Montreal Protocol – Cabot Institute for the Environment blog

The last ozone-layer damaging chemicals to be phased out are finally falling in the atmosphere

Posted on June 18, 2024 by amanda.woodman-hardy

The high-altitude AGAGE Jungfraujoch station in Switzerland is used to take measurements of Earth’s atmosphere.
Jungfrau.ch

Since the discovery of the ozone layer, countries have agreed and amended treaties to aid its recovery. The most notable of these is the Montreal protocol on substances that deplete the ozone layer, which is widely regarded as the most successful environmental agreement ever devised.

Ratified by every UN member state and first adopted in 1987, the Montreal protocol aimed to reduce the release of ozone-depleting substances into the atmosphere. The most well known of these are chlorofluorocarbons (CFCs).

Starting in 1989, the protocol phased out the global production of CFCs by 2010 and prohibited their use in equipment like refrigerators, air-conditioners and insulating foam. This gradual phase-out allowed countries with less established economies time to transition to alternatives and provided funding to help them comply with the protocol’s regulations.

Today, refrigerators and aerosol cans contain gases like propane which, although flammable, does not deplete ozone in Earth’s upper atmosphere when released. However, ozone-friendly alternatives to CFCs in some products, such as certain foams used to insulate fridges, buildings and air-conditioning units, took longer to find. Another set of gases, hydrochlorofluorocarbons (HCFCs), was used as a temporary replacement.

A collection of used refrigerators. — HCFCs can leak to the atmosphere from discarded fridges.
RichardJohnson/Shutterstock

Unfortunately, HCFCs still destroy ozone. The good news is that levels of HCFCs in the atmosphere are now falling and indeed have been since 2021 according to research I led with colleagues. This marks a major milestone in the recovery of Earth’s ozone layer – and offers a rare success story in humanity’s efforts to tackle climate-warming gases too.

HCFCs v CFCs

HCFCs and CFCs have much in common. These similarities are what made the former suitable alternatives.

HCFCs contain chlorine, the chemical element in CFCs that causes these compounds to destroy the ozone layer. HCFCs deplete ozone to a much smaller extent than the CFCs they have replaced – you would have to release around ten times as much HCFC to have a comparable impact on the ozone layer.

But both CFCs and HCFCs are potent greenhouse gases. The most commonly used HCFC, HCFC-22, has a global warming potential of 1,910 times that of carbon dioxide, but only lasts for around 12 years in the atmosphere compared with several centuries for CO₂.

As non-ozone depleting alternatives to HCFCs became available it was decided that amendments to the Montreal protocol were needed to phase HCFCs out. These were agreed in Copenhagen and Beijing in 1992 and 1999 respectively.

This phase-out is still underway. A global target to end most production of HCFCs is set for 2030, with only very minor amounts allowed until 2040.

Turning the corner on a bumpy road

Our findings show that levels of HCFCs in the atmosphere have been falling since 2021 – the first decline since scientists started taking measurements in the late 1970s. This milestone shows the enormous success of the Montreal protocol in not only tackling the original problem of CFCs but also its lesser known and less destructive successor.

Two graphs side by side showing a the climate warming and ozone-destroying influence of HCFCs declining from 2021. — The influence of HCFCs on the atmosphere is set to fall steadily.
Western et al. (2024)/Nature

This is very good news for the ozone layer’s continuing recovery. The most recent scientific prediction, made in 2022, anticipated that HCFC levels would not start falling until 2026.

Despite HCFC levels in the atmosphere going in the right direction, not everything has been smooth sailing in the phase-out of ozone-depleting substances. In 2019 a team of scientists, including myself, provided evidence that CFC-11, a common constituent of foam insulation, was still being used in parts of China despite the global ban on production.

The United Nations Environment Programme also reported that HCFCs were illegally produced in 2020 contrary to the phase-down schedule.

In 2023, I and others showed that levels of five more CFCs were increasing in the atmosphere. Rather than illegal production, this increase was more likely the result of a different process: a loophole in the Montreal protocol which allowed CFCs to be produced if they are used to make other substances, such as plastics or non-ozone depleting alternatives to CFCs and HCFCs.

Some HCFCs at very low levels in the atmosphere have also been shown to be increasing or not falling fast enough, despite few or no known uses.

Most of the CFCs and HCFCs still increasing in the atmosphere are released in the production of fluoropolymers – perhaps best known for their application in non-stick frying pans – or hydrofluorocarbons (HFCs).

HFCs are the ozone-friendly alternative that was developed and commercialised in the early 1990s to replace HCFCs, but their role as a potent greenhouse gas means that they are subject to international climate emission reduction treaties such as the Paris agreement and the Kigali amendment to the Montreal protocol.

The next best alternative to climate-warming HFCs is a matter of ongoing discussion. In many applications, it was thought that HFCs would be replaced by hydrofluoroolefins (HFOs), but these have created their own environmental problems in the formation of trifluoroacetic acid which does not break down in the environment and, like other poly- and per-fluorinated substances (PFAS), may pose a risk to human health.

A column of air-conditioning units attached to the exterior of a building. — HFOs enable air-conditioners to use less electricity than competing alternatives.
AndriiKoval/Shutterstock

HFOs are at least more energy-efficient refrigerants than older alternatives like propane, however.

Hope for the future

In discovering this fall in atmospheric levels of HCFCs, I feel like we may be turning the final corner in the global effort to repair the ozone layer. There is still a long way to go before it is back to its original state, but there are now good reasons to be optimistic.

Climate and optimism are two words rarely seen together. But we now know that a small group of potent greenhouse gases called HCFCs have been contributing less and less to climate change since 2021 – and look to set to continue this trend for the foreseeable future.

With policies already in place to phase down HFCs, there is hope that environmental agreements and international cooperation can work in combating climate change.

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This blog is written by Cabot Institute for the Environment member Dr Luke Western, Research Associate in Atmospheric Science, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

How we traced ‘mystery emissions’ of CFCs back to eastern China

Posted on June 5, 2019April 13, 2023 by janet.crompton

Since being universally ratified in the 1980s, the Montreal Protocol – the treaty charged with healing the ozone layer – has been wildly successful in causing large reductions in emissions of ozone depleting substances. Along the way, it has also averted a sizeable amount of global warming, as those same substances are also potent greenhouse gases. No wonder the ozone process is often held up as a model of how the international community could work together to tackle climate change.

However, new research we have published with colleagues in Nature shows that global emissions of the second most abundant ozone-depleting gas, CFC-11, have increased globally since 2013, primarily because of increases in emissions from eastern China. Our results strongly suggest a violation of the Montreal Protocol.

A global ban on the production of CFCs has been in force since 2010, due to their central role in depleting the stratospheric ozone layer, which protects us from the sun’s ultraviolet radiation. Since global restrictions on CFC production and use began to bite, atmospheric scientists had become used to seeing steady or accelerating year-on-year declines in their concentration.

Ozone-depleting gases, measured in the lower atmosphere. Decline since the early 1990s is primarily due to the controls on production under the Montreal Protocol. AGAGE / CSIRO

But bucking the long-term trend, a strange signal began to emerge in 2013: the rate of decline of the second most abundant CFC was slowing. Before it was banned, the gas, CFC-11, was used primarily to make insulating foams. This meant that any remaining emissions should be due to leakage from “banks” of old foams in buildings and refrigerators, which should gradually decline with time.

But in that study published last year, measurements from remote monitoring stations suggested that someone was producing and using CFC-11 again, leading to thousands of tonnes of new emissions to the atmosphere each year. Hints in the data available at the time suggested that eastern Asia accounted for some unknown fraction of the global increase, but it was not clear where exactly these emissions came from.

Growing ‘plumes’ over Korea and Japan

Scientists, including ourselves, immediately began to look for clues from other measurements around the world. Most monitoring stations, primarily in North America and Europe, were consistent with gradually declining emissions in the nearby surrounding regions, as expected.
But all was not quite right at two stations: one on Jeju Island, South Korea, and the other on Hateruma Island, Japan.

These sites showed “spikes” in concentration when plumes of CFC-11 from nearby industrialised regions passed by, and these spikes had got bigger since 2013. The implication was clear: emissions had increased from somewhere nearby.

To further narrow things down, we ran computer models that could use weather data to simulate how pollution plumes travel through the atmosphere.

Atmospheric observations at Gosan and Hateruma monitoring stations showed an increase in CFC-11 emissions from China, primarily from Shandong, Hebei and surrounding provinces. Rigby et al, Author provided

From the simulations and the measured concentrations of CFC-11, it became apparent that a major change had occurred over eastern China. Emissions between 2014 and 2017 were around 7,000 tonnes per year higher than during 2008 to 2012. This represents more than a doubling of emissions from the region, and accounts for at least 40% to 60% of the global increase. In terms of the impact on climate, the new emissions are roughly equivalent to the annual CO₂ emissions of London.

The most plausible explanation for such an increase is that CFC-11 was still being produced, even after the global ban, and on-the-ground investigations by the Environmental Investigations Agency and the New York Times seemed to confirm continued production and use of CFC-11 even in 2018, although they weren’t able to determine how significant it was.

While it’s not known exactly why production and use of CFC-11 apparently restarted in China after the 2010 ban, these reports noted that it may be that some foam producers were not willing to transition to using second generation substitutes (HFCs and other gases, which are not harmful to the ozone layer) as the supply of the first generation substitutes (HCFCs) was becoming restricted for the first time in 2013.

Bigger than the ozone hole

Chinese authorities have said they will “crack-down” on any illegal production. We hope that the new data in our study will help. Ultimately, if China successfully eliminates the new emissions sources, then the long-term negative impact on the ozone layer and climate could be modest, and a megacity-sized amount of CO₂-equivalent emissions would be avoided. But if emissions continue at their current rate, it could undo part of the success of the Montreal Protocol.

The network of global (AGAGE) and US-run (NOAA) monitoring stations. Luke Western, Author provided

While this story demonstrates the critical value of atmospheric monitoring networks, it also highlights a weakness of the current system. As pollutants quickly disperse in the atmosphere, and as there are only so many measurement stations, we were only able to get detailed information on emissions from certain parts of the world.

Therefore, if the major sources of CFC-11 had been a few hundred kilometres further to the west or south in China, or in unmonitored parts of the world, such as India, Russia, South America or most of Africa, the puzzle would remain unsolved. Indeed, there are still parts of the recent global emissions rise that remain unattributed to any specific region.

When governments and policy makers are armed with this atmospheric data, they will be in a much better position to consider effective measures. Without it, detective work is severely hampered.

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This blog is written by Cabot Institute member Dr Matt Rigby, Reader in Atmospheric Chemistry, University of Bristol; Luke Western, Research Associate in Atmospheric Science, University of Bristol, and Steve Montzka, Research Chemist, NOAA ESRL Global Monitoring Division, University of Colorado. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Listen to Matt Rigby talk about CFC emissions on BBC Radio 4’s Inside Science programme.

Independent verification of the UK’s greenhouse gas report: holding the Government to account

Posted on November 7, 2016April 6, 2023 by janet.crompton

In the early hours of October 15th, negotiators from over 170 countries finalised a legally binding accord, designed to counter the effects of climate change by way of phasing down emissions of Hydrofluorocarbons (HFCs). These gases, introduced to replace the ozone-depleting CFCs and HCFCs for which the original Montreal Protocol was drafted, are typically used as coolants in air-conditioning systems. Unfortunately, like their predecessors, they are potent greenhouse gases, whose climate forcing effect per molecule is often many thousands of times greater than carbon dioxide.

The Kigali deal, named after the Rwandan city in which it was struck, is a compromise between rich countries, whose phase-out plan will begin as early as 2019, and poorer nations, for many of whom the relief of air-conditioning has only just become available. India, for instance, will not make its first 10% emissions cut until 2032.

Delegates celebrate the finalisation of the Kigali deal. Credit: COP 22

When the deal was finally completed, there was much celebration and relief. Against the ironic drone of several large air-conditioning units, brought in to maintain a comfortable temperature on a stifling Rwandan night, US Secretary of State John Kerry labelled the deal ‘a monumental step forward’.

However, as with the much lauded Paris Agreement, the success of this landmark piece of legislation will rely heavily on accountability. Each nation reports its greenhouse gas emissions, including HFCs, to the United Nations Framework Convention on Climate Change (UNFCCC). It is from these reports that a nation’s progress in cutting emissions can be assessed.

Here at the University of Bristol’s Atmospheric Chemistry Research Group (ACRG), we use atmospheric measurements of these greenhouse gases, in combination with an atmospheric transport model, to independently estimate emissions. Recently, we have used such an approach to estimate emissions of HFC-134a, the most abundant HFC in the global atmosphere. Observations of this gas were taken from the Mace Head Observatory, which can be found on the rugged West Coast of Ireland.

When we compared our emission estimates with those the UK government reported to the UNFCCC, a significant discrepancy was observed; between 1995 and 2012, the UNFCCC numbers are consistently double those derived independently.

The Mace Head observatory is ideally positioned to intercept air mass from the UK and Europe. Credit – University of Bristol

Via collaboration with DECC (Department of Energy and Climate Change), the government body that was previously responsible for the construction of the UKs annual emissions report, we were granted access to the model used to estimate HFC-134a emissions. Analysis of this model uncovered a number of assumptions made about the UK’s HFC markets, which in practice did not add up. Our work has led to a reassessment of the HFC-134a inventory by the government, and a subsequent lowering of the reported emission totals in the 2016 report.

In the wake of the Kigali and Paris agreements, both of which will require accurate reporting of emissions, our work is amongst the first examples of how independent verification can directly influence inventory totals. However, this study represents just the tip of the iceberg. Across the Kyoto ‘basket’ of gases determined to have an adverse effect on climate, inconsistencies between reporting methods are common place. A more concerted effort is therefore required to harmonise inventory reports with independent studies.

In countries such as the UK, where networks capable of measuring these gases already exist, the focus will be on improving the accuracy and reducing the uncertainty of our emission estimates; a step which will likely involve the addition of new sites, new instrumentation and significant investment.

Perhaps more importantly, these methods of independent verification must now be extended to regions where such infrastructure does not currently exist. Emissions from many of these countries are anticipated to rise sharply in the coming years, but are poorly monitored.

In July, researchers from the ACRG returned from Northern India, after two months studying greenhouse gas emissions from the FAAM research aircraft.

The Atmospheric Research Aircraft from the Facility for
Airborne Atmospheric Measurements (FAAM), established by NERC and the Met Office as a facility for the
UK atmospheric science community. Credit – FAAM

The utilisation of different data platforms is likely to play an essential role in enhancing the global network of greenhouse gas observations. It is the responsibility of the research community to ensure continued growth of the measurement network, and improve the availability of independent emission estimates required to verify the success (or otherwise) of climate legislation.

This blog was written for the Policy Bristol Blog by Dan Say, PhD student, Atmospheric Chemistry
Research Group, School of Chemistry, University of Bristol.

35 years monitoring the changing composition of our atmosphere

Posted on November 4, 2013April 20, 2023 by janet.crompton

I work on an experiment that began when the Bee Gees’ Stayin’ Alive was at the top of the charts. The project is called AGAGE, the Advanced Global Atmospheric Gases Experiment, and I’m here in Boston, Massachusetts celebrating its 35-year anniversary. AGAGE began life in 1978 as the Atmospheric Lifetimes Experiment, ALE, and has been making high-frequency, high-precision measurements of atmospheric trace gases ever since.

At the time of its inception, the world had suddenly become aware of the potential dangers associated with CFCs (chlorofluorocarbons). What were previously thought to be harmless refrigerants and aerosol propellants were found to have a damaging influence on stratospheric ozone, which protects us from harmful ultraviolet radiation. The discovery of this ozone-depletion process was made by Mario Molina and F. Sherwood Rowland, for which they, and Paul Crutzen, won the Nobel Prize in Chemistry in 1995. However, Molina and Rowland were not sure how long CFCs would persist in the atmosphere, and so ALE, under the leadership of Prof. Ron Prinn (MIT) and collaborators around the world, was devised to test whether we’d be burdened with CFCs in our atmosphere for years, decades or centuries.

Fig 1. The AGAGE network

ALE monitored the concentration of CFCs, and other ozone depleting substances, at five sites chosen for their relatively “unpolluted” air (including the west coast of Ireland station which is now run by Prof. Simon O’Doherty here at the University of Bristol). The idea was that if we could measure the increasing concentration of these gases in the air, then, when combined with estimates of the global emission rate, we would be able to determine how rapidly natural processes in the atmosphere were removing them.

Fig 2. Mace Head station on the West coast of Ireland

Thanks in part to these measurements, we now know that CFCs will only be removed from the atmosphere over tens to hundreds of years, meaning that the recovery of stratospheric ozone and the famous ozone “hole” will take several generations. However, over the years, ALE, and now AGAGE, have identified a more positive story relating to atmospheric CFCs: the effectiveness of international agreements to limit gas emissions.

The Montreal Protocol on Substances that Deplete the Ozone Layer was agreed upon after the problems associated with CFCs were recognised. It was agreed that CFC use would be phased-out in developed countries first, and developing countries after a delay of a few years. The effects were seen very rapidly. For some of the shorter-lived compounds, such as methyl chloroform (shown in the figure), AGAGE measurements show that global concentrations began to drop within 5 years of the 1987 ratification of the Protocol.

Figure 3. Concentrations of methyl chloroform, a substance banned under the Montreal Protocol, measured at four AGAGE stations.

Over time, the focus of AGAGE has shifted. As the most severe consequences of stratospheric ozone depletion look like they’ve been avoided, we’re now more acutely aware of the impact of “greenhouse” gases on the Earth’s climate. In response, AGAGE has developed new techniques that can measure over 40 compounds that are warming the surface of the planet. These measurements are showing some remarkable things, such as the rapid growth of HFCs, which are replacements for CFCs that have an unfortunate global-warming side effect, or the strange fluctuations in atmospheric methane concentrations, which looked like they’d plateaued in 1999, but are now growing rapidly again.

The meeting of AGAGE team members this year has been a reminder of how important this type of meticulous long-term monitoring is. It’s also a great example of international scientific collaboration, with representatives attending from the USA, UK, South Korea, Australia, Switzerland, Norway and Italy. Without the remarkable record that these scientists have compiled, we’d be much less informed about the changing composition of the atmosphere, more unsure about the lifetimes of CFCs and other ozone depleting substances, and unclear as to the exact concentrations and emissions rates of some potent greenhouse gases. I’m looking forward to the insights we’ll gain from the next 35 years of AGAGE measurements!This blog was written by Dr Matt Rigby, Atmospheric Chemistry Research Group, University of Bristol.

Matt Rigby