Four before Forty – four challenges for the Montreal Protocol on World Ozone Day 2025
It’s almost 100 years since Thomas Midgley Jr. first synthesised chlorofluorocarbons (CFCs).
It was 1928 and he was working for General Motors, looking for a safe refrigerant to avoid using flammable or toxic alternatives. General Motors and Dupont soon began producing ‘Freon’ chemicals, which quickly dominated the market for refrigerants and also found wide use in aerosols and other applications such as foam-blowing.
Thomas Midgley Jr
Midgley, later described as a “one man environmental disaster” (he also invented leaded petrol), died 30 years before F Sherwood Rowland and Mario Molina published scientific studies demonstrating that when CFCs were exposed to UV light in the stratosphere, they disintegrated into chlorine atoms which destroyed ozone.
Although their findings were initially rejected by Dupont and other CFC producers, the scientific evidence basis and concern around the world continued to grow, ultimately resulting in the 1985 Vienna Convention for the Protection of the Ozone Layer.
By that time, British scientists Joe Farnam, Brian Gardiner and Jonathan Shanklin had proven that CFCs had already punched a hole in the ozone layer over Antarctica which, if left unchecked, would threaten all life on Earth.
On 16 September 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer was adopted under the framework of the Vienna Convention. It entered into force in 1989, with the initial controls requiring a freeze of CFC production and consumption in developed countries. These controls were quickly strengthened to a complete phase-out at the second Meeting of the Parties in 1990.
At that meeting, governments also agreed a financial mechanism and technology transfer to support developing countries, which lead to the establishment of the Multilateral Fund. This set the scene for success.
Over time, a series of amendments and adjustments were agreed by the Parties to the Montreal Protocol to strengthen action to reduce the consumption and production of most ozone-depleting substances (ODS). The Protocol achieved universal ratification in 2008 and has since been widely acknowledged as the world’s most successful environmental treaty, having set the ozone layer on a path to recovery.
Another reason for the “most successful” title was the almost accidental, but highly significant, climate protection achieved by the Montreal Protocol. CFCs and other ODS are potent greenhouse gases and, as such, the ozone treaty’s mandatory cuts to ODS production and consumption resulted in huge avoided emissions.
A seminal paper by Guus Velders and colleagues published in 2007 outlined “The importance of the Montreal Protocol in protecting climate”, demonstrating that the Montreal Protocol had already achieved about five to six times the emissions reductions expected from the Kyoto Protocol’s first commitment period. That same year, on the basis of its climate impact, Parties to the Montreal Protocol agreed to accelerate the hydrochlorofluorocarbon (HCFC) phase-out.
Just two years later, proposals to amend the treaty to control non-ozone-depleting hydrofluorocarbons (HFCs) were being tabled. Widely used as replacements for the ODS being phased out under the treaty, HFC production and consumption was rapidly increasing. As powerful greenhouse gases, the science soon demonstrated that HFC emissions could be equivalent to as much as 19 per cent of projected global CO2 emissions by 2050 unless action was taken.
It took until 2016 for the Montreal Protocol to agree the Kigali Amendment which, if fully implemented, will phase down HFC production and consumption by about 80 per cent by 2035, avoiding up to 0.4°C of warming by the end of the century. So far, 166 countries out of 198 have ratified the Amendment.
Next year we will celebrate the 10th anniversary of the Kigali Amendment and 2027 will mark the 40th anniversary of the Montreal Protocol itself. As we celebrate World Ozone Day in 2025, with the theme “From Science to Global Action”, it’s worth reflecting on what the science is showing now and what next steps Parties to the Montreal Protocol should be taking to protect and expand its legacy.
The science today clearly demonstrates several gaps, loopholes and areas for strengthening which could achieve significant additional climate and ozone mitigation.
So, as we approach the treaty’s 40th birthday, what does the Montreal Protocol’s “Four before Forty” challenge look like?
1. Reduce fluorochemical production emissions: Fluorochemical production is a significant source of ODS and HFC emissions, including CFCs and HCFCs that are used as feedstocks – chemical building blocks – for making other products such as fluorochemical refrigerants or fluoropolymers. Based on a large number published scientific papers, EIA has estimated that annual production-related emissions could be as high as 492 million tonnes of CO2-equivalent. In terms of climate impact, that’s like running an extra 130 coal-fired power stations for a full year, every year
Feedstocks are exempt from Montreal Protocol controls as emissions were previously thought to be negligible. However, recent scientific papers have demonstrated this is not the case, showing that feedstock emissions are actually responsible for some of the ‘unexpected’ CFC emissions being observed in the atmosphere. The Montreal Protocol needs to narrow and ultimately eliminate feedstock exemptions. As a first step, countries must significantly improve reporting and transparency around the fluorochemical industry.
2. Address banks of ODS and HFCs: Globally, large quantities of unwanted ODS and HFCs are held in ‘banks’ comprising end-of-life equipment, products and stockpiles. These banks represent a huge opportunity. In fact, the Montreal Protocol’s scientific experts have estimated that destroying the remaining banks of CFCs alone could be “the single most effective ozone-depletion and climate change mitigation option” for controlled ODS.
Under the Montreal Protocol, more than 100 developing countries have already received funding to draw up inventories of their ODS banks, as well plans for disposing of them. What we need now is to ensure adequate funding is available for these countries to implement the plans and to set up the necessary infrastructure and lifecycle refrigerant management to avoid further HFC banks accumulating in the future.
3. Tackle nitrous oxide (N2O) emissions: N2O is both an ozone-depleting substance and a potent greenhouse gas. As well as undermining the ozone layer’s recovery, emissions of N2O from human activity are already responsible for about 10 per cent of global warming to date. These emissions are also associated with serious human health risks, including increased rates of skin cancer and cataracts, due to greater UV exposure caused by N2O’s additional depletion of the ozone layer.
Despite these threats, little has been done to curb N2O emissions globally, which continue to increase at an accelerating rate. The Montreal Protocol, as the ozone treaty, is perhaps the best placed instrument to do something about this. The “low-hanging fruit” of industrial N2O emissions would be well-suited for controls under the Montreal Protocol and EIA is urging all countries to take immediate steps to better understand the challenge and protect the treaty’s legacy.
4. Align the Kigali Amendment with global climate targets: While the Kigali Amendment of 2016 established a solid framework for reducing HFC use, the escalating climate crisis demands faster and more ambitious action.
Since 2016, global HFC emissions have increased sharply, surpassing 1.2 billion tonnes of CO2-equivalent in 2020. At the same time, many countries have already taken accelerated action on HFCs, notably the EU which, by 2027, will have already met and surpassed the final phase-down step of the Kigali Amendment due in 2036.
The Kigali baselines agreed in 2016 allow many developing countries considerable scope to grow their HFC use, even after consumption levels are officially frozen. As such, raising ambition could not only accelerate progress but could also make the transition fairer across countries. Most crucially, a faster, deeper phase-down of HFCs is essential to align action under the Montreal Protocol with the Paris Agreement’s global goal of limiting warming to 1.5°C.
It took seven years to negotiate the Kigali Amendment on HFCs and already it is nearly 10 years since that agreement was adopted.
This is no time to be complacent – we are facing a global climate crisis and building consensus among 198 parties will take time, so let’s get going and get the first steps in place before we reach 40.
