Publication: Large impacts, past and future, of ozone-depleting substances on Brewer-Dobson circulation trends: a multimodel assessment
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2019-07-16
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American Geophysical Union
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Abstract
Substantial increases in the atmospheric concentration of well-mixed greenhouse gases (notably CO2), such as those projected to occur by the end of the 21st century under large radiative forcing scenarios, have long been known to cause an acceleration of the Brewer-Dobson circulation (BDC) in climate models. More recently, however, several single-model studies have proposed that ozone-depleting substances might also be important drivers of BDC trends. As these studies were conducted with different forcings over different periods, it is difficult to combine them to obtain a robust quantitative picture of the relative importance of ozone-depleting substances as drivers of BDC trends. To this end, we here analyze—over identical past and future periods—the output from 20 similarly forced models, gathered from two recent chemistry-climate modeling intercomparison projects. Our multimodel analysis reveals that ozone-depleting substances are responsible for more than half of the modeled BDC trends in the two decades 1980–2000. We also find that, as a consequence of the Montreal Protocol, decreasing concentrations of ozone-depleting substances in coming decades will strongly decelerate the BDC until the year 2080, reducing the age-of-air trends by more than half, and will thus substantially mitigate the impact of increasing CO2. As ozone-depleting substances impact BDC trends, primarily, via the depletion/recovery of stratospheric ozone over the South Pole, they impart seasonal and hemispheric asymmetries to the trends which may offer opportunities for detection in coming decades.
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©2019, the Authors. Artículo firmado por 15 autores. L. M. P. is most grateful for the hospitality of the Wartner family and the entire staff of the Eurotel Victoria in Les Diablerets, Switzerland, where the bulk of this manuscript was penned. He also acknowledges the continued support by the U.S. National Science Foundation (NSF). L. W. is supported by Grant JIH2308109 from Fudan University and Grant 41875047 from National Natural Science Foundation of China (NSFC). M. A. acknowledges funding from the Program Atraccion de Talento de la Comunidad de Madrid (2016-T2/AMB-1405) and the Spanish National Project STEADY (CGL2017-83198-R). N. B. was supported by the Met Office Hadley Centre Programme funded by BEIS and Defra and by the European Commission's Seventh Framework Programme StratoClim Project 226520. This research was also supported by the NZ Governments Strategic Science Investment Fund (SSIF) through the NIWA program CACV, and O. M. acknowledges funding by the New Zealand Royal Society Marsden Fund (Grant 12-NIW-006). Furthermore, Gang Zeng (from NIWA) performed the NIWA-UKCA simulations used in this study. All the data used here are publicly available via the CCMVal-2 and CCMI projects, as detailed in Morgenstern et al. (2010) and Morgenstern et al. (2017).