Viral posts blaming “weather-control planes” for July’s deadly floods in Texas — and, by extension, last year’s Hurricane Helene in North Carolina — are ricocheting across social media and even Capitol Hill. But atmospheric scientists say the physics simply don’t add up.
“You might squeeze out a few hundredths of an inch of extra rain, enough to help a farmer, nowhere near enough to flood a county,” said Dr. Gary Lackmann, professor and head of atmospheric sciences at N.C. State University.
What cloud seeding can (and can’t) do
Cloud seeding, developed in the 1940s, involves releasing silver-iodide or dry-ice particles into cold clouds to jump-start precipitation. The technique is used primarily in the drought-stricken West, and any boost in rainfall is measured in sub-centimeter amounts, according to Rainmaker, a Texas firm that performs the service.
Rainmaker’s aircraft did fly a 20-minute seeding mission two days before last week’s Texas deluge, but company CEO Augustus Doricko said the target area was “well outside the flood zone,” and the effect of any seeding typically fades within an hour.
“We’re talking about, like, sub centimeter amounts of precipitation, be it in snow or rain from every event, which in aggregate is very consequential for farmers and ecosystems, but cannot come close to causing flooding unto itself,” Doricko said.
Lackmann concurs. “You can influence a local shower,” he said, “but you can’t manufacture a stalled tropical plume that dumps a foot of rain.”
The real fuel: record-warm seas
What did super-charge both storms, Lackmann says, was water vapor pulled from unusually warm oceans.
“Parts of the Atlantic off North Carolina are running four degrees Celsius above average,” he said. “Warmer water means more moisture and more fuel for extreme downpours.”
For every degree Celsius of warming, the atmosphere can hold roughly 4-7% more water vapor, a relationship scientists have understood since the 1820s.
A push for a statewide ban
Still, the optics of planes in the sky and flooded streets on the ground have raised political alarms. Rep. Jonathan Almond (R-Cabarrus) introduced House Bill 362, which would prohibit cloud seeding, stratospheric aerosol injection and other forms of geoengineering in North Carolina.
“We need to put a pause on any program until we understand why ‘hundred-year’ storms are hitting so often,” Almond said.
“We really don’t know the full repercussions of weather modification,” he added. “It’s time to set guardrails to protect North Carolinians.”
At least 30 states have considered similar measures, and Tennessee enacted a ban earlier this year.
No current NC projects
A review of federal Weather Modification Project Reports, NOAA databases and state permits shows no commercial or government cloud-seeding operations in North Carolina, past or present. The only documented activity was a feasibility study for hydropower interests in the Yadkin River basin; the project never launched.
Lackmann worries the legislative focus misses the bigger culprit: greenhouse-gas warming.
“Burning fossil fuels is the largest unintentional geoengineering experiment on Earth,” he said. “That experiment is absolutely linked to the spike in extreme rain.”
EPA weighs in
Adding to the debate, EPA Administrator Lee Zeldin on Thursday directed the public to new agency web pages on contrails and geoengineering, writing that Americans “deserve straight answers.” The site states plainly that the U.S. government is not conducting outdoor solar-radiation or stratospheric aerosol projects.
What’s next
HB 362 has yet to receive a committee hearing, but Almond hopes the national spotlight will speed action. Critics counter that the bill chases a problem that doesn’t exist and risks stifling legitimate research into drought relief.