LAUSR

Severe winter air pollution events, attributed to emissions from development, have increased in Beijing in recent decades. This study looks at how atmospheric conditions contribute and projects climate change will increase conditions favourable to such events. The frequency of Beijing winter severe haze episodes has increased substantially over the past decades1,2,3,4, and is commonly attributed to increased pollutant emissions from China’s rapid economic development5,6. During such episodes, levels of fine particulate matter are harmful to human health and the environment, and cause massive disruption to economic activities3,4,7,8,9,10,11,12,13,14,15,16, as occurred in January 201317,18,19,20,21. Conducive weather conditions are an important ingredient of severe haze episodes3,21, and include reduced surface winter northerlies3,21, weakened northwesterlies in the midtroposphere, and enhanced thermal stability of the lower atmosphere1,3,16,21. 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)22. The increased frequency is consistent with large-scale circulation changes, including an Arctic Oscillation upward trend23,24, weakening East Asian winter monsoon25,26, and faster warming in the lower troposphere27,28. Thus, circulation changes induced by global greenhouse gas emissions can contribute to the increased Beijing severe haze frequency.