Making It Rain

Roman Mars:
This is 99% Invisible. I’m Roman Mars.

Roman Mars:
August 24th, 1814 marked the first and only time Washington D.C. was occupied by outside forces.

Vivian Le:
The United States was two years into the war of 1812. They’d taken on Great Britain, which was then the greatest naval power in the world, and things weren’t looking great for the American troops defending D.C.

Roman Mars:
That’s producer Vivian Le.

Vivian Le:
British forces overtook the city and set fire to historic American landmarks, including the Treasury Building, the Capitol Building, and even the White House. The siege became known as the Burning of Washington.

Roman Mars:
But then, a freak occurrence, which in any other situation would have been a total disaster for D.C., saved the city.

Vivian Le:
Dark clouds began to form, which turned into thunder and lightning, which then turned into a full-blown tornado that headed straight for the British who were setting fires around the Capitol.

Roman Mars:
A number of British soldiers were killed by falling debris and the fires were extinguished by the rain. The British retreated back to their ships, which had been severely damaged by the storm.

Roman Mars:
Thanks to a simple act of weather, the occupation of our nation’s Capitol was over within a little more than a day.

Vivian Le:
The storm that saved Washington was just one of countless times that weather played a crucial factor in war. Napoleon’s army wasn’t defeated by Russian forces, but by a Russian winter. And during World War II, General Patton famously distributed 250,000 prayer cards to the Army to enlist as many men as possible to pray for an end to the rain.

Roman Mars:
The battlefield has always been at the mercy of the climate, but there was a time in U.S. military history when we did more than just pray for advantageous weather. We tried to create it.

Archive Tape:
Fighting communist guerrillas in South Vietnam continues a slow grind. Pictures from the swampy Mekong delta show government troops trying to ferret out the Vietcong. In a situation…

Vivian Le:
Beginning in the 1950s and continuing into the 1960s and ’70s, the U.S. became deeply entangled in a war between North and South Vietnam. North Vietnam was supported by the Soviet Union, China, and other communist allies. South Vietnam was supported by the U.S. and other anti-communist allies.

Roman Mars:
And the Vietnam War, or as the Vietnamese called it, The American War, was unlike any the United States had ever engaged in.

Merrill McPeak:
Our tradition, and our heritage, and our education, and our history all prepared us for a different kind of war than we had to fight in the late ’60s.

Roman Mars:
This is General Merrill McPeak, former Chief-of-Staff of the Air Force.

Merrill McPeak:
There wasn’t a front line. And we weren’t facing an enemy, at least in the beginning, that was equipped with tanks and flame throwers and high-speed computers and so forth. It was a total mismatch from that standpoint. It was us against a guerrilla army that showed up occasionally and then disappeared, vanished. And we’d spent the next months looking for it, and then it showed up suddenly, and then it was gone again.

Vivian Le:
That guerrilla army was the Vietcong, a communist force allied with North Vietnam, but fighting primarily in the South.

Roman Mars:
One of the Vietcong’s greatest advantages was the Ho Chi Minh Trail, a supply route that ran from North Vietnam through parts of Laos and Cambodia into South Vietnam. Hundreds of thousands of North Vietnamese troops used it to infiltrate the South with weapons and supplies.

Vivian Le:
It traveled through an isolated region full of rugged mountains and dense jungles. The trail itself was made up of dirt paths and handmade tunnels. Along the way, there were hidden bunkers, barracks, and even hospitals cleverly camouflaged from above.

Merrill McPeak:
It was an engineering marvel. It wasn’t a single road. It was a network, a maze of roads.

Roman Mars:
The covert trail system dramatically shorten the journey from North to South Vietnam, meaning more troops, more weapons, and more North Vietnamese support could be made available to communist forces in the South.

Ed Soyster:
And the key thing was, that’s how all their supplies, as they supplied both the Vietcong and also their own forces, had to come down that trail.

Vivian Le:
This is Lieutenant General Ed Soyster.

Ed Soyster:
And in order to cut off the supplies, which are of course very important for a military operation, we had to close this trail by various means.

Vivian Le:
The U.S. military tried disrupting the trail with bombing campaigns and by plowing the jungles to strip the land. They also use deadly chemical defoliants like Agent Orange, but none of these tactics seem to work. At least, not for very long.

Merrill McPeak:
So whenever we punched a hole in one part of it, they simply moved over to a bypass.

Roman Mars:
There was only one thing that significantly slowed the flow of supplies and people on the Ho Chi Minh Trail – rain.

Ed Soyster:
The reality was that, because of the nature of the trail, it was affected by heavy rainfall. So they had the same problem, of course, as we did in terms of trails that were very, very muddy with the rain.

Vivian Le:
The mud would make the trails difficult to navigate. And so, during one monsoon season, in the middle of the war …

Ed Soyster:
Somebody, certainly not me, came up with the idea of, “Let’s see if we can increase the rainfall enough to stop vehicular traffic.”

Roman Mars:
The Department of Defense had decided that they should try to control the weather.

Vivian Le:
This was the beginning of a top-secret military project called Operation Popeye. The goal was to actually create more rain in Southeast Asia by artificially extending and intensifying the naturally-occurring monsoon season.

Roman Mars:
The monsoon season typically lasted from April to October. The U.S. military believed that if it could extend it by a month on either side it would create a huge strategic advantage.

Roman Mars:
Humans, especially military humans, have wanted to control the weather for a long time.

Jim Fleming:
It goes back to traditional rainmaking, to ceremonies.

Roman Mars:
This is Jim Fleming. He’s studied the history of human attempts at weather and climate modification. He doesn’t think very highly of our abilities.

Jim Fleming:
It turns out that if you do a rain dance for up to two weeks, it’ll probably rain, and then you could take credit for that. I mean, if you do anything long enough and consistently enough, it’ll rain, and you can claim responsibility.

Vivian Le:
Fleming says that in the 19th century, after the Civil War, a theory began to develop that major military operations were somehow disrupting the clouds and causing big rainstorms.

Jim Fleming:
And so, the theory was that we could shoot cannon fireworks, set off hydrogen balloons. We could sort of imitate battle.

Roman Mars:
Imitate battle in order to create rain. The federal government actually attempted this in Texas in the 1890s during a drought.

Jim Fleming:
The actual Department of Agriculture funded it, and they had a Weather Bureau observer there, and the locals loved it. They loved the fireworks. They loved the spectacle. They loved to go out on the hillside and watch the cannonading, but it was during the monsoon season, and so, there was a really good chance it was gonna rain anyway.

Vivian Le:
This kind of experimentation continued from the 1890s into the early 20th century, and it only accelerated after 1945. We’d entered the Cold War era, and we’d just invented the bomb.

Jim Fleming:
And that technology made people think they had power over nature.

Roman Mars:
It also heightened our paranoia that other countries were trying to develop their own nature controlling technologies, like the Russians.

Roman Mars:
Before the Space Race with the Soviet Union, there was a kind of Weather Race.

Jim Fleming:
We thought that they might get ahead of us, and if they had a nefarious purpose, they might be able to change our weather and climate, and possibly cause another Dust Bowl or drought or something if they really could do it. So there was a great rush to get into this field. Again, it was driven by military concerns.

Vivian Le:
There was a lot of money being poured into scientific research on weather control, and while many of these experiments didn’t yield very promising results, one actually did, in 1946

Archive Tape:
For the first time in all history, there is now open to man the possibility of exerting some control over the weather. Probably the most remarkable achievement of the year.

Roman Mars:
This remarkable achievement happened in Schenectady, New York at the offices of General Electric.

Vivian Le:
Yep. The same company that made your dishwasher also invented weather control.

Roman Mars:
GE was where a scientist and Nobel Laureate, named Irving Langmuir, was working in collaboration with a colleague named Vincent Schaefer…

Jim Fleming:
Who developed a technique of dry ice put into a cloud that would make it super cool and force the conditions to go way below freezing, and a little bit of ice in the cloud could cause a cloud to glaciate or create snow.

Roman Mars:
In case you didn’t quite get that, here’s a quick lesson in eighth-grade cloud physics.

Vivian Le:
Clouds are essentially just tiny droplets of water suspended in the atmosphere. When the right conditions occur, water molecules in these clouds will condense together and become heavy enough to fall to earth as rain or snow.

Roman Mars:
And that’s what Schaefer had to figure out how to do. He figured out how to create the conditions in the cloud such that it would produce rain or snow.

Vivian Le:
In parallel with that breakthrough, there was another guy doing instrumental work at GE. His name was Bernard, or Bernie, Vonnegut, the brother of author Kurt Vonnegut, who also worked at GE in the PR department.

Roman Mars:
And it’s interesting, you can actually see the ways that GE influenced some of Vonnegut’s writing.

Jim Fleming:
Kurt was on staff at GE writing his reports, but he was also working on novels, you know, like Cat’s Cradle in which the mad scientist, kind of like an Irving Langmuir-person, develops Ice-Nine, which messes up the environment.

Roman Mars:
Ice-Nine was kind of like cloud seeding on steroids. It’s clear that Bernie and Kurt, these two brothers, were uneasy about some of the breakthroughs they were involved with.

Jim Fleming:
And I think you’ll see some of Bernie’s concerns reflected in Kurt Vonnegut’s novels, which are pretty much against militarization of nature,

Vivian Le:
But Bernie’s work at GE actually helped lay the groundwork for that militarization. Along with Langmuir and Schaefer, he made another critical discovery. He found a new weather-related use for a compound called, “silver iodide.” It had a hexagonal structure, like a snowflake, and he found that if you sprayed it into a cloud, it would trick the cloud into glaciating.

Jim Fleming:
And so, armed with a Nobel prize winner, a technique to super cool a cloud with dry ice, and a technique to trick a cloud with silver iodide, they really felt they had the basis for chemical cloud seeding.

Roman Mars:
GE was, understandably, very proud of their discovery.

Jim Fleming:
And so, they issued a great big press release that said, “We can control the weather!”

Vivian Le:
But shortly after claiming responsibility for a storm that caused eight inches of snowfall in upstate New York, GE suddenly realized that they might not want to be known for controlling the weather, especially if that weather was destroying people’s property.

Jim Fleming:
Within several months, their lawyer says, “No, we better keep that quiet because there could be too many lawsuits.”

Roman Mars:
Given the risk of negative public reaction and liability, weather modification research continued, quietly. Scientists explored how it could be applied to hurricane intervention and drought relief. And, of course, warfare.

Roman Mars:
Langmuir himself was excited about the military applications of his research.

Jim Fleming:
And I think he wanted to have kind of a gigantic role by using weather as a militarized weapon. A hurricane is multiple H-bombs, and incredible destructive power if you could direct it against an enemy. So, Langmuir was making these kinds of claims.

Vivian Le:
And so were our political leaders. With nuclear weapons now in play, the U.S. was looking forward and imagining how we could give ourselves an edge in future wars. This is from a speech that Vice President Lyndon Johnson gave in 1962:

LBJ:
It lays the predicate and the foundation for the development of a weather satellite that will permit man to determine the world’s cloud layer, and ultimately, to control the weather. And he who controls the weather will control the world.

Roman Mars:
LBJ or Bond villain? You decide.

Roman Mars:
By the time rainmaking had made its way to the Ho Chi Minh Trail in Southeast Asia, it wasn’t a new technology, but it was still a closely held secret.

Vivian Le:
Operation Popeye was a Navy program, and missions were flown by Air Force pilots, and those pilots were given limited information about what they were doing.

Brian Heckman:
I never even imagined that that’s what that group was doing until we got over there and showed up for the briefing. And then, they told us what this project is about.

Vivian Le:
This is Brian Heckman, a former Air Force pilot. He belonged to the 54th Weather Reconnaissance Squadron. They contributed to the 2,602 cloud seeding missions flown during Operation Popeye.

Brian Heckman:
We just went around looking for clouds to seed.

Vivian Le:
Once they found a cloud to fly through, they’d flip a switch to ignite silver or lead iodide flares, then they’d wait to see if the cloud produced rainfall.

Brian Heckman:
There were times when we left an area that we had been working, and it was obvious that there was a lot of rainstorms going on.

Roman Mars:
Operation Popeye had four main objectives: To turn the roads to mud, to cause landslides along roadways, to wash out river crossings, and to keep roads muddier for longer than usual.

Vivian Le:
It seemed to Heckman that Operation Popeye was working, but it’s really hard to know for sure.

Roman Mars:
Cloud seeding at the time, and even today, is far from an exact science. At best, the military could measure three things: what the average rainfall for that area was, what the estimated rainfall would have been, and what actually fell after a seeding mission.

Vivian Le:
But they couldn’t collect that much data, like enough to really rigorously analyze the outcomes. Here’s Fleming again.

Jim Fleming:
The rain is completely a variable. You have tremendous temporal variability, spatial variability, and that means the statistics are not robust about what your particular intervention did to that particular rainfall.

Vivian Le:
And even if they could make it rain, they couldn’t precisely control where that rain landed. One official described accidentally dumping a ton of rain on an American Special Forces camp.

Roman Mars:
Still, the program was deemed effective enough to continue for five years, from 1967 to 1972.

Vivian Le:
But the biggest problem with Operation Popeye wasn’t so much the lack of quantifiable success, it was the many ethical concerns. Weather modification, especially in the context of war, raises a lot of thorny questions.

Roman Mars:
The military justified the program by arguing that increasing rainfall to create mud and wash out roads was preferable to more bombing.

Vivian Le:
But the reality is, the U.S. military still dropped a lot of bombs on Southeast Asia during the Vietnam war. Over 7 million tons of them. So many, in fact, that to this day, the government of Laos is still trying to clean up all of the un-detonated bombs scattered across the country. Here’s General Merrill McPeak again.

Merrill McPeak:
We dropped more bombs on Laos than we did on Germany and Japan all together in World War II. So, the tonnage of bombs dropped was enormous. And the heavily used parts of the Ho Chi Minh Trail looked like the face of the moon. I mean, it was just a lunar landscape, nothing but dust.

Roman Mars:
But just as it’s unclear how much rain was generated by Operation Popeye, it’s also unclear if Popeye actually prevented the military from dropping more bombs, or if they just did both.

Vivian Le:
And messing with another country’s weather system, that has potentially big and unpredictable consequences.

Jacob Hamblin:
You don’t necessarily know what the longterm consequences are going to be of rainmaking…

Vivian Le:
This is Jacob Hamblin, a historian at Oregon State University.

Jacob Hamblin:
… especially if you’re doing it on a long-term basis.

Roman Mars:
And there are documented cases in which weather modification may have caused harm. The silver iodide sprayed into clouds can be toxic to humans in concentrated doses, but it hasn’t been shown to have negative health effects when used for cloud seeding.

Roman Mars:
Nevertheless, cloud seeding may have caused other problems. In 1947, Irving Langmuir’s research team at GE tried to break up a hurricane by dumping a lot of dry ice into it to see if it would collapse, but instead, it changed trajectory, became stronger, and hit the Georgia coast. One death was reported as a result of the hurricane.

Vivian Le:
And in 1952, the British Royal Air Force was conducting cloud seeding tests in Lynmouth, England and may have accidentally caused a devastating flood that killed 35 people.

Roman Mars:
It was this kind of ethical ambiguity that ultimately ended the U.S. military’s entire weather weaponization program. In 1971, Jack Anderson, the reporter for the Washington Post, published an article revealing that the U.S. was engaged in covert weather warfare in Vietnam. This report was corroborated by information leaked in the Pentagon papers.

Vivian Le:
The following year, in July of 1972, Seymour Hersh reported in the New York Times about Operation Popeye. Within two days of the story’s publication, the entire program was officially ended and all cloud seeding missions stopped.

Roman Mars:
When the program was finally declassified and it came out that the U.S. had been secretly engaging in hostile weather manipulation in Vietnam, it was dubbed “the Watergate of weather warfare”.

Roman Mars:
But they really should have called it “Weathergate”.

Jim Fleming:
This led to a kind of an embarrassing – tremendously embarrassing – moment for the U.S.

Roman Mars:
Here’s Jim Fleming again.

Jim Fleming:
It’s perceived as a big mistake. It’s just an embarrassment, that you would try to intervene in a nation’s weather like that.

Vivian Le:
Research money for weather control rapidly disappeared.

Roman Mars:
And in 1977, the U.S. signed an international agreement called the Environmental Modification Convention Treaty, or ENMOD for short, along with the Soviet Union and many other nations. They agreed to ban modification of the environment for hostile purposes.

Vivian Le:
The treaty outlawed causing earthquakes and tsunamis, steering hurricanes, or tampering with the ionosphere. It also banned any other widespread, long-lasting, and severe damage to the environment. But there are questions about whether the ENMOD Treaty was even that relevant.

Jacob Hamblin:
It’s was easy to ban environmental warfare. And the reason it was easy to ban is because you’re not giving up anything, because those things no longer were considered to be important parts of the arsenal.

Jacob Hamblin:
They were developed during your time when the U.S. wanted to develop lots of different weapons systems, but by the time you get to the 1960s if there was going to be a war with the Soviet Union, it was going to be a nuclear war. It was going to be a war in which thermonuclear weapons were used. Intercontinental ballistic missiles were probably going to be used.

Roman Mars:
And so, Hamblin believes that giving up environmental warfare was more a gesture of global cooperation rather than an actual step towards disarmament. After all, it’s hard to find something that can cause more widespread, long-lasting, or severe damage to the environment than nuclear weapons.

Jacob Hamblin:
Those certainly were not banned. So, the ENMOD Treaty, you could argue, yes, sure it’s progress, but I would encourage us all to take a more cynical view of that and see that it was signed for very political purposes and really gave virtually nothing up.

Roman Mars:
The military interest in weather control had run its course, but cloud seeding is something that still takes place all over the world for another reason, money. A major percentage of the economy is weather-sensitive, from agriculture to energy, to insurance, to the travel industry.

Vivian Le:
More than 50 countries openly have some form of weather modification program. China attempted to use cloud seeding to clear skies over the Beijing Olympics. There’s even a company in the U.K. that offers a wedding package that includes cloud seeding, which can be used to burst rain clouds and make them disappear. The company claims they can guarantee a rain-free wedding day.

Roman Mars:
And that will only set you back about $150,000.

Vivian Le:
As the conversation shifts away from the Cold War to the present-day threat of climate change, people are starting to talk about the use of geoengineering to fix the problem.

Roman Mars:
Suggestions have been thrown around like brightening the clouds to reflect radiation back into space or spraying reflective particles into the stratosphere to cool down the planet. People have proposed giant space umbrellas. We’re even trying to change the orbit of the earth so that it’s slightly farther from the sun.

Vivian Le:
Changing the weather is one thing, but changing the climate on a permanent scale is next-level meddling.

Roman Mars:
Many people are highly doubtful that geoengineering can be used effectively to stop the warming of our planet. Anything we try would be extremely experimental with unknown consequences.

Jacob Hamblin:
That’s the main issue. Do we have a right to mess around? Do we have a right to tinker with things and allow things just to happen? Whether it’s the free market or some geoengineer who wants to try some new trick, do we have the right to do that when we know it’s going to have global consequences?

Roman Mars:
Weather systems are so complex that it’s pretty much hubris to think we can intervene in predictable ways, but as long as the stakes are high, whether it’s a war, or you know, the fate of the planet, people will probably keep trying.