The Montreal Protocol was an international agreement designed to stop the destruction of the ozone layer, and it worked. So why did this one succeed when so many other climate agreements failed? Today we take a look at the ozone situation, the science of why it’s an issue, and how the Montreal Protocol is working to reverse the damage.


In 1987, the nations of the world gathered in Montreal, Quebec, to sign an international environmental agreement that came to be known as the Montreal Protocol.In 1987, the nations of the world gathered in Montreal, Quebec, to sign an international environmental agreement that came to be known as the Montreal Protocol.
On January 1st 1989, the treaty went into effect and to date, 198 UN members follow its provisions as international law.
The problem this set out to fix, as many of you know, is the hole in the ozone layer. And while the ozone hole isn’t… completely fixed, it is well on its way.

Unlike climate change where every report shows things going in the wrong direction, this one is actually getting better, and it’s on track to be completely healed. We actually got this one right.

I know right? Good news, it feels so… Weird…
Many people consider The Montreal Protocol to be one of the most successful international agreements of all time. But why? Why did this one succeed where so many other climate agreements didn’t? And what can we learn from it?

Killer Refrigerators

So you’ve probably heard about the ozone hole and know it has something to do with hairspray or something? But maybe you don’t know exactly what caused it or why.
So let’s start there and talk about what caused the problem in the first place, and that’s CFC’s.

Christian Fundamentalist Churches?
Cold Fructose Containers?
Cosmic Fractal Contaminants?
Canadian Fried Cactus?
Catastrophic Foot Cancer?
California Fart Controllers?

It’s ChloroFluoroCarbons!

ChloroFluoroCarbons,  what’s that?

Well, let me tell you.
Like a lot of things that we create as humans, CFCs were a great thing that became kind-of a terrible thing.
In the 1920s and 30s, refrigerators started gaining widespread use and they were a bit of a godsend. Before refrigerators, people used insulated iceboxes to preserve food, and they had to have ice delivered to their house, there was an entire industry around it.
It’s actually pretty fascinating, it’s one of those industries that completely went away because of technology. But yeah, once the fridge was invented, all you had to do was plug it in and you’re good to go. So they were super popular, everybody loved them… Except, of course, the people at the ice companies.
These newfangled refrigerators did have one downside, though, and that’s the fact that they used methyl chloride as a refrigerant. And the problem with methyl chloride is that is will kinda sorta a little bit but 100% totally kill you.

So if your refrigerator sprung a leak… You died!
Morbid humor aside, this did happen a lot and dozens of people were killed by their refrigerators. One infamous case was the 1929 death of the entire Painter family in Chicago.

Enter Thomas Midgley, Jr., of General Motors, who first invented a way to use CFCs as a refrigerant.

I should note that he didn’t invent CFCs, they had been around a while, but he did figure out how to cheaply produce it at scale and found new applications for it.

Thomas Midgley Jr.

By the way, Midgley is responsible for another environmental catastrophe, he’s the guy who created leaded gasoline.
He discovered that adding tetraethyllead, or TEL, to gasoline would reduce engine knocking. The problem was the lead part.
Lead is highly toxic and can cause a host of health problems including memory loss and lower IQ. 

But that was put in gasoline and people breathed in those emissions for 50 years.
Finally researchers were able to link low test scores to high concentration of lead in the blood of schoolchildren and it finally got phased out.
Some have pointed out that the crime rate in the United States actually went down after they phased out leaded gasoline. That may be more correlation than causation but still.
It’s been said that no single human being has done more harm to the environment than Thomas Midgley, Jr.

Uses of CFCs

Back to CFCs, they solved the refrigerator-killing-people problem but they seemed to solve a lot of other problems as well.They started added it to air conditioning units and fire extinguishers – since it was non-toxic, it became the go-to propellant in practically every household product that used compressed air

Hairspray is the classic example, but they were also used to blow bubbles in styrofoam, as foaming agent in insulation and were even used in medical inhalers.

CFC Dangers

So for a while there, life was pretty sweet for CFC manufacturers, until an article was published in the Journal Nature in 1974.
It was written by Mario Molina and Frank Sherwood Rowland, who went by “Sherry” Rowland.
Sherry, by the way, had an amazing pedigree, he was the student of no less than five Nobel Laureates at the University of Chicago including Walter Libby, who invented carbon-14 dating and Enrico Fermi.

He and Molina had been running tests on CFCs for a couple of years and came to some disturbing findings.
Basically CFC molecules react with light and release a chlorine atom. To explain why that’s a big deal… Here comes the chemistry.

Ozone-Chlorine Chemistry

Okay, so this is ozone, O3, three oxygen atoms bonded together.
When ozone and chlorine mix, it creates a reaction that strips an oxygen atom from the ozone, forming hypochlorite and oxygen, O2.
But in the atmosphere, hypochlorite doesn’t stick around for long, it’s a weak bond and breaks apart pretty easily, which frees that chlorine up to bust up another ozone molecule. And this happens over and over and over.

So a single chlorine atom can smash its way through a bunch of ozone molecules. And by that I mean like 100,000.
Yeah, you know those videos of giant Asian hornets just running through a whole hive of honeybees? That’s basically chorine with ozone.

What’s Ozone Good For?

So in their article, Rowland and Molina warned that this chain reaction could deplete the ozone layer… so let’s talk about the ozone layer for a second.

The ozone layer wraps around the entire planet. It starts low in the stratosphere and reaches high above it, but peak concentrations are between 30 and 35 km.

And the concentration of this layer varies naturally over time. It’s actually part of a cycle of reactions between oxygen and sunlight.

This is called the Chapman cycle, and the way it works is light in the upper atmosphere knocks electrons off oxygen atoms.
This creates a positively charged ion that then sticks to an O2 molecule, creating ozone, O3.
And if another oxygen ion comes collides into that O3, it can break it apart into two O2 molecules, which can then get split apart by light, and the process repeats itself. And this has been going on for millions of years.

The reason this matters is because the wavelength of “light” I keep referring to that’s being absorbed by these oxygen atoms and fueling this cycle is mostly ultraviolet light.
This is how the ozone layer absorbs UV light.

And yeah, UV light is bad. Not only can it lead to cataracts and skin cancer in humans an animals, excess UV can impair photosynthesis in plants and kill bacteria.
In fact, according to NASA, if not for atmospheric ozone, unchecked UV would “sterilize the Earth’s surface”. That would be bad.

So yeah, a massive injection of chlorine hornets chewing through the ozone layer is a big deal.
Now it should be pointed out, chlorine is a naturally occurring element. It’s created by tropical vegetation, forest fires, and some oceanic processes.
But chlorine molecules usually break down before they reach the stratosphere. CFC molecules don’t.
They’re very stable, so the CFC molecules are basically just murder hornet delivery system, driving the chlorine up into the stratosphere where the light hits the CFC, releases the chlorine, and all hell breaks loose.

Discovering the Hole

So, Rowland and Molina’s paper came out in 74, it would be a decade later before scientists at the British Antarctic Survey discovered the ozone hole.
It was actually a physicist named Jonathan Shanklin who made the find, he actually had to dig through some archives to find historic data for comparison but yeah, he found that the ozone over the Antarctic had thinned out by a third.

Now, concentrations change naturally, as I mentioned, but the decline had been steady for several years, and while it is a worldwide problem, it is thinnest over the South Pole.
And there are a lot of reasons for this, too much to go into right now – I’ll put some links in the description but it basically has to do with wind currents and temperature creating unique conditions for stratospheric clouds over  Antarctica, it makes the CFCs a lot more volatile there. But anyway, the hole had been found. Shanklin authored a paper about it that was published in the journal Nature.

Aaaaaand panic set in.

Before Montreal

Because this wasn’t just an isolated report, people had been concerned about ozone depletion for a while.
There was the paper from Rowland and Molina, other people were studying it, and this is kind of interesting, people were worried about Concorde Jets.
Yeah, they actually flew into the stratosphere, and like all jets, they produced a lot of emissions, but the fact that these emissions were going directly into the ozone layer had some people concerned.

It wasn’t really a factor though because there were so few Concordes.
But there had been calls for regulation of CFCs by scientists, including Sherry Rowland, but they were opposed by CFC producers like DuPont Probably because they were making tons of money on it? But we’ll never know for sure.
So regulation was stymied for years but like a teenage boy’s pants, everything changed once they saw the hole.

Right after Shanklin’s paper hit shelves in May 1985, NASA was able to image the hole using satellite data, and within 18 months, UN members had met, authored, and signed the Montreal Protocol.

Now I should point out that there was a previous convention on the ozone issue in March of 85, this one was called the Vienna Convention.
But this one didn’t have any teeth, it was just a treaty about countries sharing knowledge with each other, and was irrelevant literally two months later when the proof came out. So, they had all the knowledge they needed.

Montreal Protocol Provisions

Unlike the Vienna Convention, the protocol required signatories to restrict CFCs.
They were able to do so gradually, in fact, it allowed a period where CFC production and consumption was actually allowed to increase.

Because it had become so ubiquitous in so many things that were already on the market, they had to allow for that momentum to wane. And for replacements to be found.
And originally that replacement was hydrochlorofluorocarbons, or HCFCs, which are obviously chemically similar to CFCs but they decay quickly, so don’t reach the stratosphere. But… they are extremely potent greenhouse gases. Because we can’t have anything nice.
For that reason, they too were later outlawed in an amendment to the Montreal Protocol. Developed nations phased them out by 2020, developing nations have until 2030.
Another alternative was hydrofluorocarbons, or HFCs, and yes, you’re going to hear a lot of acronyms with the same 3 letters over and over.
These were also phased out with an amendment for the same reason as HCFCs; they’re greenhouse gases.

Green Alternatives

And the replacing of CFCs with truly green alternatives is an ongoing process. Many refrigerators and air conditioners still use HFCs, but natural gas refrigerants are becoming more popular.
The particular natural gas is isobutane – it doesn’t deplete ozone and has a low potential for global warming. It goes by R-600a in refrigerators.
It’s Generally Recognized As Safe by the FDA, so is used as a propellant in many cosmetic products. But it is natural gas and subject to the whims of the energy markets.

Another synthetic alternative is called hydrofluoroolefins, or HFOs.
Studies say HFOs should be safe for the environment. The gasses break down quickly, and have low potential for global warming.
Though production of it does release a significant amounts of CO2. That could be said about pretty much everything these days though.

There are also concerns about an acid that forms when HFOs decompose in the atmosphere.
Some studies say these acids are harmless. Others point out we don’t really know what effect a high concentration will have.

After all, unintended consequences are kinda what got us here in the first place.
But I don’t think there’s any reason to worry, the company that produces HFO is called Chemours, which is a division of DuPont, and they were such heroes in the ozone fight that their CEO was given the National Medal of Technology by George W. Bush in 2003.

They actually formed their own lobbying group denying the science for years after the Montreal protocol before finally turning on their heels when the bans went into effect and positioned themselves as the main supplier of CFC alternatives and made massive profits from the crisis…

Ozone Layer Recovery

Between 1979 and 1987, the ozone hole grew from 1.1 million square kilometers in area to 22.5 million square kilometers. And it’s fluctuated since, but has generally declined.
The World Meteorological Organization predicts a full recovery of pre-CFC ozone levels by the end of this century.

And that’s in Antarctica!

People forget that ozone levels are down worldwide, it’s not just that hole at the bottom of the planet. But the good news is the rest of the world is recovering even faster.
They predict the northern hemisphere should recover by the 2030s, and the southern hemisphere in the 2050s.

Protocol Amendments

But this isn’t all just from the original Montreal Protocol, there have been a number of amendments over the years.


The London Amendment in 1990 The Copenhagen Amendment in 1992

The Vienna Accord in 1995 The Montreal Amendment in 1997
The Beijing Amendment in 1999 And most recently, the Kigali Amendment in 2016, which cut HFC consumption by 80%.

If Kigali were an amendment to any other climate agreement, I’d probably roll my eyes. But given the Montreal Protocol’s record, I’m optimistic.
Which begs the question:  Why has the Montreal Protocol been so successful when so many other climate agreements have failed?

The two biggest climate change agreements were the Kyoto Protocol and the Paris Agreement.
Both of these were UN-sponsored attempts at uniting the world against climate change.
Kyoto has been called a fiasco. The world’s biggest polluters, including the U. S. and China, refused to even participate, and several countries that did participate failed to meet their CO2 reduction goals.

The Paris Agreement is kind of a work-in-progress, but none of its targets are legally binding, so it’s kind of hard to imagine it will do any better than Kyoto.
Oh, it should be mentioned, many of the ozone-threatening chemicals banned by the Montreal Protocol over the years also happen to be powerful greenhouse gasses, so some have made the argument it’s actually had a greater direct impact on climate change than Paris and Kyoto.

A key difference between these climate agreements and the Montreal Protocol is buy-in.
Like the US and other developed nations had the most to lose from banning CFCs, but they backed the Montreal Protocol to the hilt.
Granted, this was after years of debating the science, but science was warning about climate change decades before the world knew what CFCs were doing.
So why have we moved so slowly on climate change when we moved so quickly on the ozone layer?
Part of the reason may be the imminent nature of the ozone threat. Remember, the ozone hole grew by a factor of twenty in only eight years.

That makes it pretty easy to get the message across. Not to mention it’s a friggin hole, you can see it, it’s getting bigger.
And it’s a very immediate threat, it’s not some vague threat of sea level rise someday, it’s not a statistical thing over time, it’s if we don’t fix this, I can’t go outside.
Also the substances that need to be controlled for climate change are far more embedded into our economies than the refrigerants that are damaging the ozone layer.
So, it’s a different problem, and it’s far more complicated.

Lessons for Us

But, what can we learn from the Montreal Protocol?
One is that any climate agreement that doesn’t have any teeth is really more of a climate suggestion.
The Montreal Protocol did a great job of threading the needle between respecting each nation’s sovereignty while holding them accountable for meeting their goals.
While other climate agreements like Paris and Kyoto have been criticized for not pushing hard on the accountability side.
The other lesson is that it’s just as important to have a good alternative to the bad thing you’re banning as it is to ban the bad thing.

DuPont made billions of dollars making alternatives to fix the problem they helped cause in the first place. Kinda gross, but it worked.
Perhaps with more incentives, fossil fuel companies could conjure up greener fuel alternatives. Maybe give them a medal!
For the record I’m not saying I like this idea but if it works it works.
But maybe the biggest takeaway from the Montreal Protocol is that yes – this can be done.
We are capable of working together globally to tackle big existential problems. It’s been done. And we can do it again.
And with that comes some measure of hope. Which is perhaps the most valuable resource in the world right now.

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