No robust evidence of future changes in major stratospheric sudden warmings: a multi-model assessment from CCMI

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Ayarzagüena, Blanca, Polvani, Lorenzo M., Langematz, Ulrike, Akiyoshi, Hideharu, Bekki, Slimane, Butchart, Neal, Dameris, Martin, Deushi, Makoto, Hardiman, Steven C., Jöckel, Patrick, Klekociuk, Andrew, Marchand, Marion, Michou, Martine, Morgenstern, Olaf, O'Connor, Fiona M., Oman, Luke D., Plummer, David A., Revell, Laura, Rozanov, Eugene, Saint-Martin, David, Scinocca, John, Stenke, Andrea, Stone, Kane, Yamashita, Yousuke, Yoshida, Kohei, Zeng, Guang
• Other Authors: European Commission, Universidad Complutense de Madrid, German Research Foundation, National Science Foundation (US), Ministry of Business, Innovation, and Employment (New Zealand), Royal Marsden NHS Foundation Trust, Deep South National Science Challenge (New Zealand), German Climate Computing Center, Federal Ministry of Education and Research (Germany), Ministry of Environment (Japan), Environmental Restoration and Conservation Agency (Japan)
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union 2018
• Subjects: Arctic; O'Connor; polar night
• Online Access: http://hdl.handle.net/10261/185753; https://doi.org/10.5194/acp-18-11277-2018; https://doi.org/10.13039/501100001659; https://doi.org/10.13039/501100004629; https://doi.org/10.13039/100012139; https://doi.org/10.13039/100000001; https://doi.org/10.13039/501100000780; https://doi.org/10.13039/501100002347; https://doi.org/10.13039/501100002911

Major mid-winter stratospheric sudden warmings (SSWs) are the largest instance of wintertime variability in the Arctic stratosphere. Because SSWs are able to cause significant surface weather anomalies on intra-seasonal timescales, several previous studies have focused on their potential future change, as might be induced by anthropogenic forcings. However, a wide range of results have been reported, from a future increase in the frequency of SSWs to an actual decrease. Several factors might explain these contradictory results, notably the use of different metrics for the identification of SSWs and the impact of large climatological biases in single-model studies. To bring some clarity, we here revisit the question of future SSW changes, using an identical set of metrics applied consistently across 12 different models participating in the Chemistry–Climate Model Initiative. Our analysis reveals that no statistically significant change in the frequency of SSWs will occur over the 21st century, irrespective of the metric used for the identification of the event. Changes in other SSW characteristics – such as their duration, deceleration of the polar night jet, and the tropospheric forcing – are also assessed: again, we find no evidence of future changes over the 21st century. Blanca Ayarzagüena was funded by the European Project 603557-STRATOCLIM under the FP7-ENV.2013.6.1-2 programme and “Ayudas para la contratación de personal postdoctoral en formación en docencia e investigación en departamentos de la Universidad Complutense de Madrid”. Blanca Ayarzagüena and Ulrike Langematz wish to acknowledge the Deutsche Forschungsgemeinschaft (DFG) within the research programme SHARP under the grant LA 1025/15-1. Lorenzo M. Polvani is grateful for the continued support of the US National Science Foundation. The work of Neal Butchart, Steven C. Hardiman, and Fiona M. O'Connor was supported by the Joint BEIS/Defra Met Office Hadley Centre Climate Programme (GA01101). Neal Butchart and Steven C. Hardiman were supported by ...