Last updated by The POOG on January 04, 2021.

Exercises in weather modification by seeding clouds with a dispersion of silver iodide particles to induce rain or snow, have been carried out for decades. A number of chemicals have been used for this purpose[7]. Results may not be predictable and precipitating water in one place[8] may deny natural precipitation in another since atmospheric water vapour in an area in the short run is fixed.

Climate modification by dispersing chemicals in the upper atmosphere (stratosphere) is a different proposition. The current goal is to reduce global temperatures by dispersing chemicals to simulate volcanic cooling such as occurred in 2001-2003 due to the eruption of Mount Pinatubo[9]. The eruption cooled the earth’s atmosphere by a maximum of a of ~ 0.5 K 18 months later[10].

To implement this technology based on the false premise of anthropomorphic global warming as a threat that needs to be corrected is a colossal waste of money and may have serious and expensive downside. Should proponents be successful, they may in fact exacerbate the natural cooling that is expected with the next grand solar minimum (GSM) that we will entering by 2031 at the end of this 11-year solar cycle 25 which just began in 2020. NOAA has a nice scrollable table[11] of sunspot numbers which correlate to GSMs.

The Harvard Experiment – SCoPEx

Researchers at Harvard have proposed a test to observe the effects of dispersing a common mineral, calcium carbonate or limestone, in the stratosphere. Frank Keutsch[5] describes the purpose of the Stratospheric Controlled Perturbation Experiment (SCoPEx) as

to advance understanding of stratospheric aerosols … by making quantitative measurements of some of the aerosol microphysics and atmospheric chemistry required for estimating the risks and benefits of solar geoengineering …

Source: Keutsch[5].

The actual experiment is described as using a balloon platform

capable of injecting a small amount of aerosol (<1kg) at about 20km altitude preparing a plume with kilometer lengthscale and diameter of a few hundred meters. The propelled balloon will then be flown back through the plume to measure the temporal evolution of the perturbation resulting from the plume and study how the aerosol in the plume is developing.

Source: Keutsch[5].

A picture of the proposed balloon in flight is given by the Keutsch Group at Harvard.

Source: Keutsch Group Harvard.

The actual experiment will be carried out by Swedish scientists[6].

You may recall when the environmental movement pegged acid rain due to sulphur compound emissions from industrial and coal-fired power plants as the villain behind acid rain. When the Harvard gnomes start spraying similar compounds into the atmosphere – well they’re not going to stay up there.

Politics and Policy

David Keith of SCoPEx explains the project in the next video with its projected costs and policy implications.



  1. Williamson P, Watson R, Mace G, et al. Geoengineering in Relation to the Convention on Biological Diversity: The Technical,and Regulatory Matters. Secretariat of the Convention on Biological Diversity. ISBN 92-9225-429-4. September 2012. PDF.
  2. Harvard Project to Address Uncertainties in Solar Geoengineering. Harvard School of Engineering. July 29, 2019.
  3. Dykema JA, Keith DW, Anderson JG, and Weisenstein D, (2014). Stratospheric controlled perturbation experiment: a small-scale experiment to improve understanding of the risks of solar geoengineering. Phil. Trans. R. Soc. A.37220140059
  4. Keith, D.; Dykema, J. A.; Keutsch, F. N. Stratospheric controlled perturbation experiment (SCoPEx): overview, status, and results from related laboratory experiments. AGU. December 2017, 2017AGUFMGC43H1162K.
  5. Frank Keutsch. Stratospheric Controlled Perturbation Experiment (SCoPEx). SGRP. As of January 03, 2021.
  6. Doyle A. Planned Harvard balloon test in Sweden stirs solar geoengineering unease. Forbes. December 18, 2020.
  7. dwipurwa. 8 Chemicals Used in Artificial Rain – Cloud Seeding. AZ Chemistry. December 29, 2017.
  8. Moseman A. Does cloud seeding work? Scientific American. February 19, 2009.
  9. Staff. Global Effects of Mount Pinatubo. NASA. Acessed January 03, 2021.
  10. Soden BJ, Wetherald RT, Stenchikov GL, and Robock A. Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor. Science. Vol. 296. April 26, 2002. PDF.
  11. Predicted Sunspot Number and Radio Flux. NOAA. January 04, 2021.