Impact of stratospheric water vapor enhancements caused by CH₄and H₂O increase on polar ozone loss

Abstract

[1] Possible causes of a future increase in stratospheric H 2 O are increasing tropospheric methane levels and a rise in tropospheric H 2 due to leakages from a possible increased integration of hydrogen into the energy supply system. Here we quantify the direct chemical impact of potential future stratospheric H 2 O increases on Arctic ozone loss using the cold Arctic winter 2004/2005 as the basis for our study. We present simulations with the three-dimensional chemistry transport model CLaMS using enhanced stratospheric H 2 O values. Previous studies emphasized that increasing H 2 O concentrations cause stratospheric cooling, and some have suggested that this could significantly increase halogen-induced polar ozone loss. The impact of both increased stratospheric H 2 O values and decreased temperatures on simulated ozone depletion is investigated. Assuming an average increase of water vapor in the lower polar stratosphere of ≈0.58 ppmv (averaged over equivalent latitudes ≥ 65°N, from 400-550 K potential temperature and from December to March) and in addition decreased temperatures (−0.2 K) yields at most 6.8 DU (≈11 %) more accumulated ozone loss in mid-March for the Arctic polar winter 2004/2005 compared to the ozone loss for undisturbed conditions. The assumed H 2 O enhancement in future decades is in the range of current model predictions. Considering in addition the decrease of the future chlorine loading (−40 %) of enhanced H 2 O values (see above) yields at most 3.4 DU (10 %) of accumulated ozone loss in springtime compared to current H 2 O values. The impact of a potential future hydrogen economy alone (assuming an averaged increase of 0.18 ppmv H 2 O in the lower stratosphere) on springtime accumulated ozone loss is found to be negligible (at most 2.5 DU (4 %)) in this study.Citation: Vogel, B., T. Feck, and J.-U. Grooß (2011), Impact of stratospheric water vapor enhancements caused by CH 4 and H 2 O increase on polar ozone loss,

The sensitivity of stratospheric ozone changes through the 21st century to N<sub>2</sub>O and CH<sub>4</sub>

“…6b. This is in contrast to the findings of Kirk-Davidoff et al (1999), Feck (2008) and Vogel et al (2011), who found that cooler temperatures resulting from increases in water vapour lead to enhanced heterogeneous chlorine chemistry and subsequent ozone loss. It is likely that because we focus on the 2090s decade in our analysis, when stratospheric chlorine levels are very low, heterogeneous chemistry is no longer of significance to polar ozone depletion.…”

Impact of a possible future global hydrogen economy on Arctic stratospheric ozone loss

“…70 The chemical ozone destruction over the Arctic in early 2011 was, for the first time in the observational record, comparable to that in the Antarctic ozone hole with a maximum accumulated ozone loss of up to approximately 130 DU. 71 In a study recently published by Vogel et al 57 (2011) using the 3-dimensional chemistry transport model CLaMS, 72- 57 For both scenarios S2 and S4, the calculated ozone loss is much smaller than the existing variability of ozone loss observed in cold Arctic winters. 70 It should be noted that simulations focusing on the stratospheric impact of additional hydrogen economy differ from each other not only in the model or method used, but also in the assumptions related to chemical or physical processes.…”

“…4,6,57 Because the H 2 leakage rate deduced by Tromp et al 3 (2003) was assessed to be unrealistically high, 1,2,4,6,47 the impact of a potential hydrogen economy on the stratospheric ozone loss is obviously overestimated. The findings of other studies 4,6,56,57,67 vary somewhat as a result of using different models and techniques. However, all these studies suggest that a future potential hydrogen economy would have a minor impact on Arctic ozone loss.…”

“…Because of the uncertainties discussed above, in most studies the impact of a future hydrogen-based economy on the atmosphere is analyzed using scenarios reflecting low, intermediate, and/or very high (worst-case) hydrogen emission rates. 2,3,6,56,57 Fig . 2 shows the range of projected hydrogen production rates with the ''IIASA-SRES B1-H2'' scenario as a clear upper limit.…”

“…Hitherto, different types of atmospheric models and techniques at various levels of complexity ranging from ozone loss proxies, 6 2-dimensional models 3,4 or 3-dimensional chemistry transport models 56,57,67 have been used to determine the impact of enhanced stratospheric H 2 O caused by an increased atmospheric H 2 burden on ozone loss processes in the Arctic. Ozone loss proxies 6 are based on an empirical relationship between the Arctic ozone column loss and the total volume of air exposed to temperatures below a critical value controlling PSC formation.…”