London Fog Scientific Fact or Myth

The image of London, England is of a city often wrapped in a dense fog of moisture that permeates everyone and everything, but you may wonder if this is an accurate picture of this European center of business and tourism. Many scientific factors contribute to the conditions that make “a foggy day in London town” a reality.

London’s Location

The country of England is located on a small island surrounded by water, which gives it a temperate maritime climate. This creates variable weather that can change frequently from area to area. Rainfall is evenly distributed throughout the year, making the climate generally damp. Temperatures rarely fall below freezing and are usually moderately warm throughout the summer. London’s reputation for being a foggy city comes from older times when this crowded city heated its homes and businesses with coal. The soot and debris that resulted combined with the moisture in the air to create a thick soup of foggy air. The city of London sits in a low elevation with the Thames River nearby, so that caused fog to hang over the city a good deal of the time. Today, however, the fog, or smog, is much less common, though you can still experience the London fog at certain times of the year when large amounts of moisture are present in the air.

What Causes Fog?

Fog is essentially a cloud sitting at ground level. This cloud forms when the warmth of the ground meets cold air drifting into the area. The air cools and loses the ability to hold water as a gas. The water is released as water droplets that are visible to the eye. These droplets easily form around tiny specks of dust, dirt and sea salt. The light that hits these droplets splits into many visible wavelengths, creating a whitish color that we recognize as “the London fog.”

Fog or Smog?

Fog is composed of water droplets. Smog is a combination of the words “fog” and “smoke,” to make “smog.” The smoke comes from the burning of fossil fuels that release large amounts of smoke and soot particles. It is much thicker than normal fog and can have an impact on breathing. Because it was a center for business and industry, the city of London was subject to heavy smog problems. In recent years, the city tackled industrial pollution so that its smog problem has decreased considerably.

London’s Famous 1952 Fog

In December of 1952, the city of London suffered a catastrophic fog that seriously impacted the lives of its residents. The weather had been unusually cold in the weeks preceding the fog, and people had been burning more coal to keep warm. This action cause an increase in smoke and sulfur emissions in the air that made the fog’s water droplets easy to adhere to the particles. The thick, smoke-polluted air hung over the city, and visibility was reduced to a few feet. Road, rail and air transportation was brought to a standstill as the city waited for the fog/smog combination to lift. This “killer fog” caused thousands of deaths from bronchitis, pneumonia, tuberculosis and heart failure due to breathing problems. Many people experienced impaired respiration, asthma and lung damage. It is believed that up to 12,000 people were killed by the heavy, dirt-laden fog. This catastrophe caused the city of London to enact new pollution standards to prevent a recurrence of the problem.

Though less vulnerable to foggy conditions that it once was, London still experiences many periods of fog during the year. Visitors to the city are less likely to notice it, depending on when they come to the city.