how birds flew to predict the weather. Since then, the science of meteorology has helped us identify more precise tools for weather prediction. But it seems, human ingenuity has already broken another barrier: we are no longer only able to predict weather but we can also modify it almost at will! The science behind weather modification is not particularly new with experiments already taking place in the 1960’s but more recently we have seen examples of weather modification in practice. For example, China was gearing up to deploy weather modification techniques during the course of the Olympic Games it would host to ensure there would be no rain, while in 2009 the Chinese air force claimed to have conducted the biggest weather modification operation in the country’s history to ensure clear blue skies over Tiananmen Square for the National Day parade¹.
Weather modification certainly appears to be a step too far – human hubris taking over and upsetting natural processes. But the reality is that many parts of the world are suffering from droughts and resource scarcity and some of these issues could be alleviated by weather modification. Crops and property damage could be saved through weather modification by preventing catastrophic weather events such as hail or hurricanes. Taken a step too far, weather modification would be used as means of aggression towards another country by provoking damaging weather; this is why weather modification in warfare has been banned by the United Nations².
Playing with the water cycle
The most common form of weather modification is cloud seeding to increase rain or snow, usually for increasing the local water supply. The technology has been controversial ever since it was invented by Vincent Schaefer, a chemist for General Electric, in 1946. Schaefer made the first snowstorm in a laboratory freezer using dry ice to form crystals and later on developed a compound, silver iodide, that increased the size of water droplets and induced rain and snow indoors; but just like today doubts about the impact of meddling with nature quickly emerged³,⁴.
Cloud seeding relies on our knowledge of how cloud forms and the conditions under which precipitation happens. Leveraging this knowledge and the use of chemicals, weather modification companies can increase the possibility of rain by deploying those chemicals in specific location. More specifically, there are two types of seeding agents that can be used depending on the clouds being treated. There are two primary cloud microphysical processes that produce precipitation: “cold rain” which develops through a process that involves ice particles and “warm rain” which develops through a process that is entirely liquid⁵. So seeding agents are tailored to either of those processes.
The most common agents used in “cold rain” are silver iodide and dry ice (frozen carbon dioxide). To deploy them, pyrotechnic flares usually contain silver iodide or a salt are installed on an aircraft while a solution containing silver iodide dissolved in acetone is dispensed via combustion from devices called silver iodide (ice nuclei or aerosol) generators. These generators can be located on the ground or attached to the wings of an aircraft. Dry ice is usually acquired in pellet form and placed in special insulated containers; most frequently dry ice is dispensed from the aircraft⁵.
Similarly, “warm rain” cloud seeding agents can be produced by “hygroscopic” flares which contain some type of salt and when burned, they produce minute particles of the salt which attract water vapor, forming cloud droplets in addition to those already present in the cloud.
According to the Weather Modification Association, these processes and materials are safe for the environment and do not use up natural resources that would otherwise allow for rain in a different place. But they accept that there is no way to guarantee 100% the success of a project to modify the weather. Indeed, a scientist at the US National Center for Atmospheric Research believes that research proves that the effects of cloud seeding cannot be accurately estimated: the Center’s own research—a nine-year, $14 million government-funded study in collaboration with WMI and the University of Wyoming— found that seeding increased snowfall 5 percent to 15 percent from clouds in two Wyoming mountain ranges⁴.
But cloud seeding is not only one of the weather modification technologies that have been developed. Another type of weather modification that has been used aims to minimise the impacts of hurricanes and tropical cyclones. Several projects looked into this: Project Stormfury supported by the US government between 1962 and 1983 involved flying aircraft into storms and seeding the eyewall with silver iodide whereas a similar project using soot was run in 1958, with inconclusive results. Since then, various other theories have been proposed to reduce the harmful effects of hurricanes but Florida company Dyn-O-Mat has proposed the use of a patented product it developed to reduce the strength of hurricanes. The substance is a polymer in powder form which reportedly can absorb 1,500 times its own weight in water so if dropped into clouds it could remove their moisture and force the storm to use more energy to move the heavier water drops, thus helping to dissipate the storm².
A lot of investment has gone into deciphering the physics of weather patterns and trying to emulate them. So despite the hurdles along the way, it is clear that weather modification is here to stay. For the moment it does not appear that humans have mastered the art of weather modification, but astounding progress has been made in terms of trying to enhance some weather features. But perhaps the question is not: are those technologies really changing the weather, but rather if they are how is it affecting our planet and are the potential impacts of using them cancelling out any benefit for the area in which they are deployed?