Can We Engineer the Weather?

Exploring the Scientific Challenges of Local and Global Weather Modification

Cloud seeding is a form of weather modification in which chemicals, usually silver iodide, are dispersed into clouds to induce or enhance precipitation which I have discussed here. Cloud seeding, in particular, involves the introduction of substances into the clouds to encourage precipitation or clear skies downwind. The process relies on the fact that certain particles, for example, silver iodide, have a similar crystalline structure to ice, which allows them to act as a nucleation site for the formation of ice crystals in supercooled clouds. These ice crystals then grow and fall as rain or snow, depending on the temperature. Let’s examine the most well-known cloud seeding project and the potential for global geoengineering through cloud seeding.

The cloud seeding project undertaken for the 2008 Beijing Olympic Games was one of the most publicized examples of weather modification in recent history. The Chinese government embarked on this ambitious endeavor with the aim of ensuring clear skies for the opening ceremony of the Olympics. The technique used during the Beijing Olympics aimed at ensuring that any rainfall would occur before the events or upwind and miles away. This involved the deployment of rockets and airplanes to seed the clouds with chemicals such as silver iodide, which encourages cloud condensation and precipitation.

“We fired a total of 1,104 rain dispersal rockets from 21 sites in the city between 4 p.m. and 11:39 p.m. on Friday, which successfully intercepted a stretch of rain belt from moving towards the stadium” – Guo Hu, Beijing Municipal Meteorological Bureau (BMB).

Source: https://www.wsj.com/articles/BL-CJB-347

However, this event also serves as a focal point for broader discussions on the effects of geoengineering, particularly in terms of its global implications. While the endeavor was hailed as a success by some, it also raises significant concerns and skepticism about the broader implications of such geoengineering efforts.

Opening ceremony of the 2008 Olympic Games on a clear night in Beijing, China. Source: https://www.latimes.com/sports/la-olympics-photos-2008-pg-photogallery.html

Same stadium on a smoggy day. Source: https://www.engineering.org.cn/en/10.1016/J.ENG.2016.01.029

Attributing clear skies solely to cloud seeding is problematic, as is attributing weather events to climate chnage. Weather patterns are inherently complex, influenced by numerous factors beyond human control. While China reported increased precipitation in targeted areas upwind of Beijing, it's impossible to definitively isolate the effects of their project from natural weather variability.

Geoengineering, the deliberate large-scale intervention in the Earth's natural systems to affect climate, encompasses a range of techniques, including cloud seeding, carbon dioxide removal, and solar radiation management. Cloud seeding, as discussed above, involves the introduction of substances into the clouds to change local weather patterns… But does it have the potential to change the global climate?

Let’s imagine that every aircraft flying today was spraying the entire contents of its fuel tanks into the atmosphere… yes, that’s ridiculous but it’s merely a thought experiment. The number of airplanes flying around at any given time is approximately 10,000 airplanes.

The average fuel capacity per aircraft varies significantly depending on the airplane's size and type. A large commercial airplane like a Boeing 747 can hold around 200,000 kg of fuel, while a smaller regional jet might hold around 10,000 kg. Let’s just assume an average fuel capacity of 100,000 kg per airplane (a very rough estimate), the total fuel mass would be: 10^9 kg or 1,000,000,000 kg.

Let’s compare this figure to the mass of the atmosphere which is 5x10^18 kg or roughly 500,000 times greater. I often hear how CO2 can’t have an enormous effect on the surface temperature as it only represents 400 parts per million of the atmosphere. I don’t find this argument very convincing as very small amounts can have enormous effects, look at fentanyl for example.

Now let’s compare our thought experiment concentration to that of present-day CO2. Given some assumptions, we can attempt to calculate a hypothetical ppm for our cloud seeding material.