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Most real-world experiments with direct relation to Stratospheric Aerosol Injection (SAI) are canceled due to public pressure and controversy.

Summary​

Stratospheric Aerosol Injection (SAI) research faces significant barriers to real-world experimentation due to public opposition and ethical concerns. Nearly all physical experiments have been halted, with studies limited to computer modeling. Primary objections center on the 'moral hazard' argument - the fear that SAI's potential as a climate intervention might undermine efforts for other essential emissions reductions. Two notable canceled projects include the UK's SPICE experiment (2011-2012), which proposed testing aerosol delivery methods via balloon, and Harvard's SCoPEx initiative (2014-2024), designed to study aerosol effects on ozone and atmospheric dynamics. Both projects faced opposition from scientific communities, environmental activists, and indigenous groups, ultimately being halted due to policy conflicts, patent disputes, and ongoing controversies about geoengineering's risks and societal implications.

The highly contentious nature of SAI has resulted in almost no real-world experiments being carried out to explore its viability as a tool for climate change adaptation. Intense pushback from researchers, activists, and some indigenous groups has relegated the majority of SAI research to the realm of computational climate modeling. This is mostly due to the perceived moral hazard that the availability of SAI as a potential "quick fix" could reduce the urgency of efforts to reduce greenhouse gas emissions and transition to sustainable energy sources, which could lead to a reliance on SAI as a stopgap measure, delaying the necessary systemic changes needed to address the root causes of climate change. The environmental risks of experimentation are also a reason for the resistance to experimentation; however, most proposed experiments attempted to utilize mostly inert particles that would be released in relatively minuscule quantities. The two largest attempted physical experiments relating to SAI are SPICE and, most recently and controversially, SCoPEx.

SPICE (Stratospheric Particle Injection for Climate Engineering)​

The SPICE project was a collaboration between four of the United Kingdom's largest universities that sought to answer three pressing questions relating to SAI 1:

  1. What type and quantity of aerosols would be required to safely manage the climate system?
  2. What would be the best method of delivering these into the atmosphere?
  3. What would be the consequence of this injection of aerosols into the atmosphere?

The SPICE project encompassed computational modeling and lab analysis of aerosol feasibility; however, it was their proposed real-world experimentation that received the most pushback and was eventually canceled. SPICE attempted to attach a hose to a balloon that would float one kilometer above ground level, which would spray a mist consisting of 150 liters of water.

In 2011, the project was put on hold due to pushback from environmental groups as well as concerns that the experimentation would violate the UK's commitment to not conduct large-scale geoengineering projects 2. The experiment was finally canceled in 2012 due to patent concerns involving the delivery method 3.

Stratospheric Controlled Perturbation Experiment (SCoPEx)​

SCoPEx was an attempted experiment conducted by Harvard University, which was first envisioned in 2014. The project aimed to utilize a high-altitude balloon carrying measuring instruments, which would rise to approximately 20 km in altitude in the lower stratosphere. Once there, a small amount of sulfate aerosols would be released via a propeller (no greater than 2 kg) to cover a 'seeded' area 100 m in diameter and 1 km long. Afterwards, the balloon would return to the seeded area and lower instruments down into the aerosol plume. The main goals of the experiment were 4:

  1. Measure the catalytic effects of sulfate aerosols on ozone depletion.
  2. Measure the effects of sulfate aerosols on water vapor dynamics in the stratosphere.
  3. Advance the knowledge of direct experimentation in the lower stratosphere.

In 2019, the project paused to evaluate the controversy surrounding the project, which similarly revolved around the perceived moral hazard. In 2021, attempts were made to move the project from Arizona and New Mexico to Sweden. But in March of 2024, the project was finally canceled by the Vice Provost for Research and the Vice Provost for Climate and Sustainability 5.

Sources​

Footnotes​

  1. SPICE Project. (2024). Stratospheric particle injection for climate engineering. http://www.spice.ac.uk/ ↩

  2. Harris, M. (2011, September 22). SPICE put on ice. Nature News Blog. https://blogs.nature.com/news/2011/09/spice_put_on_ice.html ↩

  3. Cressey, D. (2012). Geoengineering experiment cancelled amid patent row. Nature. https://doi.org/10.1038/nature.2012.10645 ↩

  4. Dykema, J. A., Keith, D. W., Anderson, J. G., & Weisenstein, D. (2014). Stratospheric controlled perturbation experiment: A small-scale experiment to improve understanding of the risks of solar geoengineering. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 372(2031), Article 20140059. https://doi.org/10.1098/rsta.2014.0059 ↩

  5. Jinnah, S., Bedsworth, L., Talati, S., Gerrard, M. B., Kleeman, M., Lempert, R., Mach, K., Nurse, L., Patrick, H. O., & Sugiyama, M. (2024). Final report of the SCoPEx advisory committee. Harvard University. ↩