The super‐heat wave in eastern China during July–August 2013: a perspective of climate change

Abstract

ABSTRACTEastern China suffered a record‐breaking heat wave throughout almost all of summer, during 2013. Recent studies found a discernible impact of anthropogenic forcing on this extreme heat wave event. In this study, we investigate the role of multidecadal variability (MDV) in regulating the likelihood of the 2013 heat wave event. Using the ensemble empirical mode decomposition (EEMD) method, we decomposed the heat wave index series into three components: (1) a non‐linear secular trend (ST), representing the long‐term anthropogenic warming; (2) MDV; and (3) the residual high‐frequency variability. For the period 1873–2013, the linear trend of heat wave strength (HW‐S, defined as the July–August mean temperatures) was 0.06 °C per decade, mainly because of the contribution of ST. MDV plays an important role in regulating changes over decades. ST and MDV together form a changing climate background (CB) for extreme events. The 2013 heat wave event would be almost impossible under the pre‐industrial CB but becomes likely under the long‐term warming background, with a return period of longer than 103 years. When the positive phase of MDV is added to the secular warming background (the current CB), the return period of a super‐heat wave such as the 2013 event becomes about 42 (12–103) years. The Atlantic Multidecadal Oscillation (AMO) shows significant correlation with the MDV component of the HW‐S in Shanghai. The correlation pattern between the AMO and MDV of July–August temperatures over the Northern Hemisphere is analysed to explain the AMO–Shanghai relationship. It is suggested that the likelihood of such an extreme event will increase with further long‐term climate warming, modified by low‐frequency oceanic variations such as the AMO.