When NASA isn’t blasting off rockets, hypothesizing about aliens or dreaming up ways for humans to survive on Mars, some of the most critical issues the space agency investigates are right here on Earth.
Emissions that deplete the ozone layer continue to be of more concern as chemicals unleashed into the air keep eating away at our planet’s built-in SPF. Now atmospheric scientist Quing Liang and his team of researchers have published a study in Science that investigates the effects of short-lived and long-lived compounds threatening stratospheric ozone—and how we can effectively prevent it from vanishing any further or even reverse the damage.
“Reactive halogen gases containing chlorine or bromine can destroy stratospheric ozone via catalytic cycles,” Liang and colleagues said. “The main sources of atmospheric reactive halogen are long-lived [substances], all of which persist in the atmosphere for years.”
NASA’s Goddard Earth Observing System Version 5 (GEOS-5) model gives researchers a simulated 3D view of the atmosphere that allows them to follow potentially harmful gases as they ascend. The United Nations Environment Programme’s Montreal Protocol has outright banned or is at least phasing out longer-lived substances that can survive long enough to devour the ozone layer. While there have been fewer emissions of corrosive long-lived chlorine and bromine (mostly released before 1987) since the mid-1990s, shorter-lived compounds that are still unregulated have recently come under scrutiny. They may linger in the atmosphere for under six months, but have been a looming concern since more emissions have been escaping into the atmosphere.
Dichloromethane is one of these compounds. While it breaks down in several months and has been used successfully as a substitute for many chemicals on the UN’s banned list, rising emissions have some scientists concerned even though any of the harmful traces it leaves behind are completely gone in a few years. Liang believes there is no reason for paranoia since the economic demand that influences dichloromethane-dependent industries will eventually reach its upper limit. Similar substances emitted on land usually break down before they can even reach the stratosphere.
"Because of its very short-lived nature, and the unlikely scenario of the emissions sustaining a high growth rate, it’s highly unlikely dichloromethane would have a major impact on the ozone layer," he assured.
It’s the short-lived bromine compounds we have to worry about. Global warming has resulted in more of these rising from the ocean surface and riding tropical thunderstorms to the stratosphere in less time than it takes for them to degrade. As ocean temperatures increase, so will these emissions, which spend most of their lifespans eating away at ozone.
Another factor in ozone depletion that is making scientists nervous is continued breaching of the Montreal Protocol. Banning obviously doesn’t have a hundred percent success rate, which is obvious when some of the ozone’s worst enemies, like carbon tetrachloride. Even keeping the UN’s eyeball on highly volatile carbon tetrachloride emissions doesn’t account for it emerging as a by-product of chloroform and dichloromethane production.
While most of us don’t have access to NASA’s 3D simulators, this might drastically change how you read labels from now on.