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- Title
On the Influence of Hydroxyl Radical Changes and Ocean Sinks on Estimated HCFC and HFC Emissions and Banks.
- Authors
Wang, Peidong; Solomon, Susan; Lickley, Megan; Scott, Jeffery R.; Weiss, Ray F.; Prinn, Ronald G.
- Abstract
Hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are potent greenhouse gases regulated under the Montreal Protocol and its amendments. Emission estimates generally use constant atmospheric lifetimes accounting for loss via hydroxyl radical (OH) reactions. However, chemistry‐climate models suggest OH increases after 1980, implying underestimated emissions. Further, HCFCs and HFCs are soluble in seawater and could be destroyed through in situ oceanic microbial activity. These ocean sinks are largely overlooked. Using a coupled atmosphere‐ocean model, we show that increases in modeled OH imply underestimated HCFC and HFC emissions by ∼10% near their respective peak emissions. Our model results also suggest that oceanic processes could lead to up to an additional 10% underestimation in these halocarbon emissions in the 2020s. Ensuring global compliance to the Protocol and accurate knowledge of contributions to global warming from these gases therefore requires understanding of these processes. Plain Language Summary: Man‐made hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) contribute to global warming, prompting worldwide agreement to control the production of these chemicals. It is important to estimate their emissions to ensure global compliance with the agreed phaseout. But correct emission estimation requires knowledge of different loss pathways. One major loss pathway of halocarbons is through chemical reactions with the atmospheric "scrubber" called OH. OH is difficult to measure and usually assumed to be constant with time. But some models suggest OH has increased, which implies increased emissions to match observed abundances. These halocarbons also dissolve into the oceans, where microbes may also metabolize them, but these processes are not included in current emission estimates. We show that if these halocarbons are being consumed in the oceans, this would also lead to an additional underestimation of human emissions. Confidence in the success in the Montreal Protocol and its Kigali amendment to reduce HFCs will therefore require a better understanding of both OH trends and ocean sinks, along with use of HFC and HCFC measurements. Key Points: Increasing OH suggested by Coupled Model Intercomparison Project Phase 6 models can lead to a 5%–7% underestimation in hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) emission estimations in 2005If there is significant ocean degradation through microbial activity, HCFC, and HFC emissions could be underestimated by up to 10%Our study suggests an uncertainty in the combined contribution to global warming from HCFCs and HFCs up to 15%–20% in the 2020s
- Subjects
KIGALI (Rwanda); HYDROXYL group; HYDROCHLOROFLUOROCARBONS; OCEAN; VIENNA Convention for the Protection of the Ozone Layer (1985). Protocols, etc., 1987 Sept. 15; GLOBAL warming
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 18, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL105472