As an extreme drought grips Mexico, leading to crop losses, a lack of water and higher food prices, the government is trying to bring desperately-needed rain by turning to a controversial technology: cloud seeding.
In July, the country kicked off the latest phase of a cloud seeding project that aims to artificially stimulate rainfall. It is targeting 62 municipalities clustered in its north and northeast, with the aim of “combating the effects of drought and contributing to the recharge of aquifers,” according to a statement from the Ministry of Agriculture.
Cloud seeding is a technology first discovered in the 1940s. Since then, it has been used in around 50 countries, including in the United States and China. Mexico has been experimenting with weather modification for more than seven decades.
However, some scientists remain very cautious about the effectiveness of cloud seeding and warn that it is not a solution to drought.
“It has a controversial history because it’s very difficult to prove what you are doing from a scientific perspective,” Roelef Bruintjes, a weather modification scientist at the National Center for Atmospheric Research in the US, told CNN.
For cloud seeding to work, you first need a cloud. Planes or drones inject particles into the cloud that attract water droplets to form around them, increasing the chance of rainfall or snowfall.
“The whole idea is not ‘creating clouds’ – because we cannot make a cloud, we cannot chase away a cloud,” Bruintjes said. “But it’s trying to get a larger percentage of the water that is processed in the cloud down to the surface.”
Mexico’s project involves spraying silver iodide particles into clouds from planes. The government hopes stimulating rainfall can help farmers better cope with the drought that has swept large swaths of the country.
In mid-July, more than 40% of Mexico was in moderate to extreme drought, according to the national weather service. The country has also been sweltering through a severe heat wave that has killed at least 249 people over the past four months.
This extreme weather is only set to get worse – scientists are clear that heat waves and drought will become more common and more intense as the climate crisis accelerates.
Mexico contends that its current cloud seeding project, which it has been running since December 2020, has had a positive impact. In 2021, the cloud seeding flights had created 40% more rain, the government reported – a figure it calculated by measuring the difference between meteorological forecasts and actual rainfall measured by rain gauges.
“Our projects have all been successful,” said a spokesman for the company Startup Renaissance, a rain stimulation company which has worked on the Mexican government project since 2020.
But many scientists remain skeptical.
There is a lack of “hard evidence” that cloud seeding increases precipitation, Fernando García García and Guillermo Montero Martínez of the cloud physics group at the National Autonomous University of Mexico wrote recently.
Bruintjes echoed this. “In most situations you can say, OK, there is rain,” he said. “But is the rain from cloud seeding or is it not from cloud seeding? And that is really the big question.”
The technology is also “not a drought-busting tool,” Bruintjes added, because during a drought, there is often an absence of clouds. “And that’s the one thing we cannot do. We cannot make a cloud.”
Mexico’s Ministry of Agriculture and Rural Development did not respond to a request for comment.
A spokesperson for Startup Renaissance said that criticisms of cloud seeding are based on old technology. The company’s technology is more effective, the spokesperson added, because it sprays the silver iodide, rather the more usual technique of applying it using flares.
Bruintjes does believe cloud seeding could hold promise. There is evidence that US projects aimed at enhancing snowpack over the mountains in states including Wyoming and Idaho have seen some success, he said. But there is a need for much more research and data, he added.
Some experts have called for more attention to be placed on less expensive and high-tech ways of protecting water resources.
Cloud seeding “should be considered only as one element” in a much broader strategy, wrote García and Martínez.