Rain clouds rarely cross the altitude of 10,000 feet but a “30,000 foot view” sets the context well for this post :)
It wasn't long ago when the Supreme Court of India had instructed the Delhi Government to consider “seeding” clouds over Delhi to induce rains in order to control the alarming pollution levels in and around Delhi. Since India had only deployed cloud seeding occasionally, and that too in the distant past, the term “cloud seeding” triggered a lot of conversations. What is cloud seeding? Does it really work? If it does work, then why has it not been used more extensively in areas that have face water crisis frequently? On the other hand, more recently, when the Dubai floods disrupted life and travel for masses, many jumped to the conclusion that cloud seeding was to be blamed.
Climate change is expected to impact the weather patterns across the world in ways that might not necessarily be conducive to the life of impacted population. Therefore, cloud seeding and other forms of weather engineering could become a part of our lives.
Before we pour over cloud seeding, let’s understand the difference between Climate Engineering and Weather Engineering. Climate engineering deals with global-scale, longer term climate interventions, while weather engineering focuses on localized, and point in time, atmospheric modifications.
Weather Engineering refers to interventions that influence local weather conditions for a certain period of time. It is limited both in terms of time and region of influence unlike other interventions like afforestation or climate engineering.
For centuries, people have looked to the sky in awe and wonder, with powerful storms and life-giving rains seen as messages or acts of a higher power. Both Zeus in the Greek mythology and the Dragon King in ancient Chinese culture are rain gods. Droughts and floods were unpredictable forces, beyond human control.
Weather engineering challenges that age-old belief. By tinkering with the atmosphere, it pushes the boundaries of what we thought possible. No wonder it can spark questions about whether we're venturing into godlike territory, trying to control something that was seen as bigger than humans.
Apart from cloud seeding, fog dispersion and hurricane modification are also examples of weather engineering.
Cloud Seeding
How it began - The story begins in the 1940s with Vincent Schaefer, a curious scientist who, while researching airplane icing, discovered that dry ice (frozen carbon dioxide) could trigger the formation of ice crystals in clouds. This revelation sparked the idea: could we use similar materials to nudge clouds into producing more rain or snow?
What it is - Air around us has water vapor/ moisture that leads to humidity. When water vapor in the air condenses into liquid, it becomes visible and leads to formation of clouds.
How it is done - Cloud seeding can be conducted in two main ways:
Static Cloud Seeding: This method involves introducing ice nuclei, like silver iodide or dry ice, into cold clouds with supercooled liquid water droplets. The ice nuclei trigger the formation of ice crystals or snowflakes, which grow and fall as precipitation.
Dynamic Cloud Seeding: This method aims to induce rain by boosting vertical air currents. It involves releasing fine particles of hygroscopic materials, such as salts, through flares or explosives into the base of warm clouds. These particles act as cloud condensation nuclei, increasing the number and size of cloud droplets, enhancing cloud reflectivity, and stability.
Cloud seeding can be carried out using aircraft to release substances from below or above the cloud base, or through ground-based generators. Newer approaches, like those in the United Arab Emirates, involve using drones to deliver electric charges to stimulate rainfall.
The right “seed” can accelerate the condensation of the clouds and lead to rain. The quest for the perfect "seeding agent" has been a long one. Silver iodide, a chemical that mimics the structure of ice, became the go-to choice for many cloud seeding programs.
Cloud Seeding – How it works
How it has performed so far - Cloud seeding has become a controversial topic. Some hail it as a potential solution to droughts, like the one that plagued Beijing in the lead-up to the 2008 Olympic Games. Cloud seeding efforts aimed to clear skies and make the city more photogenic for the opening ceremony were met with mixed success. In 2023, the United Arab Emirates (UAE) took a unique approach, using cloud seeding to tackle air pollution in Pakistan. The idea was to increase rainfall and wash away pollutants clinging to the atmosphere. While the results were inconclusive, it showcased the potential for using cloud seeding for purposes beyond just precipitation.
Of course, tinkering with the weather isn't fool proof. In some cases, cloud seeding efforts haven't produced the desired results, or worse, might have even led to unintended consequences. E.g. in the American Midwest concerns were raised that cloud seeding might have inadvertently reduced snowfall in some other areas.
It is important to note that Cloud Seeding accelerates precipitation. It needs enough water vapor to make rain happen. It cannot create water. So, areas that are arid may not benefit as much from Cloud Seeding.
Does it actually work? It’s been nearly 80 years since cloud seeding was initially discovered. Despite several trials across US, Australia, China, UAE, Israel and India, why is there still a debate on its efficacy and impact? The answers are clouded by uncertainty and it’s been hard to get from the fluff to the facts :).
Repeatability In some cases, scientists have observed that previous studies and conclusions were not replicable. A carefully designed randomized experiment was conducted from 2013 to 2020 in northern Israel. A unique feature of the design was the measure of rainfall on target, rather than rainfall in an unaffected area. The results were disappointing and led to a decision by the Israel Water Authority to stop operational seeding. (Source: https://doi.org/10.1175/JAMC-D-22-0077.1) On the contrary, previous experiments had shown ±20% increase in rainfall with cloud seeding, however with a different type of control.
Experimental Conditions What are ideal conditions for cloud seeding? This is one of the most important questions to help make cloud seeding more predictable and effective. However, as we all know weather phenomenon have many interacting factors which make it hard to predict. With the advances in technology and easy availability of drones, scientists are trying to establish more detailed protocols around what parameters should be tracked and optimized for better results.
In a recent study in the Western Ghats region in India, scientists were able to demonstrate that cloud seeding can be approached scientifically to reduce uncertainty. In the study, scientists made 5,000 cloud passes using two instrumented aircrafts and latest sensors to identify the exact conditions suitable for cloud seeding e.g. stage of cloud formation – that are key to creating more predictable experiments in the future. (Source: https://doi.org/10.1175/BAMS-D-21-0291.1)
The other forms of weather engineering that have been proposed, but haven’t been deployed frequently or are unproven include:
Fog Suppression- Foggy mornings can disrupt flights. Here, weather engineering comes to the rescue in the form of fog suppression. Studies suggest that certain sound waves (low frequency), can knock the fog. The sound waves disrupt the water droplets that make up fog, causing them to clump together and fall as drizzle.
Hurricane Modification: This technique is still under development, but the idea is to weaken hurricanes before they wreak havoc on coastal areas. Planes would fly into storms and drop materials like silver iodide. These materials could create more ice crystals within the hurricane, which can weaken the storm.
Issues with Weather Engineering
While one can understand the benefits that come with Weather Engineering, it would be important to spend a moment to understand the related issues. Firstly, it is a young science and there is a lot to learn. How often have you looked at the weather forecast only to be surprised the next day? Secondly, there are social, geopolitical and ethical issues that are tied with Weather Engineering.
Who owns the rain? Techniques like cloud seeding are local but the rains might not follow manmade boundaries. If the rains benefit or hurt others, who takes credit or the blame?
Downstream challenges – Rain in one area often will lead to water runoff which could lead to unintended challenges, especially if it is across geographical boundaries.
Playing Robinhood? – Would cloud seeding in one area essentially "steal" moisture from clouds that would have otherwise rained in neighbouring regions, leading to decreased rainfall there? Interestingly, there are mixed theories on this. While conventional theories did suggest that cloud seeding was stealing moisture, recent studies suggest a more nuanced and different picture. Apparently, the trigger to rain induced by cloud seeding invigorate the cloud system leading to more efficient precipitation process that can even squeeze extra moisture out of the air, potentially benefiting a wider area. The fact that the opinion is still divided on this should make us pause and appreciate how little we know about the weather systems - a giant, complex mix of air, water, and sunshine, swirling around the planet.
Can Cloud Seeding be a permanent solution?
That’s perhaps a billion-dollar question - can it be a reliable, long-term tool for managing precipitation. The answer, unfortunately, is complex. While the concept holds promise, the scientific community is still grappling with questions about its effectiveness and long-term impacts.
Besides the issues highlighted above, here's why long-term cloud seeding is challenging:
Variable Success: Cloud seeding works best under specific atmospheric conditions and with particular cloud types. These factors can vary greatly across regions and seasons, making it difficult to guarantee consistent results over an extended period.
Limited Data: While research is ongoing, the long-term ecological and environmental impacts of cloud seeding are not fully understood. Large-scale, long-term studies are needed to assess potential consequences on weather patterns, ecosystems, and water quality. Imagining weather as a giant, complex mix of air, water, and sunshine, swirling around the planet helps me in appreciating the complexity and scale of the system.
Imagining a giant glob of air, water and sunshine helps in appreciating the complexity of the system!
The Domino Effect: Seeding clouds in one area might influence precipitation patterns in neighbouring regions. The long-term implications of these potential disruptions to larger weather systems require careful consideration.
However, there are glimmers of hope. Long-term cloud seeding programs in some mountainous regions, like the Sierra Nevada in the US, have shown promising results in increasing snowfall. These projects, coupled with ongoing research, are helping scientists refine seeding techniques and understand the long-term viability of cloud seeding in specific contexts.
The future of cloud seeding likely lies in a targeted approach. It may not be a one-size-fits-all solution for global drought, but it could become a valuable tool in specific situations, like supplementing water supplies in arid regions or managing snowfall in critical watersheds. As research progresses and our understanding of the atmosphere deepens, cloud seeding might evolve into a more reliable and responsible technique for influencing weather patterns for the long haul.
Being cautious, yet optimistic -
We haven’t been the best at understanding the indirect effects of our actions (as in cases of DDT, CFCs, Green House Gases and Asbestos to name a few), so many scientists are rightly sceptical about deploying aerosols in atmosphere to engineer the climate. Even with more temporary, and seemingly more benign, weather engineering approaches, there's a lot to learn. Cloud seeding, for instance, might work wonders in one region but fizzle out in another. Like with Climate Engineering, it too could lead to nth order unintended issues. For e.g., accidentally trigger floods or disrupt natural weather patterns trying to make rain.
However, this has rarely stopped people form experimenting with things. A lot of research, supported by data from deployments around the world and advanced weather monitoring systems, will likely improve our understanding of the weather systems. So, it is likely that in years to come, as water security and containing impacts of climate change becomes a key political agenda, countries will start adopting such measures more frequently. Cloud Security could take on a completely different meaning then!