Emissions Rise of Five CFCs Amid Montreal Protocol Progress

New research identifies a worrying trend: emissions of five ozone‑friendly chemicals are rising rapidly from 2010 to 2020. These are chlorofluorocarbons, or CFCs, whose use was largely halted by the Montreal Protocol. Some emissions arise from leaks during the manufacture of substitutes for CFCs. While these derivative emissions are allowed as exceptions in limited circumstances, the upward trajectory merits close watch and further scrutiny.

Researchers note that progress against older, prohibited uses has been strong. Yet attention is turning to minority sources whose emissions have become detectable as the main offenders fade from the skyline of public concern. The finding is part of a broader international effort to understand how replacements for CFCs behave in the real world and what this means for both the ozone layer and climate. This work has appeared in nature geology and underlines a cautious optimism about past gains alongside new questions about persistence and byproducts.

No immediate ozone threat, but greenhouse effect

Current assessments suggest these five CFCs do not pose an immediate risk to ozone recovery. Still, the steady rise could contribute meaningfully to the overall burden of ozone‑depleting chemicals if the trend continues unchecked.

Detected emissions are also warming the atmosphere and add to climate concerns. The total impact from these emissions is comparable to the 2020 CO2 output of a small country like Switzerland, amounting to about one percent of U.S. greenhouse gas emissions and roughly one‑thousandth of global totals, emphasizing their outsized influence despite small shares in overall statistics.

CFCs are well known for eroding the Earth’s protective ozone layer. They were once widely used in products such as aerosols, foams, packaging, solvents, and refrigerants. The Montreal Protocol effectively banned their production for these uses in 2010. Yet the treaty did not prohibit the ongoing use and creation of CFCs during the manufacture of other chemicals, a nuance that continues to shape emissions paths. Replacements like hydrofluorocarbons (HFCs) and, more recently, hydrofluoroolefins (HFOs) have been developed, but their production can still interact with CFCs in unforeseen ways.

This study centers on five CFCs with little or no current use: CFC-13, CFC-112a, CFC-113a, CFC-114a, and CFC-115. These compounds have atmospheric lifetimes from decades to many centuries. In terms of ozone impact, their emissions are roughly one‑tenth of the current emissions from CFC-11, one of the more abundant regulated CFCs.

Record abundance

Measurements gathered from 14 global sites, including AGAGE stations, and atmospheric transport models were used to assess abundance and emissions. After production for most uses was phased out in 2010, the global levels of these CFCs rose and reached record highs by 2020, signaling a gap between regulation and real‑world release pathways. This finding echoes the need for broader surveillance and tighter controls in underrepresented regions.

Three CFCs studied—CFC-113a, CFC-114a, and CFC-115—were found to increase in emissions, possibly linked to byproducts in the production of common HFCs used in refrigeration and air conditioning. That byproduct relationship underscores the complexity of fluorocarbon chemistry and the challenge of isolating singular sources within a global production network.

Researchers caution that the exact origins behind emissions from CFC-13 and CFC-112a remain unclear. There are scenarios where these compounds appear as intermediates, but current fluorocarbon processes do not clearly account for their presence in these roles. The study highlights gaps in global surveillance that hinder precise source attribution and calls for expanded, representative sampling across production hubs and transit routes.

Is it time to fine-tune the Montreal Protocol?

While the study did not pinpoint specific origins for rising emissions, it did observe a global upward trend whose implications could partly offset Montreal Protocol gains and contribute to warming. The researchers suggest reducing leachate from HFC production and ensuring proper handling of co‑produced CFCs as practical steps toward mitigation.

Given the ongoing atmosphere concentration rise for these chemicals, revisiting the Montreal Protocol’s scope may be prudent. The study notes that some replacements for CFCs may themselves carry unintended environmental footprints, warranting careful assessment of the full lifecycle of fluorocarbons and their substitutes.

These insights build a case for broader review and potential adjustments to international policy to prevent future offsets in ozone protection and climate progress. The message emphasizes that replacing ozone‑depleting chemicals with substitutes requires vigilance about the entire production chain and byproduct generation, not just the primary intended use.

Reference work: Nature Geology, 2023. These findings reflect ongoing collaborations among global researchers and atmospheric monitoring networks and stress the value of continuous, transparent data sharing for informed policy decisions.

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