This devastating synthetic gas is spreading: 3,500 times more impactful than CO2 by Cédric Depnd, December 23, 2024, Techno-science.net
Source: Journal of Quantitative Spectroscopy and Radiative Transfer
HFC-125, a synthetic gas, is in the spotlight. Recent measurements from space reveal a true explosion in its atmospheric concentration. This industrial compound could significantly amplify already critical climate issues.
Hydrofluorocarbons, of which HFC-125 is a part, were initially designed to replace CFCs, which are responsible for ozone layer depletion. Although they have no impact on the ozone layer, their effect on global warming is alarming. With a global warming potential 3,500 times greater than CO2 over 100 years, HFC-125 is a significant heat trap.
Primarily used in air conditioning systems, refrigerators, and fire extinguishers, HFC-125 is released into the atmosphere through industrial emissions. Its chemical stability makes it a persistent gas, remaining in the atmosphere for several decades.
For the first time, a team from the University of Waterloo, in collaboration with the Canadian Space Agency, measured its concentration from space. The ACE-FTS satellite, in orbit since 2004, provided precise data between 11 and 25 kilometers (approximately 7 to 15.5 miles) altitude.
The results are striking: in just two decades, HFC-125 levels have increased tenfold. This rapid surge reflects the growing demand for cooling technologies, particularly in emerging countries where such equipment is becoming commonplace.
HFC-125’s climate impact is not limited to its mere presence. By trapping infrared radiation, it intensifies the greenhouse effect and directly contributes to the rise in global average temperatures.
To address this trend, the international community adopted the Kigali Amendment to the Montreal Protocol. This agreement aims to gradually reduce the production and use of HFCs, promoting more environmentally friendly alternatives.
However, researchers emphasize that the effectiveness of these measures depends on their swift and widespread implementation. Without immediate action, HFC-125 concentrations will continue to grow, threatening to worsen an already fragile climate.
If regulations prove effective, as was the case with CFCs, scientists hope to observe a gradual decline in this gas in the coming years. But time is of the essence to counter its effects and avoid irreversible climate disruptions.
What is global warming potential (GWP)?
Global warming potential (GWP) measures a greenhouse gas’s impact on global warming. It compares the ability of a molecule to trap heat in the atmosphere relative to carbon dioxide (CO₂), which serves as the baseline.
This value is calculated over a specific period, often 20, 100, or 500 years. For example, in the context of this study, a GWP of 3,500 means the gas traps 3,500 times more heat than the same amount of CO₂ over 100 years.
Gases with high GWP values, such as HFC-125, are particularly concerning. Their long lifespan amplifies their impact, as they persist in the atmosphere for decades or even centuries.
By accounting for GWP, international regulations like the Kigali Amendment aim to reduce the use of such substances to limit their contribution to global warming.
The first satellite measurements of HFC-125 by the ACE-FTS: Long-term trends and distribution in the Earth’s upper troposphere and lower stratosphere by R. Dodangodage, P.F. Bernath, C. Boone, J.J. Harrison, M. Lecours , M. Schmidt, S.A. Montzka, I. Vimont, M. Crotwell, January 2025, Journal of Quantitative Spectroscopy and Radiative Transfer Volume 330, 10921
https://doi.org/10.1016/j.jqsrt.2024.109218
Highlights
- •HFC-125 VMR has been measured from orbit for the first time using ACE-FTS.
- •HFC-125 VMR global distribution above and in the troposphere (11 km) is determined.
- •HFC-125 VMRs are increasing exponentially.
Abstract
HFC-125 (CFCHF, pentafluoroethane) volume mixing ratios (VMRs) have been determined for the first time using infrared absorption spectra from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) from 2004 to 2024. These VMRs provide global altitude-latitude VMR distributions. A VMR time series for HFC-125 has also been calculated and compared to values from in situ discrete flask measurements conducted by the National Oceanic and Atmospheric Administration Earth System Research Laboratory. The abundance of HFC-125 is currently experiencing exponential growth. ACE data shows a growth rate of 3.47 ± 0.05 ppt/year in the past six years.
Introduction
Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs) are commonly used in air conditioning and fire suppression systems. R-410 A, a well-known HFC blend consisting of 50% HFC-32 and 50% HFC-125, is widely used in refrigeration systems and heat pumps [1], and HFC-125 is widely used as a firefighting agent [2]. Initially, CFCs were used in commercial applications until Molina and Rowland [3] demonstrated that photolysis of CFCs in the stratosphere releases chlorine atoms, leading to the destruction of stratospheric ozone. This discovery was confirmed with the detection of the Antarctic ozone hole in the mid-1980s [4]. In response, the Montreal Protocol [5] was established in 1987 to mitigate stratospheric ozone depletion by phasing out the production and consumption of ozone-depleting substances (ODSs). CFCs have been phased out globally, and their replacements, HCFCs, will be phased out by 2030. HFCs have emerged as replacements for HCFCs due to their minimal or zero ozone-depleting potential (ODP). However, like the CFCs and HCFCs they replace, HFCs have significantly high global warming potentials (GWPs). Molecules with high GWPs contribute to an increase in surface temperature, indirectly affecting stratospheric ozone. The Kigali amendment [6] was added to the Montreal Protocol in 2019 to phase down the production and consumption of HFCs with large GWPs. The main sinks for HFCs are reactions with OH radicals in the troposphere and stratosphere, as well as reactions with O(D) in the stratosphere. Studies have shown HFC-125 has a GWP of 3500 (100-year) [7], 3170 (100-year) [8] or 3820 (100-year) [2] and a lifetime of 30 years [2].
The Advanced Global Atmospheric Gases Experiment (AGAGE) and the National Oceanic and Atmospheric Administration (NOAA) offer ground based in situ measurements and discrete flask measurements, respectively, of HFCs, including HFC-125, through their global networks. These studies reveal that HFC-125 abundances in the atmosphere and their growth rates are increasing rapidly [9], [10], [11], [12], [13]. O’Doherty et al. [9] documented the rapid growth of HFC-125 based on the AGAGE and the System for Observation of halogenated Greenhouse gases in Europe (SOGE) observations, reporting a global average of 5.6 ppt at the beginning of 2008 and a growth rate of 16% per year. Simmonds et al. [10] calculated cumulative emissions for two 5-year periods (2006–2010 and 2011–2015); HFC-125 shows a 91.7% increase between the two periods, and at the end of 2015, HFC-125 emissions have reached 31 ± 14 Gg yr−1 and the global mean mole fraction of HFC-125 was 18.4 pmol mol−1 [10]. Simmonds et al. [11] examined the surface-to-surface transport of five HFCs (HFC-152a, -134a, -143a, -32, and -125) using AGAGE observations at Mace Head, Ireland, from 2005 to 2012. USA emissions of individual HFCs were estimated using the interspecies correlation method, with HFC-125 serving as the reference molecule, and the NAME dispersion model. The study concludes that the five HFCs could collectively contribute approximately 201 Tg-COeq yr−1 to atmospheric radiative forcing in 2011–2012.
Hu et al. [14] provided a comprehensive estimate of U.S. emissions of three CFCs, two HCFCs, and six HFCs, including HFC-125, based on flask air samples collected across North America from 2008 to 2014. Their findings reveal that the total CO-equivalent emissions of CFCs and HCFCs have decreased, while the aggregated emissions of HFCs remained relatively unchanged over this period. Fang et al. [15] have compiled a comprehensive inventory of China’s HFC production, consumption, and emissions from 2005 to 2013, revealing a rapid increase in emissions in China. Flask and in situ measurements conducted across seven sites in China from 2011 to 2017 were utilized to estimate HFC emissions and changes [16]. The study concludes that HFC-125 contributes 39% to China’s total HFC emissions. HFC measurements from Hateruma Island in East Asia indicate occasional short-term enhancements and seasonal variations [17]. Kuyper et al. [18] estimate the 2017 HFC-125 emissions at Cape Point, South Africa, to be 0.8 (0.5–1.2) Gg yr−1, with the mole fractions increasing throughout the year. Say et al. [19] estimated several HFC emissions over India using air samples collected from an aircraft campaign during June and July of 2016. Brunner et al. [20] used four independent inverse models to estimate emissions of HFC-134a and HFC-125 over Europe, which are the two HFCs contributing the most to global warming. HFC-134a emerged as the primary contributor to HFC radiative forcing (44%), with HFC-125 (18%) surpassing HFC-23 (15%) as the second largest contributor [2]. Flerlage et al. [21] provide a review of bottom-up and top-down emissions of HFCs in different parts of the world, including Africa, Asia, Australia, Europe, Northern America, Latin America, and the Caribbean.
Updated NOAA and AGAGE measurements are updated quadrennially in the World Meteorological Organization (WMO) Scientific Assessment of Ozone Depletion reports [2], and are used to derive best estimate global emission estimates. HFC emissions in 2020 were 1.22 ± 0.05 Gt CO-eq. yr−1, 19% higher than in 2016, and of this total, HFC-125 was responsible for 28%. HFC-125 is the second largest contributor to the radiative forcing, which is 18% of the overall radiative forcing due to HFCs. Because of the substantial and increasing contributions of HFC-125 to atmospheric direct radiative forcing, a complete picture of climate forcing can only be supplied with continued measurements of this HFC. We report the first HFC-125 measurements by solar infrared absorption spectroscopy from orbit.
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Conclusion
For the first time, satellite-based remote sensing retrievals of HFC-125 using ACE-FTS were utilized to examine its distribution and trend on a global scale. The results of our analysis indicate that there has been a significant increase in atmospheric concentrations of HFC-125 since 2004. This accelerated growth of HFC-125 VMRs is consistent with the in situ and discrete flask measurements provided by NOAA and AGAGE. …
