Global and regional emissions of 1,2-dichloroethane derived from AGAGE and NOAA observations

Abstract. For the first time, we present long-term, ongoing atmospheric measurements of 1,2-dichloroethane (DCE, CH2ClCH2Cl) from the Advanced Global Atmospheric Gases Experiment (AGAGE) and National Oceanic and Atmospheric Administration (NOAA) global monitoring networks. DCE is an industrially produced, very short-lived chlorinated substance (Cl-VSLS) that has the potential to contribute chlorine to the stratosphere and cause ozone depletion. Compared to other Cl-VSLS, DCE is produced in higher volumes for its primary use as a feedstock in polyvinyl chloride (PVC) manufacture. This production has sustained annual mean mole fractions at the Earth’s surface of between 5 and 10 ppt during 2017–2023, making it the third most abundant Cl-VSLS. In this study we estimate mean global emissions for 2017–2023 of 453 [268, 638] Gg yr−1 using the AGAGE observations, and 525 [316, 734] Gg yr−1 using the NOAA observations. We also use AGAGE measurements to estimate regional emissions for northwest Europe (2.06 [1.31, 2.65] Gg yr−1) and California (0.23 [0, 0.37] Gg yr−1), two domains with sufficient observational coverage to enable this approach. Our global emissions estimates are consistent (within uncertainties) with the only previously published estimate by Hossaini et al. (2024), whereas our regional emission estimates are at least an order of magnitude smaller than those in that study. This suggests global total emissions may be well constrained, but their spatial distribution remains uncertain. Improved measurement coverage in key source regions of DCE could address that uncertainty and better constrain the contribution of DCE to ozone-depleting chlorine in the stratosphere.