The impact of the heavy bombing runs by Allied forces over Germany during World War II are pretty stark; post-war images show entire swaths of cities, including Hanover, Hamburg, Dresden and Berlin reduced to rubble. Between 1940 and 1945 the U.S. and Great Britain dropped 2.7 million tons of explosives in Europe, half of that on Germany alone, killing 410,000 civilians.
But the impact of the bombs wasn’t just felt on the ground. Ashley Strickland at CNN reports that a new study shows the shockwaves produced by the aerial ordnance were so intense they reached the edge of space, impacting Earth’s upper atmosphere.
For the study, researchers looked at the archived daily records of the Radio Research Station at Ditton Park close to Slough, England, a facility that kept track of the ionosphere every day from 1933 to 1996, the longest continuous set of ionospheric measurements ever taken. The team is trying to understand if and how events on earth— like volcanic explosions, earthquakes or lightning—can affect the upper atmosphere. So they decided to look for a predictable stand-in for those cataclysmic events and analyzed the 152 largest Allied air raids over Germany.
According to a press release, the team found that the shockwaves from the bombs reached the ionosphere, causing a significant reduction in the concentration of electrically charged particles in the atmospheric layer. The effects could last up to 24 hours and stretched out all the way over England, which was 600 miles away from the blast zones. The research appears in the journal Annales Geophysicae.
“The images of neighborhoods across Europe reduced to rubble due to wartime air raids are a lasting reminder of the destruction that can be caused by man-made explosions,” lead author Chris Scott, a meteorologist at Reading University in the United Kingdom, says in the release.
“But the impact of these bombs way up in the Earth’s atmosphere has never been realized until now,” he continues. “It is astonishing to see how the ripples caused by man-made explosions can affect the edge of space. Each raid released the energy of at least 300 lightning strikes. The sheer power involved has allowed us to quantify how events on the Earth's surface can also affect the ionosphere.”
Strickland reports that the team decided to look at the Allied bombing raids for several reasons. First, German bombing raids during the London Blitz of 1940 and 1941 were closer to the Ditton Park research site, but those raids were more or less continuous, making it difficult for researchers to tease out the impact of the bombing from seasonal changes caused by the sun. The German bombers were also smaller than later Allied planes, carrying about 4,400 pounds of bombs versus the 12,000 to 22,000 bombs that could be dropped by American and British forces. Those big booms, which took place only occasionally, were easier to find in the data and much better suited for the study.
It’s not clear if these ionosphere disruptions had much impact during World War II. The ionosphere, a region of charged particles and plasma that stretches 30 to 620 miles above the Earth, is able to bounce radio signals, which made it important for long-distance radio communication during the war. In the modern era, the ionosphere is important for radio, GPS, radar and radio telescopes, meaning disruptions—natural or man-made—are a much bigger deal than they were in the 1940s.
The researchers believe that the shockwaves would have heated the upper atmosphere, causing the loss of electrons in the ionosphere. Now, the bomb data may allow the researchers to begin to understand just how much energy it takes to impact this important atmospheric layer.
“Because we know the energies involved in these explosions, that gives us a real quantifiable way of assessing how much energy is required to make the ionosphere warmer,” Scott tells CNN’s Strickland. That data could then be used to estimate the impact of shockwaves generated by volcanoes, lighting and earthquakes.
The team hopes to refine their calculations even further and would like to start digitizing early atmospheric data with help from the public so they can figure out the impact of hundreds of other smaller bombing raids that took place during the war.