Perspective on the shifting interannual variability of recent summer temperature modes in eastern China: Roles of Arctic sea-ice, Arctic Oscillation and Pakistan precipitation

Abstract Extreme heat events are observed increasingly in eastern China during recent high-summer (July–August), yet their underlying mechanisms remain unclear. Here we reveal considerable changes in local interannual temperature variability, manifesting as the enhancing south-north uniform warming (SNUW) mode and the disappearing south-north meridional dipole (SNMD) mode. The strengthening interannual SNUW variability is mainly associated with the increasing interannual variability of Pakistan convective precipitation and Arctic Oscillation, with the former linked to anthropogenic warming and the latter reflecting natural fluctuations. The decline in the interannual SNMD variability can be linked to the reduced interannual sea-ice variability in the Barents-Kara seas after 2004, which is associated with the disappearance of the Rossby wavetrain propagating towards eastern China. Moreover, projections from climate models suggest that future SNUW amplification will be dominated by increasing Pakistan convective precipitation variability; whereas the Arctic Oscillation influence is likely to be limited, featuring internal cyclical fluctuations of relatively small amplitude. Although models reproduce the SNUW mode reasonably well, their performance in simulating SNMD remains unsatisfactory, leaving the attribution of SNMD variability highly uncertain. Nevertheless, model projections consistently point to a further disappearance of the SNMD mode in the future. Together, these results highlight a fundamental reorganization of interannual temperature variability in eastern China under climate warming, and provide a new perspective for understanding the recent rapid changes in regional temperature variability.