Title: Weather Conditions Conducive to Beijing Severe Haze More Frequent under Climate Change 

Journal: Nature Climate Change, doi: 10.1038/NCLIMATE3249 

Authors: CAI W. -J., K. Li, H. Liao*, H. -J.Wang, and L. -X. Wu, 2017

Abstract: The frequency of Beijing winter severe haze episodes has increased substantially over the past decades, and is commonly attributed to increased pollutant emissions fromChina’s rapid economic development. During such episodes, levels of fine particulate matter are harmful to human health and the environment, and cause massive disruption to economic activities, as occurred in January 2013. Conducive weather conditions are an important ingredient of severe haze episodes, and include reduced surface winter northerlies weakened northwesterlies in the midtroposphere, and enhanced thermal stability of the lower atmosphere. How such weather conditions may respond to climate change is not clear. Here we project a 50% increase in the frequency and an 80% increase in the persistence of conducive weather conditions similar to those in January 2013, in response to climate change. The frequency and persistence between the historical (1950–1999) and future (2050–2099) climate were compared in 15 models under Representative Concentration Pathway 8.5 (RCP8.5). The increased frequency is consistent with large-scale circulation changes, including an Arctic Oscillation upward trend, weakening East Asian winter monsoon, and faster warming in the lower troposphere.Thus, circulation changes induced by global greenhouse gas emissions can contribute to the increased Beijing severe haze frequency.