The snow that brought London to a standstill earlier this week had one positive benefit: The air became less polluted.
As the British capital was blanketed by eight inches of snowfall – the biggest in decades – flights in and out of Heathrow ceased, traffic dissipated, and, for the first time ever, the city's famous double-decker buses stopped running.
And, as the Guardian pointed out Tuesday, Londoners could breathe a little easier.
Reporter Leo Hickman noted the air-quality readings taken on the corner of Marylebone Road and Baker Street, which normally sees 50,000 vehicles a day. The readings, measured by the London Air Quality Network at King's College London checked for concentrations of nitrogen oxide, which is thought to irritate the lungs and contribute to acid rain, and fine particles of 10 micrometers or less, which are also thought to cause health problems.
Here are the readings on that corner for a typical day, according to the Guardian:
Nitrogen Dioxide – 110 parts per billion
PM10 particulates – 85 micrograms per cubic meter
And here are the readings for February 2nd:
Nitrogen Dioxide – 15 parts per billion
PM10 particulates – 22 micrograms per cubic meter
As the London Air Quality Network's Timothy Baker explained to me over the phone, London was already enjoying particularly clean air because of "favorable meteorological conditions," that is, the air mass was coming in from the west, which is mostly ocean, instead of from the Continent, where it is laden with pollutants from the rest of Europe.
This sharp reduction in pollutants in such a short time demonstrates how air quality can be quickly improved once the source of pollution vanishes. Beijing learned this lesson last summer, when in anticipation of the Olympic Games it banned cars on alternate days, froze construction, shut down quarries and steel mills – and saw its everpresent photochemical haze replaced by blue skies.
Such measures do little to mitigate greenhouse-gas emissions in the short term, however. Last week, a major study found that even if humans were to stop burning fossil fuels, the effects of global warming will linger for at least a millennium.
As for London, on the same day that the city was breathing its unusually clean air, Mayor Boris Johnson announced that he would be suspending a plan to tighten emissions standards on trucks and buses, saying that the move would have a "detrimental impact" on small businesses.
Writes the Guardian's Mr. Hickman: