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The HFC challenge: Can the Montreal Protocol continue its winning streak?

  • Since the Montreal Protocol was signed in 1987, countries have phased out most of the ozone-damaging gases, but their replacements, the HFCs, are powerful greenhouse gases that contribute to climate change.
  • In 2016, national delegates agreed on the Kigali Amendment to the Montreal Protocol, which calls for cutting the production and use of HFCs by 80–85% by the late 2040s. The amendment entered into force at the start of 2019, with the goal of avoiding additional warming by up to 0.4°C (0.72 °F) by the end of the century.
  • The future success of the Kigali Amendment faces several challenges, including countries inaccurately estimating their emissions of HFCs, the need for affordable alternatives, and the fact that the major producers of HFCs (China, the United States and India) have not yet signed the treaty.
  • Scientists and policymakers continue to address these challenges, with the U.S. and China having recently announced their intent to ratify the treaty. Also, the U.S. this week signaled its commitment to aggressively cutting the use and production of HFCs via a new, proposed Environmental Protection Agency rule.

In 1987, a one-seat, one-pilot, “Gary Powers [style] spy plane,” loaded with sophisticated scientific instruments screamed into the lower stratosphere above Antarctica at 200 meters per second. Its mission: determine the cause of a mysterious ozone hole in Earth’s atmosphere.

“Basically, the story got told right there — almost immediately,” recalls David Fahey, an atmospheric chemist with the U.S. National Oceanic and Atmospheric Administration (NOAA), stationed in Boulder, Colorado. He was one of the scientists who worked through that night analyzing the data.

The team’s landmark findings confirmed that chlorofluorocarbons (CFCs), ubiquitous coolants used for decades as refrigerants and in foam production, were the culprits behind Earth’s thinning ozone layer.

Spurred on by accumulating scientific evidence, the world’s nations had crafted the 1987 United Nations Montreal Protocol to control the production and consumption of ozone-depleting chemicals. Since then, 197 countries and the European Union have ratified the binding treaty, and CFC levels have steadily declined in the atmosphere.

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In September 2019, the ozone hole was the smallest it had been since 1982 — marking a triumph for science and global diplomacy.

“The Montreal Protocol is the most successful international treaty on the environment of all time,” says Neil Harris, an atmospheric chemist at the University of Cranfield, U.K. “It is working fully, and it continues to work.”

But success didn’t come without tremendous labor on the part of industry and nations — along with diligent monitoring by scientists, acting something like traffic cops with radar guns, measuring trace gases, and helping protect the ozone layer down to today. That due diligence is largely an untold story, with the treaty still actively evolving to meet new atmospheric pollution challenges as they arise.

A NOAA ozonezonde, an instrument used to help scientists monitor the Antarctic ozone hole, ascends over the South Pole in a time-lapse photo taken Oct. 21, 2020. Researchers have tracked ozone-depleting chemicals in the atmosphere using satellites, planes, ships, balloons, and ground stations for decades — without that scientific effort the expanding ozone hole might never have been detected. Image by Yuya Makino/IceCube.

Climate good news and bad news

The Montreal Protocol provided an added bonus for humanity: CFCs and their substitutes, the hydrochlorofluorocarbons (HCFCs), in addition to being ozone-damaging, are also powerful greenhouse gases. So the phasing out of these chemicals benefited Earth’s climate too: From 1990–2010, the ban on harmful refrigerants reduced carbon dioxide equivalent emissions by an estimated 135 billion metric tons.

But there’s a catch to this success story, one playing out in diplomatic circles today. To replace the CFCs and HCFCs, manufacturers developed a new generation of coolants, the hydrofluorocarbons, or HFCs. These chemicals don’t damage the ozone layer, but it turns out that they are bad for the climate — very bad. Many cause between 1,400 and 5,000 times more warming in the atmosphere than carbon dioxide, according to a scientific finding that came in time to prevent their pouring into the atmosphere at dangerous levels.

Consequently, in 2016, national delegates agreed on the Kigali Amendment to the Montreal Protocol, which calls for cutting the production and use of HFCs by 80–85% by the late 2040s. The amendment entered into force at the start of 2019, with the goal of avoiding additional warming by up to 0.4° Celsius (0.72° Fahrenheit) by the end of the century.

Delegates from more than 200 countries gather at the annual Montreal Protocol meeting. Image by Kiara Worth/IISD/ENB.
Delegates during the HFC Management Contact Group gather during the 2016 Meeting of the Parties in Kigali, Rwanda. Image by Kiara Worth/IISD/ENB.

On its path to conserving the ozone layer, the Montreal Protocol has faced many similar hurdles, including an unexpected and jarring increase in CFC emissions —a possible treaty violation by Chinese factories — discovered and corrected in just the last few years.

Now, a new, albeit similar, set of challenges could impede the implementation of the Kigali Amendment, as scientists and policymakers grapple on how to overcome them. To date, neither China nor the United States have ratified Kigali, and they are the largest producers of HFCs — though the election of President Joe Biden and cooperation from China could soon change that.

“We want to make sure to lock in those climate benefits we got from the treaty in the past,” says NOAA’s Stephen Montzka, “and make sure they don’t go away.”

Researcher Jen Morse hikes up to Niwot Ridge carrying gas collection canisters. Image by Jane Palmer.

Taking the atmosphere’s pulse: Learning from CFC-11

Every week, Jen Morse, a research technician at the University of Colorado Boulder, places four large gas canisters in her backpack and treks to a small green shack on Niwot Ridge, a blustery slope in the U.S. Rocky Mountains. Once there, she traps the thin mountain air in her flasks, which she then delivers for analysis to NOAA’s Global Monitoring Division in Boulder.

Similar flask collections take place around the world — at observatories, on airplanes and ships. The goal: collect air not tainted by local pollution to provide a measure of the “background” atmosphere. Once the samples arrive at the lab, scientists from the gas monitoring group run them through their instruments to determine global levels of dozens of CFCs, HCFCs and HFCs.

“There’s so many science stories [found] in the amazing resource that comes from regularly measuring the global atmosphere, taking its pulse on a week-to-week, month-to-month, decade-to-decade basis,” Montzka says.

An example: Montzka had watched global levels of CFCs steadily fall for years, showing that countries were phasing out ozone-depleting gases in accordance with the Montreal Protocol. But then, one day in 2013, he received a nasty surprise: The levels of one gas, trichlorofluoromethane, known as CFC-11, were not dropping as fast as they had been. Someone, somewhere, was producing it, in violation of the treaty.

Steve Montzka positions a tube in a snow hole at the South Pole. Air trapped between snow crystals provides a historical record of atmospheric trace gases over the past century. Image courtesy of Steve Montzka.
Members of the Scientific Assessment Panel attending the 2018 Montreal Protocol meeting. L-R: Stephen Montzka, Bonfils Safari, Paul Newman, and John Pyle. Image by IISD/ENB.

It took some time for the scientific community to identify that the new emissions were coming from China. Once notified, the Chinese government apparently quickly clamped down on the illegal production of CFC-11, as the levels of the gas are now declining closer to expectations. The incident highlights the importance of ongoing atmospheric monitoring in ensuring countries adhere to the protocol.

Now, the same rules are being applied to the Kigali Amendment, with signatory nations committed to reporting their production and consumption of HFCs, and relying on producers, exporters and importers to provide accurate statistics about what they’ve made and shipped.

“The Amendment relies on industry doing its job and collecting a comprehensive set of statistics, and governments faithfully reporting these values,” says Matthew Rigby, an atmospheric chemist at the U.K.’s University of Bristol.

The CFC-11 example shows that sometimes, however, production isn’t reported, and currently — and of global concern — there is insufficient infrastructure in place to identify when there’s a mismatch between a country’s reports and actual gas emissions.

Jen Morse tests wind direction outside her “lab,” the green shack on Niwot Ridge. Image by Jane Palmer.
Jen Morse waits while mountain air fills the gas canisters. Image by Jane Palmer.

While Montzka identified that emissions of CFC-11 were increasing globally and got a hint that some of the increase was from eastern Asia, it was regional monitoring stations on Jeju Island in South Korea, and Hateruma Island in Japan, operated by the Advanced Global Atmospheric Gases Experiment (AGAGE) network that offered vital clues as to the precise point of origin of the increasing emissions. Using that data, an international research team was able to determine that about half the global increase of CFC-11 was coming from the Chinese provinces of Shandong and Hebei.

Regional monitoring stations exist in the U.S. and Europe and, in response to the recent crisis, China is now developing its own regional monitoring network. But there is presently no regional monitoring in India, the Middle East, Africa, Russia or South America.

“So, we don’t really have much idea about what’s going on in these places in terms of their greenhouse gas or ozone-depleting substance emissions,” Rigby says. “We’d really like to see a more extensive measurement network in the future.”

The Jungfraujoch research station, high in the Swiss Alps, at 3,450 meters. Image courtesy of

An ominous oddity 

High in the Swiss Alps, at 3,450 meters (11,320 feet), atmospheric chemist Martin Vollmer takes inventory of the atmosphere.

Vollmer, an atmospheric scientist at Empa/Swiss Federal Laboratories for Materials Science and Technology, works at the Jungfraujoch research station, perched on a glaciated saddle between the Jungfrau and Mönch peaks, where he monitors trace gases making up less than 1% of Earth’s atmosphere, including CFCs, HCFCs and HFCs — data summaries of which are reported twice yearly to Montreal Protocol delegates.

Although the alpine setting appears pristine, with its snow-capped, jagged peaks rising above a verdant valley floor, wafts of polluted air reach the station from nearby industrial centers, with telltale bad news for Earth’s climate. Over the years, while Vollmer has watched levels of most ozone-depleting gases fall, levels of HFCs are rising.

He and his colleagues have found “interesting” levels of a particular HFC coming from northern Italy. This gas, HFC-23, could be considered the bête noire of the HFC chemical class: each HFC-23 molecule is 12,700 times more effective at warming the climate than one molecule of carbon dioxide, and has the longest lifetime of all the HFCs — staying aloft for nearly 230 years.

Oddly, industry doesn’t create HFC-23 as a refrigerant or for any other use; its production is mostly incidental. When companies make hydrochlorofluorocarbon-22, (HCFC-22), HFC-23 is an unwanted byproduct. The Montreal Protocol called for a complete ban on the use of HCFCs as refrigerants in developed countries from Jan. 1, 2020, due to their ozone-damaging potential, but there’s a loophole: HCFC-22 can still be manufactured as a feedstock, or a starter chemical, used to make other chemicals such as Teflon.

This series of images shows the Antarctic ozone hole on the day of its annual maximum depletion in 1979, 1987, 2006, and 2010, as measured by the ozone measuring instrument on the Aura satellite. Images courtesy NASA Ozone Hole Watch.

“The Montreal Protocol put its main focus on the production and consumption of CFCs originally, and there was no focus on byproducts in manufacture or feedstock,” Vollmer explains. “There’s a cleaning up of these issues that needs to be done in the Montreal Protocol.”

When a country signs the Kigali Amendment, it agrees to destroy HFC-23 made during chemical manufacturing “to the extent practicable using technologies approved by the parties,” and to report on its HFC-23 emissions as a byproduct in HCFC production. But scientists like Vollmer have discovered that countries have not estimated their emissions of this gas accurately. Between 2008 and 2010, the Swiss scientists were able to determine that Italy emitted between 26 and 56 metric tons of HFC-23 annually, while the official Italian inventory estimated just two to three metric tons were coming from the region.

In 2015, China and India announced ambitious plans to decrease HFC-23 emissions and they stated two years later they had almost completely eliminated HFC-23 atmospheric releases. As a result, scientists expected to see an almost-complete halt in growth of the gas, “but actually what we saw was the emissions carried on, going up as they had been before,” Rigby reveals.

The discovery of this discrepancy, published in 2020, again highlights the importance of persistent atmospheric monitoring for the future success of the Kigali Amendment. Monitoring is necessary to ensure that countries can make accurate estimates regarding their production of HFCs and also to check the honesty of their reporting, Rigby says.

“I think a major challenge for the Kigali Amendment is in the reporting of the production of HFCs and ensuring compliance,” he says. “It is still a somewhat unresolved issue that we’re going to need to keep an eye on if Kigali is going to be successful.”

Meg Seki, Acting Executive Secretary, Ozone Secretariat at the virtual meeting of the Montreal Protocol parties in November 2020. Image by IISD/ENB.

U.S., China, India: Committing to the cause

Another barrier stands in the way of accomplishing Kigali’s goals. As of mid-April 2021, 119 countries have signed the Kigali Amendment, but the major HFC producers — China, India and the U.S. — have not yet signed. China produces more than 60% of the world’s HFC gases today and, in 2018, the U.S. produced 155 million metric tons of HFCs. The European Union’s HFC output for 2018 was less than two-thirds of this amount.

“For the Kigali Amendment to be successful, we want to have universal ratifications, but getting to this universal ratification is a challenge in itself,” says Megumi Seki, acting executive secretary of the U.N. Environment Programme’s Ozone Secretariat, headquartered in Nairobi, Kenya.

But recent news is encouraging: In April 2021, Chinese President Xi Jinping indicated that his nation, the world’s largest producer of refrigerants, will accept the Kigali Amendment and move toward ratification. Also, when Joe Biden assumed the U.S. presidency, he signed an executive order seeking U.S. Senate ratification of the Kigali Amendment.

In 2019, the peak extent of the ozone hole over Antarctica was only 16.4 million square kilometers (6.3 million square miles). If the Montreal Protocol parties stay on track with their commitments, the ozone hole could return to pre-1980 levels by the 2060s. NASA Earth Observatory image by Joshua Stevens, using data courtesy of NASA Ozone Watch.

During the Obama administration, air conditioning and refrigeration manufacturers worked with the U.S. government toward a plan to phase out the use of HFCs with high global warming potential, but that effort stalled under the Trump administration. Still, even with the Kigali Amendment unratified, the U.S. Congress enacted the American Innovation and Manufacturing (AIM) Act, in late 2020, which requires mandatory reductions in HFCs in alignment with the Kigali Amendment’s schedule. Now, AIM will help each segment of the U.S. HFC market smoothly transition to climate-friendly alternatives.

“Having suitable alternatives to the ozone-depleting refrigerants was a key contributor to the success of the Montreal Protocol,” Seki says, and in the last two decades, industry has been investigating and developing HFC alternatives.

The latest generation of coolants, called hydrofluoroolefins (HFOs), neither damage the ozone layer nor contribute to climate warming, and encouragingly, Vollmer has tracked the rise of these compounds in the atmosphere. In 2011, for example, he didn’t find any HFO-1234yf in his samples, but by 2018, it was showing up in 71% of the air analyzed at Jungfraujoch. “From an atmospheric perspective, the replacement of the Kigali substances with HFOs is rather good,” Vollmer says.

2018 Montreal Protocol Meeting: L-R: Ping-Fei Shieh and Wen-Cheng Hu, Industrial Technology Research Institute (ITRI); and Stephen Montzka, Scientific Assessment Panel. Image by IISD/ENB.

‘Start and strengthen’

If, or when, China and the U.S. ratify the Kigali Amendment, it will hopefully motivate other countries, including India, to sign on. Just this week, the U.S. Environmental Protection Agency proposed a tough new rule cutting the use and production of HFCs. Meanwhile, the scientists who provide scientific assessments to the Montreal Protocol continue striving to improve HFC monitoring.

“There is a push for improving our capabilities, so that we can improve our understanding of regional changes with better coverage throughout the globe,” Montzka says.

At Jungfraujoch, researchers are expanding monitoring to measure more HFCs, while also devising a metric to determine whether the Kigali Amendment is being successful in terms of reducing HFC amounts being emitted. “The countries are the ones who measure production, sales and trades, but those numbers need to be verified and validated and that’s where we come in,” Vollmer says.

Meg Seki, Acting Executive Secretary, Ozone Secretariat (right) and Vincent Biruta of Rwanda, President of the Meetings of the Parties in Kigali, Rwanda (center) in 2016. Image by Kiara Worth/IISD/ENB.

For policymakers who are preparing new environmental treaties, the key takeaway from the Montreal Protocol is that it is a living, ever-evolving document. The first iteration of the protocol in 1987 only called for the phaseout of five CFCs and three halons. Thirty years later, the treaty now covers about 100 ozone-depleting gases and 18 HFCs through an ever-evolving process of amendments and adjustments. “We sometimes refer to this as the ‘start and strengthen’ approach,” Seki says.

The healing of the ozone layer, and success of the protocol, has been an unfolding, rather than overnight, triumph, and it’s likely the Kigali Amendment will see a similar process. “I am sure the Kigali Amendment is just the first step on the phasing down of HFCs and that we’ll see further amendments and adjustments which will continue to strengthen it,” concludes Rigby.

Banner image: The Jungfraujoch research station in the Swiss Alps. Image courtesy of

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