London’s Great Smog of 1952

Big Ben mostly obscured by smog
December 5, 1952, was a chilly one in London, prompting residents to warm their homes by lighting their coal fireplaces and unknowingly contributing to a catastrophe that would kill thousands. The event only lasted five days, but it delivered a death toll of more than four thousand. Some researchers have estimated the number to be as high as twelve thousand.

What the unsuspecting Londoners didn’t know was that the cold that day was caused by an anticyclone poised over the city pushing air downwards and causing a temperature inversion, which is an upper layer of warm air trapping cold air at the ground level. Unfortunately, the smoke from the chimneys as well as emissions from factories and automobiles were also trapped. With no wind to disperse the smoke, what began as an ordinary fog quickly became a thirty-mile-wide mass of smog, nicknamed “pea-souper” due to its yellowish-brown color. Nightfall on December 5 only served to increase the smog and the morning sun was unable to burn it away. The same thing happened on the next two nights, causing the situation to grow even more dangerous.