Geoengineering and Sulfur Dioxide: A potential coolant for our atmosphere?

Everyone has heard of brutal volcanic eruptions, such as Tambora or Krakatau. These volcanos, intuitively, release several kinds of harmful and dangerous chemicals into the atmosphere such as sulfur dioxide and acids. Recently, there was an underwater volcanic eruption of the Hunga Tonga–Hunga Ha’apai volcano in Tonga, a country in Oceania. This eruption released an unprecedented amount of water vapor into the atmosphere with the force of a nuclear weapon. The eruption happened over two uninhabited islands and it resulted in harms and benefits to the atmosphere in terms of climate change.

Hunga Tonga’s eruption could have resulted in the potential deteriorating of the ozone layer, a crucial part of the planet. Ozone, also known as O3, is a molecule that is abundant in the stratosphere, making up the ozone layer. It protects the life on Earth by absorbing 99% of all the UV light and radiation that comes from the Sun. Without the ozone layer, too much radiation would reach Earth and because of skin cancer, cataracts, the and the inability to grow food, it would be unable to sustain life on Earth. This volcano spewed gasses, aerosols, and sulfur dioxide as high as the stratosphere. Scientists determined due to the chlorine in the plume from the volcano reacting with water, the ozone layer might partially degrade.

One chemical Hunga Tonga and other volcanoes have released that has raised some discussion in terms of helping the climate is sulfur dioxide. Sulfur dioxide or SO2 is supposedly a natural cooler as it would reflect some of the Sun’s rays back into space. If sulfur dioxide were to be injected into the atmosphere, a lot of it would react and form sulfate, which would result in a net cooling effect of the Earth. Scientists have, so far, been unable to geoengineer sulfur dioxide in large amounts, which is why the eruption of Hunga Tonga–Hunga Ha’apai was so important — it gave scientists an opportunity to test their climate models and see the effects and potency of sulfur dioxide since there was so much of it in the plume from the volcano.

Sulfur dioxide causes things like acid rain and is extremely harmful and fatal to human beings, causing a variety of health problems and thousands of deaths per year. Scientists have known that maritime ships have been releasing it for several years. However if sulfur dioxide is distributed in the stratosphere, it is too far from us to actually cause any harm and provides us with the net cooling effect.

The flip side of the coin is that studies have found SO2 to have negative effects on the ozone layer, causing ozone depletion. According to a study done at Iowa State University, “SO2 depletes the ozone layer by reducing the solar flux because it absorbs 180 nm-390 nm. This is the same range for the photolysis of O2, which is necessary for ozone production. Since photolysis is reduced, ozone production is also reduced.” Further, not only does sulfur dioxide deplete the ozone layer, but, in a volcanic eruption, it also causes chlorine to be more reactive and degrade the ozone layer even further.

While sulfur dioxide can used as a cooling agent, when viewing it holistically, there are ultimately more harms than benefits as seen through the premature deaths, health problems, acid rain, and ozone layer depletion.

The eruption of the Hunga Tonga–Hunga Ha’apai volcano in 2022 provided a unique opportunity for scientists to delve into the complexities of volcanic emissions and their impact on our planet’s climate. While the release of sulfur dioxide from volcanic eruptions has sparked discussions about its potential role as a natural cooling agent, the consequences of such emissions reveal a delicate balance between benefits and harms. The eruption serves as a reminder that the intricacies of geoengineering, even when presented with a natural experiment, come with a myriad of consequences. As we grapple with the challenges posed by climate change, it is essential to approach potential solutions with caution and a comprehensive understanding of their long-term impacts, on the climate and the population. The eruption of Hunga Tonga–Hunga Ha’apai unfolds as a lesson in the interconnectedness of Earth’s systems, urging us to move find truly beneficial solutions to climate change, and not just cop-outs.