On June 15, 1991, the world’s largest volcanic eruption of the century occurred in the Philippines, emitting an immense amount of ash and gas. The volcano, Mount Pinatubo, released a tremendous fifteen million tons of sulfur dioxide into the stratosphere, the second major layer of the Earth’s atmosphere. When in the atmosphere, sulfur dioxide typically reacts with water molecules, creating aerosol particles primarily composed of sulfuric acid droplets.

These particles disperse and absorb sunlight which, as a result, cools the surface of the Earth. In the case of Mount Pinatubo, the earth cooled as much as a degree fahrenheit for a duration of about two years. The event has allowed scientists to investigate further possible solutions to alleviate the effects of global warming by using the observations of the eruption as an underlying base.

In the spring of 2019, Harvard scientists will be conducting an experiment, called the Stratospheric Controlled Perturbation Experiment (SCoPEx). The scientists behind this experiment, David Keith, Zhen Dai, and Frank Keutsch, plan on injecting sun-dimming particles into the Earth’s atmosphere. This would ultimately mimic a volcanic eruption, where massive amounts of the same particles are released into the atmosphere. Despite how bizarre the idea sounds, it could minimize large-scale global warming in the future.

The experiment itself is in no way harmful as, “the release of experimental materials will be small compared to the release of the iron filling ballast that are commonly released to control the altitude of stratospheric balloons.” This experiment will be the first solar geoengineering project to be conducted outside of a scientific laboratory. Solar geoengineering, also called solar radiation management (SRM) is a technique which focuses on artificial cooling of the planet by reflecting sunlight back into space.

“Even if global temperatures do drop by a couple of degrees, this will only buy us time to pursue global-scale emissions reduction,” said Alysa Chen ’19.

For the first phase of the experiment, the scientists will launch two balloons, containing 0.5 micrometer carbon carbonate particles, twenty kilometers into the stratosphere (the layer where the ozone layer is found). Rather than utilizing sulfur dioxide, which depletes the ozone layer, the experiment will be using calcium carbonate, a nontoxic chemical found in common household items. As soon as the calcium carbonate is released, the balloon will be used to observe the dispersion of the particles in the atmosphere.

Injecting stratospheric aerosols on a larger scale may come with potentially detrimental consequences. For instance, the aerosols would only reflect sunlight, not greenhouse gases, consequently allowing the oceans to become more acidic. “Manipulating our atmosphere will only cause temporary relief from high global temperatures, and it will deviate attention and money away from emission reduction and to temporary solutions such as building sea walls and carbon sequestration instead,” said Alysa Chen ’19. Carbon sequestration, also under the category of geoengineering, is a process of removing carbon dioxide from the atmosphere and turning it into solid or liquid form. However, artificial carbon sequestration is more costly than solar geoengineering.

“Even if global temperatures do drop by a couple of degrees, this will only buy us time to pursue global-scale emissions reduction, which, if done aggressively in time, will provide lasting climate change mitigation. Until then, more research should be done to investigate the drawbacks of solar geo-engineering, while most of the money should be used to transition the world’s energy sources to renewable energy,” said Chen.

Despite the consequences that may come with manipulating the atmosphere, the SCoPEx experiment may be a way for scientists to explore the undiscovered aspects of solar geoengineering. As global warming becomes a growing concern, scientists have been researching ways to lessen the detrimental effects of rising temperatures. “If there are any experiments that run a chance of minimizing the effects society has had on the atmosphere, they most definitely should be researched as much as possible until we find a suitable solution,” Amelia Volpe ’21 said.

“At this point, humans have caused a great deal of damage and it’s up to us to tackle that in any way possible,” said Volpe.