It reads like something out of a disaster movie. A large-scale volcanic eruption, like the 1991 eruption of the Philippines' Mount Pinatubo, could set off a chain reaction that would dramatically damage the Earth's ozone layer—thinning it out by as much as 25 percent, according to a recent study conducted by scientists from Harvard University and the University of Maryland.
The study sheds light on the consequences of something that's long posed a problem to the Earth's ozone layer: the effects of CFCs—the chemical that once made refrigerators and air conditioners so cold and aerosol hairspray so easy to spray. CFCs were phased out decades ago, but the chemical compounds continued to stick around in the atmosphere. Now, scientists believe that the presence of these CFCs could make volcanic eruptions far more dangerous for the environment than previously believed.
"If volcanic halogens, which are commonly present in large quantities in volcanic eruptions, were to partition substantially into the stratosphere — in any greenhouse gas emission scenario, at any point in the future — it would potentially cause severe losses of stratospheric ozone," said Eric Klobas, the study's lead author.
What does this mean, in plain speak? It means that it takes a lot longer than we thought for the Earth's environment to recover from damaging pollutants like CFCs. Large-scale volcanic eruptions are rare, but when they do happen the entire globe can feel the effects.
Tambora, still the world's largest volcanic eruption, changed the climate of the Earth for years after it blew a hole in North Sumatra. An estimated 70,000 people died from the initial eruption, but the lingering effects of having that much ash in the atmosphere killed hundreds of thousands more. Colder temperatures caused by the ash resulted in famines, revolutions, and civil unrest worldwide—making it one of the single most-important events of human history.
But we don't need to see another Tambora-sized eruption to see global change. Volcanos have a dual purpose on Earth. These eruptions can both thin the atmosphere by projecting depleting compounds into the sky, and also cause it to thicken. We're currently on the tail-end of a thinning period, but scientists thought that the Earth would transition back to a thickening phase sometime between 2015 and 2040. This recent study now shows that this transition is likely going to occur far later than predicted. We likely won't see a serious reversal until sometime around 2070, the study's authors found.
"Our model results show that the vulnerability of the ozone column to large volcanic eruptions will likely continue late into the 21st century, significantly later than previous estimates," said David Wilmouth, one of the study's authors.
What does a thinner ozone layer really mean? The ozone protects us all from the harmful effects of a type of the sun's radiation called ultraviolet B. This kind of radiation causes skin cancer, cataracts, and it messes with the growth of phytoplankton—the bottom rung of the ocean's food chain.
So how did scientists initial estimates fall so far short of these revised predictions? They reportedly forgot to take into account the halogen gases produced from natural sources like plankton and microalgae, Kolbas explained. These gases are now known to play an important role in whether volcanic eruptions cause the ozone to thin out or grow thicker.
"We found that the concentration of bromine from natural, very short-lived organic compounds is critically important," Klobas said. "Even small, part-per-trillion changes in the amount of bromine from these sources can mean the difference between a late 21st century volcanic eruption resulting in ozone column depletion or ozone column enhancement."
Why does this matter for Southeast Asia? Countries like Indonesia sit on the Ring of Fire—a band of the Earth prone to volcanic eruptions. Nearly every massive volcanic eruption in the last 11,700 years occurred somewhere in the Ring of Fire.
Indonesia alone has dozens of volcanos—many of which are active today. Mount Sinabung started erupting again only weeks ago. If there is another large-scale volcanic eruption sometime in the near future, the odds are pretty high that it will happen somewhere on the Ring of Fire.
Or maybe it won't. The science of when super-volcanos erupt is pretty rough. Some studies suggest that these kinds of eruptions can happen more than once a millennium. One particularly grim study suggested that we have a 1-in-10 chance of witnessing an eruption on-par with Tambora in the next 50 years, according to a report in the Guardian.
So will the next Tambora be in Indonesia? Who knows. But all these active volcanos won't be the culprit. According to scientists, it's the silent, sleepy volcanos we need to watch out for, the kinds of massive magma calderas building pressure for centuries at a time.
Is there anything we know for sure? Yeah, that all those cans of hairspray emptied out in the 70s and 80s are going to haunt us for years to come.