Clearing the Air: An Analysis of Weather Modification, Old and New
- Tom Wolfe
- 2 days ago
- 7 min read
In the 90th Legislative Session and beyond, Texas should stand firm against any ban on weather modification.
There is growing public awareness about humanity’s ability to influence the weather, specifically through cloud seeding (cloud seeding) and solar radiation management (SRM). Each of these two technologies involves dispersing substances into the atmosphere to induce a desired outcome. The respective goals of cloud seeding and SRM are to increase the precipitation that falls from clouds and to offset the warming of the planet. Cloud seeding and SRM are distinct subjects with important differences: cloud seeding is almost 80 years old and has been used around the world, whereas SRM is an emerging technology that has never been deployed on a large scale. Additionally, SRM typically seeks a global effect, whereas cloud seeding’s effects are localized. Despite these differences, SRM and cloud seeding are sometimes grouped together under an umbrella label, such as “weather modification.”
Clouds are a combination of tiny particles called aerosols and water (in whatever form) that has attached to them. Clouds contain water droplets and/or ice particles that are so small that they are too light to readily fall from the sky as precipitation, or fall so slowly that they evaporate while still high in the sky. Thus, clouds may hold a great deal of moisture without precipitation occurring. Cloud seeding aims to increase precipitation by injecting aerosols- typically salts or silver iodide- into clouds to cause droplets and ice particles to become heavy enough to fall to earth. Evidence indicates that cloud seeding generates a modest but meaningful increase in precipitation, perhaps a 5-15 percent increase over the baseline precipitation that would have otherwise occurred. But even a small percentage increase over a large area can yield many more acre-feet (AF) of water.
SRM makes use of aerosols as well, but in a different way. In the most commonly proposed form of SRM, solar aerosol injection (SAI), sulfur dioxide would be released high into the atmosphere (perhaps 20 kilometers high) by specialized aircraft (or perhaps balloons), where it would convert to aerosols known as sulfates. These light-colored sulfates reflect some sunlight back to space, preventing it from reaching earth’s surface and thereby inducing a cooling effect. While SRM has never been tested on a large scale, two real-world occurrences support its feasibility for cooling the planet. First, large volcanic eruptions that eject many tons of sulfur dioxide high into the atmosphere have a well-known global cooling effect. Second, humanity has “accidentally” deployed a form of SRM in the form of industrial sulfur dioxide emissions. These emissions are pollutants and fortunately have declined significantly since the 1970s; however, they ironically provide a benefit because the resulting sulfates reflect some sunlight that would otherwise reach the Earth’s surface. This inadvertent use of SRM has partially offset some warming of the planet.
The other commonly proposed form of SRM is marine cloud brightening (MCB), which has some similarity with cloud seeding. MCB envisions a large fleet of ships in the world’s oceans spraying a mist of saltwater into the lower atmosphere, where the salt particles would serve as “landing pads” on which water attaches to form droplets. MCB is premised on the fact that, all else being equal, clouds with a higher droplet concentration are more reflective. By increasing the number of droplets in a cloud to the appropriate concentration, MCB would cause the clouds to reflect more sunlight back to space, thereby cooling the planet.
The concept of SRM has been discussed in scientific circles since at least the 1960s, but the first field tests of SAI and MCB were not done until 2008 and 2011, respectively. No form of SRM has ever been tested on a large (i.e. non-localized) scale. In contrast, cloud seeding was discovered in 1946 and the first real-world testing was done the following year. Cloud seeding has been used by many countries and by a number of western states in the U.S. for decades. For example, its use in Texas started in the 1950s, and the state passed a statute governing it in 1967. Cloud seeding in the state leads to an additional 3 million AF of water annually. Today, over 50 countries utilize cloud seeding, with China having become the world’s most active practitioner of it.
The obvious benefit to cloud seeding is increased precipitation. Evidence indicates that cloud seeding actually increases precipitation, perhaps even in adjacent areas; it does not “steal” precipitation from other places. As the most recent Texas state water plan detailed, Texas faces a growing population and declining aquifers in the coming years; thus, anything that can increase water supply should be of interest. Studies in Texas and North Dakota have found substantial benefits of cloud seeding for agriculture. Intriguingly, cloud seeding can also be used for hail suppression, a potentially significant benefit to Texas given that the state suffers more major hailstorms than any other state. Hailstorms can cause billions of dollars in damage annually and are a key factor in why property and casualty insurance premiums in Texas have soared in recent years.
Earth’s average surface temperature has increased by about 1.1 degrees Celsius since the 1850-1900 period. Some researchers and policymakers attribute this to human emissions of greenhouse gases such as carbon dioxide, and urge action to combat it. Many analyses have found that a forced transition to a carbon-neutral world would have staggering costs, and real-world experience accords with them. Such a transition would be particularly difficult for Texas, given the prominent role that traditional energy companies play in the state’s economy. Continued innovation consistent with a free market may make a transition over a longer timeline economically feasible, as suggested by how prices have fallen for electric vehicles and solar panels. But there is a strong movement in some quarters to undertake a rushed or forced transition, and the possibility that policymakers- particularly at the federal level- will be sympathetic to this view cannot be dismissed. The potential benefit of SRM is that the cost to deploy it would be far less than the costs of forced transition; estimates range from several billion dollars a year to perhaps $40 billion annually.
Because real world testing of SRM has been very limited, there is uncertainty about the effects of a large-scale deployment. SRM carries significant theoretical risks, depending on the type of deployment and particles used, including possible changes in the ozone layer, increased pollutants in the air, uncertainty about the effects of abruptly ceasing SRM, and most importantly, the possibility of “domino effects” on global weather, such as reduced precipitation. These risks vary depending on the deployment approach, though more analysis and policy would be needed to more fully understand and mitigate these impacts. But SRM’s benefits must be considered with these risks to calculate the net effect of SRM. If SRM is properly regulated, its deployment in the near future can be limited to small-scale field testing that does not meaningfully affect the weather, but provides scientists with more data to better understand whether it would ever be feasible on a large scale. One can support field testing of SRM on a scale that is too minor to affect climate but still provides valuable insights, while being firmly opposed to using SRM to induce cooling of the planet unless and until it is better understood.
Beyond a requirement that weather modification operators report their activities to the government, there is no federal regulation specific to weather modification, and binding international regulation is similarly lacking. Western states that use cloud seeding have statutes governing it, but Texas law addresses only cloud seeding, not SRM.
Recently, several states have banned weather modification, and bills to that effect have been introduced in many other states and in Congress. These well-meaning efforts are misplaced. Cloud seeding offers key benefits such as aquifer replenishment, improved agriculture, and hail suppression. Moreover, in contrast to SRM, cloud seeding carries little risk. It has been used for decades without any sign of environmental problems, and the silver dioxide often used in it does not create soil or drinking water concentrations that are concerning. China has become the dominant global player in cloud seeding, and ceding the field to the U.S.’s most powerful rival weakens the U.S. economically and creates national security concerns.
A ban on SRM testing would also be a flawed approach. A middle path is available: regulating SRM and allowing testing on a limited scale that does not meaningfully affect the weather. A country or state banning SRM would do nothing to protect itself from SRM if a different government (e.g., China) deployed it, because SRM’s effects do not stop at borders. Just as with cloud seeding, a ban on SRM would create serious national security concerns. The federal government has recognized the threat that a country or organization unilaterally deploying SRM could pose to the U.S. This threat could take at least two forms. First, unilateral deployment could well trigger significant disputes between nations. Second, allowing other countries to control this globally significant infrastructure and intellectual property cedes American leadership.
Economic considerations also argue against a ban. Proponents of the hypothesis that humans are causing warming of the planet often urge the enactment of policies with potential for catastrophic economic effects, such as a rapid transition to a carbon-neutral world via command-and-control regulation. The chance of such a “crash transition” increases in the absence of other options like SRM that could allow for an innovation-driven transition instead. Texas is the energy powerhouse of the world and traditional energy companies are a key reason for that; thus, a crash transition would be especially economically harmful to it. But much regulation of the oil and gas industry occurs at the federal level. It is certainly possible that future policymakers will argue that there is a need for a crash transition that would harm Texas industries. It would be better to have options on the table that could manage potential climate risks in other ways, like SRM, rather than driving an uneconomic transition. Having a well-researched technology that could be rapidly deployed at a vastly lower cost could be prudent.
SRM is controversial in the scientific community. But as private companies and governments have begun to provide financing for planned SRM activities, there has been a growing call for international regulation of SRM. Policymakers should anticipate an international debate on this subject in the near future. A ban on SRM in the U.S. or Texas would not stop SRM research and development, but simply drive it to other countries. Without an advanced understanding of the benefits and risks of this technology, a government will be ill-equipped to advance its interests in the forthcoming debate.
