect was especially marked after about 1970. So… 20% more sunlight reaching the ground in winter by 2004, largely because the winter coal-fires were no longer burning in millions of homes. And it may well have ticked up by a further 5% in 2005-2020, though that’s my guess rather than the Met Office’s figures.

The upward inflection point in sunniness starts around 1972 for the Midlands, according to an accompanying graph. That’s about right, 1970-72 being the point when many middle-class people had central-heating installed and turned the old coal-shed into an outside loo for the garden. The trend would have been amplified by the Oil Crisis which affected industry and began in 1974, alongside wave after wave of nationwide industrial strikes from 1974-79 (factories standing idle etc). Then there was another burst of central-heating installation when Mrs Thatcher gave people the right-to-buy their rented homes in the mid 1980s. The Thatcher revolution of the 1980s also meant that many of the inefficient old ‘smoke stack’ industries were swept away by circa 1986.

Average surface temperatures also then nudged up slightly, in tandem with the increased sunlight. It got a bit warmer because smog, mist and haze was artificially cooling the land, by blocking warming sunlight. I imagine that the effects were especially pronounced in somewhere like Stoke-on-Trent. The city being said to have been smoky, especially at times when the pot-banks were firing their wares. It might then be an interesting historical exercise to see if the change can be tracked on the ground, in the data at the city-region level in the Potteries, and if the sunniness effect was actually greater in Stoke-on-Trent. That assumes, however, that the data still exists somewhere in its original un-tampered state. There will also be natural variation to accommodate, for instance the city’s 1986 Garden Festival had a terrible summer of near constant rain, wind and cloud. Not much sun was seen during that entire spring/summer, by all accounts.

Source: National Climate Information Centre Climate Memorandum No. 21, 2006, UK Met Office. Using a data-set that ran to 2004.