Cleaner Air, Sunshine & Temperatures – Watts Up With That?

From NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

Spring this year was by far the sunniest on record in the UK. Given that last year was one of the least sunniest, we need to accept that natural variability plays the major role in all of this,

But question marks remain about the longer term trends, which are clearly increasing.

Which brings us to the question of aerosols and air pollution.

There is absolutely no question that aerosols reduce the amount of sunlight reaching the surface or that they act as cloud condensation nuclei. This is what the Met Office say:

However, human activities are also responsible for increasing the atmospheric concentrations of microscopic particles, such as sulphate from industrial sulphur dioxide emissions; smoke from burning of agricultural waste, and pollution particles from traffic emissions.

These atmospheric particles scatter and absorb sunlight and terrestrial radiation and also act as cloud condensation nuclei and modify the microphysical and optical properties of clouds.

The net effect of the impacts on radiation and cloud properties is to induce a net cooling of the climate system which acts to oppose the warming due to increases in greenhouse gases.

https://www.metoffice.gov.uk/research/climate/earth-system-science/aerosols

And NASA established that reduced air pollution during the pandemic caused measurable warming in some areas:

The COVID-19 pandemic showed what can happen if the humans reduce their aerosol pollution. Fossil-fueled air travel, driving, electricity use, and industrial activity all decreased sharply in the spring of 2020. This led to cleaner, clearer air, which caused a slight warming — up to 0.2 to 0.5° F (0.1 to 0.3° C) — in some places.

Aerosols: Small Particles with Big Climate Effects

So how much of that extra sunlight we have been experiencing in the UK since the 1970s is the result of cleaner air?

The Met Office produced the graph below, which shows just how remarkable the decline in pollution has been.

https://www.metoffice.gov.uk/blog/2024/how-is-uk-air-quality-landscape-changing

While cities like Birmingham were obviously badly affected by dirty air in the past, this pollution was inevitably spread more widely across the country by winds. And in the last few years we have had reduced sulphur emissions from shipping to add to the mix.

And the Met Office’s State of the UK Climate Report last year admitted that cleaner air was a factor in increased sunshine:

https://www.metoffice.gov.uk/research/climate/maps-and-data/about/state-of-climate

A 2006 study by the Met Office found a strong correlation between sunshine and temperatures in spring, summer and autumn:

https://web.archive.org/web/20240317075352/https://web.archive.org/web/20151001000000*/https://www.metoffice.gov.uk/media/pdf/q/h/uk_climate_trends.pdf

Which all begs the question – what impact has cleaner air had on the rise in UK temperatures since the 1960s?

And why is the Met Office so reticent to mention it?

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