Farmers in Mexico have accused Volkswagen of ruining their crops by installing “hail cannons”, which fire shockwaves into the atmosphere in an effort to prevent hail storms from damaging the cars rolling off the production line.
The devices are being blamed for causing a drought during months when farmers near the German carmaker’s plant in Puebla expected plenty of rain.
While some may be convinced of the hail cannon’s power, scientific research has cast doubt on these observations. But effective or not, the technology represents humanity’s latest attempt to control the weather – rain dancing 2.0 – and has raised concerns about the lack of regulation and the assumption that there is a quick fix for complex meteorological phenomena.
Both hail cannons and hail rockets emit loud noises in the sky, and manufacturers claim this disrupts the formation of hail so that it falls instead as rain or slush.
In 2005, Nissan installed 20ft hail cannons at its plant in Mississippi after a hailstorm, much to its neighbours’ annoyance. When activated, the system fired off gunshot sounds into the sky every six seconds. “It was like having a boombox in my driveway,” said one neighbour at the time.
Farmers have also used hail cannons to try to prevent their crops from being crushed.
However, a review by the Dutch meteorologist Jon Wieringa concluded that these technologies were “a waste of money and effort” – a sentiment echoed by the World Meteorological Organization.
“The only beneficial effect of firing explosive rockets and grenades at hail clouds may be the emotional satisfaction of the gunners, who have fired at the enemy,” he wrote.
Cloud seeding has been shown to be more effective at controlling precipitation. It involves shooting chemicals into clouds – often from a small aircraft – to cause rainfall or snow.
It’s done in more than 50 countries worldwide for various reasons including dispersing fog at airports, reducing property damage from giant hailstones in Canada and to increase snowfall in Colorado and summer rainfall in Texas.
“You have to be very careful about what types of clouds and what you are trying to do,” said William Cotton, a professor of atmospheric science at Colorado State University.
Seeding wintertime mountain clouds can, he said, increase precipitation by 6-8%. “That’s enough for a lot of water users to be happy and willing to pay for it,” Cotton said.
The evidence to support summertime cloud seeding seems to be much more shaky, with the National Research Council concluding in 2003 that “there is still no convincing scientific proof of the efficacy of intentional weather modification efforts”.
Critics are concerned that manipulating the weather is only treating the symptoms of drought rather than tackling the underlying causes.
“Even if it’s local, it’s worrying that in the face of climate change these kinds of alternatives come up,” said Silvia Ribeiro, the Latin America director of ETC Group, which examines the socio-economic and ecological impact of new technologies. “We control the symptoms instead of modifying what is producing the effect.”
That hasn’t stopped states and businesses from continuing to seed clouds, in some cases on a dizzying scale. The Chinese government is developing the world’s most ambitious cloud seeding project to boost rainfall across the Tibetan plateau, an area spanning 620,000 sq miles – three times the size of Spain.
The state-owned China Aerospace Science and Technology Corporation has designed and constructed chambers that use military rocket engine technology that burn fuel to produce the cloud-seeding agent silver iodide. When the chambers are installed on mountain ridges, the particles travel up into the clouds and trigger rainfall in one of the driest places on Earth.
Because of the large area covered, some are concerned that the Tibet project teeters from weather modification into geoengineering territory.
“Weather modification tends to be quite local. You do it, it happens. You stop and it’s gone. Geoengineering, or modification of the climate, means you do something in a way that it stays like that,” explained Janos Pasztor, the executive director of the Carnegie Climate Geoengineering Governance Initiative, which seeks to create effective governance for climate engineering technologies.
“If [weather modification in Tibet] were done long enough, it will have an impact on the climate, not just the weather,” he said.
The main geoengineering approaches include removing carbon from the atmosphere and changing the clouds in the stratosphere so they reflect the sun’s rays back into space.
The latter approach – solar engineering – involves flying aeroplanes into the stratosphere to spread particles such as sulphur, whichthen form tiny particles called aerosols that can reflect light away from Earth. It’s designed to simulate the cooling effects of a volcanic eruption, but “without all the ash and the big bang” said Pasztor.
So far, there have only been a handful of small experiments, but much more research needs to be done if it’s to be deployed as an Earth-cooling technique.
Meddling with the climate in this way is highly controversial and raises all sorts of ethical and logistical questions.
“This would be the most global endeavour humankind has undertaken. Who is going to make the decision to do it? Trump? The head of Exxon? The UN general assembly?” asked Pasztor, who is urging governments to develop policies to prevent a rogue country of billionaires taking matters into their own hands.
“We have one atmosphere so we must get it right,” said Pasztor.
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