Tonight, people in Great Britain will celebrate Guy Fawkes Day with bonfires and elaborate fireworks displays across the country, which is why it’s also known as Bonfire Night. The downside of the festivities is that the combination temporarily pours a lot of extra particulates into the air. This is known to have an adverse effect on visibility, but scientists also suspected that elevated levels of soot that accumulates from the annual bonfires could contribute to creating ice in clouds. According to a new paper published in the Journal of Geophysical Research: Atmosphere, this doesn’t seem to be the case.
For those not familiar with this British celebration, Guy Fawkes was a member of the infamous Gunpowder Plot of 1605, whose Catholic members conspired to blow up the British House of Lords in an attempt to assassinate the Protestant King James I. Fawkes was caught guarding the cache of explosives, and the public celebrated the king’s survival by lighting bonfires. Fawkes and his fellow conspirators were executed the following January. Just days before the executions, Parliament passed the Observance of 5th November Act (aka the “Thanksgiving Act”), making the day an annual celebration.
Originally marked by extreme anti-Catholic sentiment, the nature of the celebrations evolved over the centuries. It eventually became common practice to burn Guy Fawkes in effigy—a practice memorably depicted in the climax of a season 3 episode of the BBC’s Sherlock Holmes series (“The Empty Hearse”), in which Holmes and Watson foil a modern-day plot to finish what the Gunpowder Plot had started.
Science weighs in
This is not the first study to investigate the potential adverse impacts of Bonfire Night. A 2015 study by scientists at the University of Birmingham, led by Francis Pope, examined how all that extra smoke and debris in the air impacts visibility. They chose Nottingham for their study because it had nearby monitoring stations: one to monitor visibility and the other to monitor air pollutants. They used datasets tracking weather and air pollution over a 13-year period (2000-2012) and looked for any marked decreases in visibility coinciding with Bonfire Night.
The results: on average, there was a 25-percent reduction in visibility associated with Guy Fawkes Night. And in urban locations like Nottingham, where the denser population translates into more bonfires per capita, they found as much as a 60-percent reduction in visibility.
It’s quite natural for ice to form in clouds, but a high concentration of pollutants—dust, fungus, or bacteria, for instance—can give rise to supercooled water droplets that cause clouds to freeze. That, in turn, could have significant implications for the climate, according to Benjamin Murray of the University of Leeds, a co-author of the new study, possibly providing a buffer of sorts against rising CO2 levels—or, alternatively, amplifying those effects.
“Clouds which contain a mixture of ice and supercooled water probably buffer the effects of CO2, but the amount of buffering is highly uncertain and in part depends on cloud processes like ice formation on aerosol particles,” Murray told Ars. “It is the response of clouds to warming that is one of the major uncertainties to our projections of how much the planet will warm for a given amount of CO2 emitted by humans. Hence, we need to understand cloud processes, like ice formation on aerosol particles, in order to improve our predictions.”
The Guy Fawkes bonfires are typically set with fuels like waste wood—often containing preservatives and paints, depending on where it was salvaged—garden waste (branches, leaves, plant stems, etc.), and old newspapers and cardboard, as well as the occasional plastic or rubber items. The resulting “combustion aerosol” can even be seen from space. Murray and his colleagues hypothesized that, given those higher levels of aerosols, they should be able to detect more ice-nucleating particle concentrations in the atmosphere during Bonfire Night.
The particles produced on Bonfire Night are probably not important for making ice in clouds.”
“Ice nucleating particles have a dramatic impact on the properties of cold clouds, but our knowledge of which aerosol particle types make effective ice nucleating particles is in its infancy,” said Murray. “Before doing these experiments, we simply did not know if the types of aerosol particles produced on Bonfire Night (soot being an important type) nucleated ice under conditions relevant for an important class of cloud containing supercooled liquid water.”
But after pulling all-nighters in November 2016 and November 2017—sampling aerosol concentrations from the balcony of the Leeds University School of Earth and Environmental building—that’s not what they found. “Despite seeing massive increases in soot and other aerosol particle concentrations, we did not observe a change in the ice nucleating particle concentrations,” said Murray. “This showed us that the particles produced on bonfire night are probably not important for making ice in clouds.”
Pope et al. suggested that brief annual exposure to the bonfires shouldn’t result in too many seriously adverse health effects in human beings. (It can, however, be risky for late-night drivers heading home after a long night of celebrating, given the reduced visibility—especially in highly humid conditions.) By contrast, Murray and his colleagues emphasized that even though it doesn’t contribute to ice nucleation, Bonfire Night remains a major pollution event. “The soot will impact climate in different ways and also has negative implications for human health,” said Murray. That’s unlikely to keep the people of Great Britain from celebrating a centuries-old tradition, however.
DOI: Journal of Geophysical Research: Atmosphere, 2020. 10.1029/2020JD032938 (About DOIs).