To seed or not to seed? That is the question...behind weather pattern modification.

Image by Fabrizio Angius |

Image by Fabrizio Angius |

When you fill up your water bottle, take a shower in the morning, or wash the dishes after dinner, how often does the privilege of having clean, fresh water delivered to you on demand cross your mind?  Residing in a well-developed country, the term ‘water scarcity’ often triggers thought of global news headlines, rather than issues we deal with first hand—issues for drought-prone Australia or California to deal with (a regularity in recent years).  Overcrowded developing countries might come to mind where human demand exceeds water availability.

Extreme weather systems hit Canadians a little harder.  Cities all across the country have had their share of rain, hail, and ice storms in recent years.

Can something be done to ease water crises and destructive weather events both globally and at home?  There are solutions!  (Otherwise, I probably would have just ended this here).  Cloud seeding is the phrase of the day; a weather modification technique used to force precipitation by manipulating the timing of when rain and snow droplets will fall from a cloud to Earth.

Is cloud seeding technology scientifically sound and ethical to implement on national scales?  This question is more debatable.  

How to “seed” a cloud.

Glaciogenic seeding is term applied to seeding clouds at high altitude, usually accomplished using silver iodide flares.  The role of silver iodide is to, within a cloud, increase the chances that ice crystals will form at temperatures colder than -50°C.  Specially-equipped planes fly over clouds with high water potential, releasing the aerosol to provide particles for water to freeze to.  Ice crystals fall from the clouds once they get too heavy and these crystals transform to rain or snow as they descend to the ground.

Targeting warmer clouds at lower altitudes is termed hygroscopic seeding. In addition to silver iodide, sodium, lithium or potassium salts may be used to generate larger droplets.  Similarly, these chemicals supply a larger medium to coalesce smaller droplets, promoting precipitation.

No time for science.  Need water now!

Very few rigorous scientific studies are published on the impacts of cloud seeding.  Given the difficulty in tracking influences on the hydrological cycle upon “making it rain” when weather technicians so desire, it is unsurprising that so much scrutiny surrounds the topic.  China is the frontrunner in annual production of rain as a result of cloud seeding.  Despite their intensive use of cloud seeding products, Chinese atmospheric scientist, Zhang Hong-fa, acknowledges that China is “very much behind” in being able to provide sufficient evidence for the success and environmental impact of cloud seeding in the country.

Spending upwards of 60 million USD, China has landed 32,000 employees to operate 35 customized planes and over 12,000 rocket launchers for releasing aerosols to seed clouds.  Their efforts nationwide translate to over 50 billion cubic meters of artificial rain annually. To provide perspective, this quantity of water is 1.5 times the volume contained in the Three Gorges Reservoir, the largest hydropower plant on Earth!  

Part of the technology’s traction has come about through the question surrounding whether cloud seeding will become an integral component of human livelihood.  Programs are broadly implemented despite the lack of concrete environmental assessment, servicing two thirds of the country’s 2,900 counties.  Farmers in China have become so dependent on cloud-seeding operations that transboundary conflicts have initiated.  Neighbouring villages have accused others of “stealing” their water by unnaturally forcing rain onto their district when air masses with high water potential may have otherwise drifted downwind.

While this behaviour emphasizes the need for improved proprietary regulations for cloud seeding, it speaks highly to the demand for the technology.  China, home to roughly one fifth of the global population, has 6% of the Earth’s freshwater resources.  The industrial and power-generating sectors impose even more pressure on the water supply.  Consequently, more than 70% of the freshwater lakes and rivers in the country are polluted.  Given the circumstances, it is practically indisputable to see why cloud seeding has become the norm to help augment China’s pressured water supply.

One of the longest-running and most rigorous tests to date is ongoing in Wyoming, USA for the past several winters.  Cloud seeding has been estimated to increase precipitation by 5-15% in the Medicine Bow mountain range, but bias in these results has also sparked substantial criticism of the practice.  Similar to China, water rights in the Colorado River basin are resentfully disputed between seven US states and Mexico.  Despite mixed results in experimentation, a program is moving forward to increase the winter snowpack on the Wyoming mountain range to alleviate the water stresses cities and farms deal with annually.

Canada’s cloud seeding cause.

An alternate motive has caused cloud seeding to lift off the ground in Canada.  On August 7th 2014, meteorologists at the Alberta Severe Weather Management Society detected five supercells (something like rotating thunderstorms) descending on central Alberta.  The city of Airdrie, 30km north of Calgary, was hardest hit by the baseball-sized hail pellets raining from the sky.  The province of Alberta was left with $25 million in damage costs, but this figure would have been much higher had the 5 supercells of the August 7th hailstorm not been seeded prior to hitting Airdrie and other cities in the region.

The summer of 2014 served as the second busiest and most expensive cloud seeding season in Alberta’s history: 92 hailstorms were targeted on 29 days.  Pilots fly directly into the storms, releasing silver iodide into the clouds to expedite the formation of ice crystals, snow and small hail.  Avoiding large balls of hail is the aim of cloud seeding across the province.  Without this technology to decrease storm intensity, Albertans would be faced with 40% more damage costs from the powerful summer storms.

Although the technology is based on spewing silver iodide directly into the atmosphere, cloud seeding contributes 100 times fewer emissions of silver into the environment compared to common industrial applications.  Although silver can be toxic in high quantities, it has not been detected in concentrations exceeding background levels within cloud-seeded regions of the world.

To seed or not to seed?

If this geoengineering practice grows at an unprecedented rate, silver released by cloud seeding flares may eventually exceed healthy limits, leading to adverse ecosystem and health impacts.  Likewise, I anticipate overproduction of rain and snow may prompt local flooding events due to increased runoff that is beyond the capacity of urban storm water infrastructure. 

Similar to how cloud seeding has modified the weather in countries worldwide, the big question underlying the technology should also be modified.  Cloud seeding is happening, and will continue to receive funding because of its overwhelming benefits for humans threatened by severe weather storms and insufficient water sources.   The ever-increasing demand on water resources screams, “Seed!” if we are to meet the basic human right to life for the seven billion (and counting) humans on the planet.  Access to potable water is strongly engrained in that right.  Cloud seeding is an effective way of reaching that objective.

Although technologies like cloud seeding relieve some strain on critical global emergencies, it is equally important to know that the ultimate long-term success of the technology depends on our ability to sustainably carry out such programs without altering the Earth’s grander elemental cycling schemes.  Climate scientists must be given the resources to evaluate any potential chronic impacts of cloud seeding in order to confirm that we are not running ourselves off a cliff by poking at climate change from another angle.