The idea that control of climate and weather belongs to the cosmos is age-old. In Greek mythology, the most powerful god of all, Zeus, was ruler of the skies and creator of storms. The three most important Mayan gods, Kukulcán, Itzamná, and Ix Chel, were masters of water, the sky, and the moon respectively. The god Ra of ancient Egyptian culture had domain over the sun and was considered to be the central deity of ancient Egyptian belief.

After thousands of years of churning wheels of progress, we may have reached a point where man will truly have control over the heavens. Geoengineering is an umbrella term to describe planet-wide technology that manipulates Earth’s climate to a certain end.  You might have heard about a branch of this greater field called solar geoengineering as a somewhat outlandish tactic to mitigate climate change. A hot button topic within climate action discourse, solar geoengineering has been described by some as a shortcut to prevent devastating damage due to the extreme temperature rises that global warming causes. Here’s how it’s supposed to work: reflective aerosols are released into the upper atmosphere, or the stratosphere, in order to deflect solar radiation back out into space and away from Earth’s surface, cooling the planet as a result.

Though this tactic may seem a little unfounded at first glance, the idea can be traced to the 1991 eruption of Mount Pinatubo in the Philippines. Speculated to be the largest aerosol disturbance of the stratosphere in the 20th century, Pinatubo injected a 20-million ton sulfur dioxide cloud into the stratosphere at an altitude greater than 20 miles. What followed was remarkable: over the next 15 months, global temperatures dropped by a maximum of 0.6ºC.

Talk about solar geoengineering had begun around the 1970s, but Pinatubo pushed the field to the forefront of climate conversation, and not only by “small fish.” Bill Gates, billionaire founder of Microsoft, has also begun investing in solar geoengineering research by leading thinkers of the field at Harvard University. As of 2017, the university’s scientists have been developing research on solar geoengineering through the Stratospheric Controlled Perturbation Experiment (SCoPEx) program. By spraying calcium carbonate (chalk) dust with a balloon across a small area and observing changes to the particles, the researchers hope to understand more about how aerosols change in the atmosphere over time. As of now, however, the data is very limited on what the effects of aerosol injection may be.

The work being done to develop solar geoengineering practices is described as commendable by some. An article published in May of 2021 by Nature titled, “Give research into solar geoengineering a chance,” argued for the potential benefits to be reaped from stratospheric aerosol injection (SAI) and marine cloud brightening (MCB), the two main types of solar geoengineering. However, proponents of these strategies have also received quite a bit of pushback from both climate experts and political scientists. While solar geoengineering is attractive in appearance as being a quick, relatively cheap fix to our warming problem, the disturbing lack of understanding of the technology sows a slew of potential pitfalls that would result from its institution. The effects of solar geoengineering on the water cycle are unknown, and some speculate that SAI could lead to major changes in rainfall patterns, conceivably causing grim consequences for crop yield.

Moreover, procuring 20 million tons of sulfur every year to maintain cooling would pose its own set of problems logistically, especially when considering how to distribute these particles efficiently and effectively.  Solar geoengineering would only solve the “warming problem”: it would not tackle the serious consequences of CO2 accumulation in the atmosphere, such as ocean acidification. Would the costs associated be worth reallocating from decarbonization? Ethically, would solar geoengineering de-incentivize investment in decarbonization? By the same token, the moral implications of solar geoengineering are concerning at best. The relative cheapness of solar geoengineering technology renders it incredibly easy to be geopolitically weaponized. Not only could the technology be used to cause mass droughts in certain regions of the world, but it could also exacerbate the vulnerability of certain populations to pollution and climate change. A marked increase in particulate matter in the atmosphere would likely have reverberations in human health.

Possibly most worrying of all, there is no current understanding on whether or not these forms of solar geoengineering would even have the intended effects on global temperature. While Mount Pinatubo did cause a drop in temperature, it’s eruption may just as easily have caused warming. During the 1991 eruption, the volcano pumped out a great deal of hydrogen chloride into the atmosphere, which was luckily washed out by a well-timed typhoon. Had the hydrogen chloride remained in the atmosphere, the ozone layer would have likely been significantly damaged by this influx of harmful aerosols. Ultimately, what effects would a massive injection of reflective aerosols have on the ozone layer? Even if the proposed cooling were to take place, a study by a group of Berkeley scientists shows that this would likely have no effect on crop yield. Looking at the yields of common crops like maize, soy, rice, and wheat after the 1991 Pinatubo eruption, the group determined that though the cooling benefitted crop growth, the aerosols also reduced incident solar radiation, essentially cancelling out the positive effects of the eruption on crops.

Nonetheless, solar geoengineering remains a promising and fascinating prospect for the mitigation of global warming. As research initiatives press on, the Union of Concerned Scientists proposes the installation of a set of crucial guidelines.

  1. That government-independent mechanisms be put into place to ensure that experiments are of high scientific quality with no risks in any regard.
  2. That experiments be highly controlled, small-scale, and equipped with rigorous safety measures.
  3. That funding coming from governments and other entities supporting only first-line climate change solutions.
  4. That there be an open line of communication between researchers and the government towards citizens: that the public be informed.
  5. That climate-vulnerable communities are heavily involved in discourse and decision-making surrounding solar geoengineering projects, especially communities directly affected by research.

Regardless of whether or not the choice to begin solar geoengineering our climate is wise, it may soon become our best option if our climate is not decarbonized appropriately to mitigate devastating warming. Will we make it in time to avoid this last-ditch effort to beat the heat? In what ways would solar geoengineering change our physical Earth and the global socio-political landscape?