As world leaders grapple with reducing greenhouse gases, Harvard scientists are planning to send a balloon into the stratosphere that will spray aerosols to test their ability to reflect sunlight as a way to cool the planet. It’s part of a promising field of research called “solar geo-engineering” that aims to fight global warming.

But scientists are coming up against another problem: conspiracy theorists who are convinced that they’re spraying chemicals for the purpose of mind control.

A new report by Harvard researchers published in the journal Nature has found that a whopping 60 percent of online posts about solar geo-engineering are conspiracy theories about chemtrails. And scientists are even receiving death threats from chemtrail believers.

“You’re a part of this mass conspiracy killing life on Earth as we know it”

“You’re a part of this mass conspiracy killing life on Earth as we know it,” one of the report’s authors Gernot Wagner told VICE News, quoting some of the hate mail he has received.

Searching the term “chemtrail” yields photo after photo of white streaks in the sky. These streaks are actually contrails — the condensation left by planes as they zoom through the sky. But chemtrail conspiracy theorists believe the planes are spraying chemicals for weather control, or even mind control.

Alex Jones of InfoWars, who does not believe in human-caused global warming, asserts that chemtrails are part of a government program in which chemicals are secretly added to jet fuel.

“I’ve been talking about this forever,” he exclaimed in a recent video about chemtrails, global warming and geo-engineering. “There is an entire atmospheric terraforming geo-engineering manipulation. They don’t call it chemtrails. And of course the CIA director admitted they have this huge program.”

In another recent video Jones says, “There is manipulation of the weather. It’s mainstream news, and the media always picks it up and says I’m crazy. It’s on the Weather Channel that there are secret programs. It’s just so secret we don’t know the details.”

Chemtrails are not real. They have been widely debunked, Wagner’s paper states, but 2016 survey data shows between 30 and 40 percent of the general U.S. public believes in them.

The Harvard report used an algorithm to analyze a decade of social media posts about solar geo-engineering between 2008 and 2017, mostly on Twitter, to see how many were conspiracy theories and how many were scientific. The majority — 60 percent — were conspiracy theories.

Some of the same people who believe in chemtrails are also tweeting about Alex Jones and InfoWars, Wagner told VICE News. Anonymity online helps spread these ideas, he says.

Wagner says he has received “plenty of emails” accusing him of being a mass murderer. His colleagues have received them, too.

“It is a pretty frustrating situation to be in”

In one of his recent chemtrail videos, Jones said scientists can “kill anybody they want” under “research provisions,” which could explain some of the threats Wagner and his colleagues have faced.

“It is a pretty frustrating situation to be in,” Wagner says.

“This is a relatively new topic,” Wagner says of solar geo-engineering, which has only been researched for 15 years as a way to fight global warming, “There is very little discourse on geo-engineering in general, and now what happens is it’s being dwarfed by, dominated by, those spreading this conspiracy theory.”

What is solar geo-engineering?

As greenhouse gas emissions (GHGs) continue to increase, they are trapping heat from the sun’s rays, warming the earth and contributing to climate change. The vast majority of world leaders and scientists believe the best way to limit global warming is to reduce greenhouse gas emissions by switching to renewable energy sources. Another strategy is to capture carbon from the atmosphere and store it underground.

Scientists see it as a complement to reducing GHGs, or a last resort.

For the past 15 years, scientists have been studying solar geo-engineering in the lab as another possible tool to limit global warming. Scientists see it as a complement to reducing GHGs, or a possible last resort if emissions continue to rise. The research is hypothetical at the moment, and has not yet been tested in the real world, Wagner says.

When they send a balloon to the stratosphere next year as part of a project called ScopeX, Harvard scientists will be taking the technology from the lab into the real world for the first time.

Spraying aerosols to reflect sunlight is a relatively cheap option. Scientists are essentially copying a natural mechanism that has been proven to cool the planet: volcanic eruptions. Volcanoes release sulphur which turns into sulphate aerosol at high altitudes. These aerosols have been shown to reflect sunlight, almost like a sunscreen. But sulphur is also known to deplete ozone, a gas which helps protect the planet by filtering sunlight as part of the ozone layer, which makes the technology risky. Scientists want to experiment with different reflective substances like calcium carbonate (found in limestone) or even diamond dust to find the safest option.

There are known risks.

For instance, a study published last week in the journal Nature used computer models to investigate how sulphur dioxide injections would impact hurricanes in the North Atlantic. The research shows injecting it into only the Northern hemisphere would reduce hurricanes in the North Atlantic. However, if it was injected only in the Southern hemisphere, the sulphur dioxide would increase the number of hurricanes.

The takeaway from this and previous studies was that solar geo-engineering, if used evenly across the planet, could reduce the impact of global warming, and if it isn’t used evenly, it could be risky. However, no one in the solar geo-engineering community is advocating for it to be deployed unevenly, according to Anthony Jones of the University of Exeter in the U.K.

The scientific community is first asking for world leaders to reduce GHG emissions, and if that is not successful, they want solar geo-engineering to be properly researched and regulated so if it is eventually used in the fight against climate change, officials will be able to weigh the potential risks and rewards.