The Montreal Protocol and the Path to Ozone Layer Restoration by Leaf Kalikow

The ozone layer, which makes up part of the Earth’s stratosphere, is an area with a high concentration of ozone gas (O3); it serves as the Earth’s most effective means of absorbing harmful radiation, namely ultraviolet radiation, from the sun before it can make contact with the surface.[1] Excessive exposure to such radiation commonly results in the development of skin cancers; in 2012, a Harvard University study found that a minimal percent decrease in ozone can increase skin cancer incidence by three times that percent decrease.[2] It has been evident solely from the perspective of human welfare that governments across the world should take any initiatives that they can to protect the stability and strength of the ozone layer. As outlined by the Montreal Protocol, the biggest step toward restoring the layer is to cut down the use and emission of certain ozone-depleting substances, such as chlorofluorocarbons (CFCs), which have been prevalent refrigerants since 1928.[3] While phasing out CFCs, other refrigerants, most notably hydrofluorocarbons (HFCs), have been developed and commonly used, but there is a global concern that HFCs must be replaced as well to ensure ozone levels can return to past levels.[4] While science appears to support the shift away from HFC use in favor of other refrigerants with lower ozone-depleting properties, refrigeration history as well as the current ozone trajectory demonstrate that it is not reasonable to significantly eliminate them from use in the next few decades.

Following the rise of technological innovation of the Roaring Twenties, companies were looking for safer alternatives to common refrigerants.[5] Chemicals like ammonia and propane were no longer considered suitable; both substances are flammable, and ammonia is toxic upon inhalation.[6] CFCs were seen as the answer, as the chemicals were relatively easy to synthesize, not very flammable, nontoxic, and noncarcinogenic.[7] Unknown at the time, large amounts of CFCs escaping into the atmosphere would lead to the atrophy of the ozone layer.[8]

In the 1980s, fluctuations in the amount of ozone within the ozone layer were first being recorded and recognized.[9] Due to a growing, notable hole of ozone around the Antarctic pole, the Montreal Protocol was enacted in 1987 as a global agreement against further ozone depletion.[10] The goal of the agreement was for CFCs and other harmful ozone-depleting substances (ODS) to be phased out of use over time.[11] Over the next several decades, the participating nations agreed on further amendments to the protocol that would enact more stringent restrictions.

The most common substitute for CFCs has been HFCs that, while still mostly nontoxic and noncarcinogenic, act as a comparable substance and do not cause the degradation of the ozone layer at the same rate.[12] In fact, the ozone layer has shown signs of restoration over the past decade, and with the current trajectory, there are hopes of returning to ozone levels similar to those of the 1970s within the next thirty years. Despite this improvement, HFCs contribute to global warming at similar rates as CFCs, causing amendments to the Montreal Protocol to call for the severe reduction of the use of HFCs.[13] In 2019, the Kigali amendment to the Montreal Protocol called for over 80% reduction in HFC use by 2047.[14] While HFCs might not be ideal, they have proven to allow ozone restoration due to their lower depletion rates, and with how little is currently in the atmosphere relative to other gases, it seems easier to cut back on other greenhouse gas emissions over cutting back HFC use.

One oversight of the Montreal Protocol is the environmental toll of the repeated phase out of replacement substances. For instance, while it was good to replace CFCs, replacing them with HFCs that would later be phased out releases a greater amount of greenhouse gases into the atmosphere. Learning from that mistake, the substitute for HFCs should be suitable in the long run without requiring replacement in the near future again. However, none of the potential replacements seem like appropriate alternatives.

There are three main viable replacements moving forward. The first is the return to ammonia, as it is the cheapest and most thermally efficient option while refrigeration systems have become more advanced over time and the threat of ammonia catching fire in improved systems is much lower than it was before.[15] A second option is carbon dioxide, which is a much better environmental option over HFCs, but due to unideal thermal properties, a cooling system functioning on carbon dioxide would require a very large pressure and could be impractical on a large scale.[16] A third option, the most promising, is to use hydrofluoroolefins (HFOs), which would contribute to ozone depletion and global warming at a lower rate than HFCs but higher than carbon dioxide.[17] The best qualities of HFOs are their zero ozone-depleting potential and minimal global warming contribution, but being fairly new, there could be other side effects of their use that scientists have not yet recognized.[18] Notably, Mercedes-Benz refuses to switch to HFO use in their cars as they have found HFOs have a higher flammability than the HFCs they currently use.[19]

The current push is for HFOs to be the replacement for HFCs, but it might be too soon to make that call. If HFOs are used on a larger scale, there could be downsides that lead them to be phased out in the next amendment to the Montreal Protocol. Seeing that it does provide a definitive solution, it would be best for governments to implement policies that incentivize research into HFOs and other options. Since the holes in the ozone layer have been shrinking for several years now greatly due to the initial shift away from CFCs, the most logical decision is to not set restrictions on HFCs until enough research has been done on alternatives. Economically, this would allow firms with extensive refrigerant use to save on investing in new refrigerants that could require potential replacement. Perhaps, if a company wants to try using a new refrigerant, governments should let them serve as a test group to determine the extent of negative effects, but they should not all be required to switch to something that could harm their companies in the long run without seeing any positive environmental result. Considering multiple perspectives, amending the Montreal Protocol to reverse the restriction on HFCs set by the Kigali amendment is the best option at the moment to prevent bad environmental consequences of a premature decision.

[1] National Geographic Society. “Ozone Layer,” May 9, 2011.

[2] Reuell, Peter. “Concerns about Climate Change, Health.” Harvard Gazette, July 30, 2012.

[3] “History of Chlorofluorocarbons.”

[4] Wilson, Stephen. “Explainer: Hydrofluorocarbons Saved the Ozone Layer, so Why Are We Banning Them?” The Conversation, November 2, 2017.

[5] “History of Chlorofluorocarbons.”

[6] Cardin, Matt. “Ammonia As a Refrigerant: Pros and Cons.” Ammonia As a Refrigerant: Pros and Cons | Just Venting, n.d.

[7] “History of Chlorofluorocarbons.”

[8] “History of Chlorofluorocarbons.”

[9] NASA. “World of Change: Antarctic Ozone Hole.” 2019.

[10] “World of Change: Antarctic Ozone Hole.”

[11] “The Montreal Protocol Evolves to Fight Climate Change.” UNIDO, January 1, 2019.

[12] Wilson, Stephen. “Explainer: Hydrofluorocarbons Saved the Ozone Layer, so Why Are We Banning Them?”

[13] “Chlorofluorocarbons (CFCs) and Hydrofluorocarbons (HFCs).” Minnesota Pollution Control Agency, n.d.

[14] “The Montreal Protocol Evolves to Fight Climate Change.” UNIDO, January 1, 2019.

[15] “Alternatives to HFC.” KEEP IT COOL, TOMPKINS!, 2018.

[16] “Alternatives to HFC.”

[17] “Alternatives to HFC.”

[18] “Alternatives to HFC.”

[19] “Alternatives to HFC.”

4 thoughts on “The Montreal Protocol and the Path to Ozone Layer Restoration by Leaf Kalikow

  1. Leaf, this was a great read! You bring up a really important point that it is not always wise to jump on the latest discovery or innovation to solve environmental problems, as we’ve seen time and time again how human discoveries and innovations — though valuable and important — have often led to problems of their own. You make a strong case for reversing the Kigali amendment’s restrictions on HFCs; indeed, decisions made without sufficient research or consideration for potential impacts on the environment and economy can have unfortunate outcomes. I agree that governments should implement policies incentivizing research into HFOs and other alternatives. Even if research doesn’t find a safer alternative, it could at least lead to a better understanding of the potential consequences of widespread HFO use. While it’s hard for me to imagine that we’ll find a 100% safe and environmentally friendly alternative to HFCs, I think it’s worthwhile for governments to invest in research on its next replacement, even if flawed. Understanding the potential risks of this replacement can prepare us to take preventative steps to minimize safety risks and negative environmental impacts when the time comes to phase out HFCs.

  2. Thank you for writing this informative piece, Leaf. I knew about the issue with CFCs and HFCs, but had never heard of HFOs. I agree that the government should encourage firms to perform pseudo-experiments using different alternatives to HFCs, such as ammonia and HFOs, and attempting to mitigate HFC escaping into the atmosphere. As there is no clear cut solution here and no obvious best option, we should look for the best out of the bad bunch through trial and error and fund our brightest scientists in their continued search for another alternative.

  3. Hi Leaf! This was a really interesting take on a topic that I rarely hear about. I would like to hear more about what the Kigali amendment actually effects, seeing as HFCs are still in use. I agree that research into HFOs is important, but I also think that an important part of mitigating the impacts of refrigerants is efficiency. In all likelihood, we will never find a perfect refrigerant that does not contribute to greenhouse gas. That is why I think it is more important to invest in programs that seek to decrease the amount of refrigerant needed, such as organizations that pay to retrofit homes of low income people with better insulation. This also leads to a more equitable outcome, as older homes will likely continue to go without upgrades and the gap in costs of cooling will only widen with time. Especially in the southern states, cooling in the summer can become incredibly expensive, and simple upgrades like double-paned windows can make a huge difference in the energy and refrigerant expended.

  4. Wow, what an interesting dilemma! I remember reading about CFCs in AP Enviro but not about any modern alternatives that were being explored. It seems odd to me that they would make it a priority to reduce the use of HFCs to reduce greenhouse gas emissions when there are so many other greenhouse-gas related issues that, as you pointed out, have a larger impact. I wonder if it seemed like a natural and relatively easy goal/transition as compared with the other options to reduce greenhouse gas emissions. If companies do not decide to explore other options for themselves, do you think that governments will start to invest more in researching alternatives? Are there any interesting out-of-the-box options that you’ve heard of? I always like to look at problems & solutions from as many angles and approaches as possible, especially when I don’t agree with some of them. Also, it’s crazy that we can see a giant hole in the ozone (and crazy lucky it didn’t appear somewhere even more harmful to humans) so of course, we did something about that, but greenhouse gases and climate change are so much “harder” to tackle/for people to believe…

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