Increased frequency of planetary wave resonance events over the past half-century

Climate change is increasing the frequency and severity of boreal summer extreme weather events, many of which are inextricably linked to the phenomenon of resonant planetary wave amplification. However, due to incomplete knowledge of climate change impacts on these dynamical mechanisms, combined with limited observational records, significant uncertainties remain regarding the magnitude of such an impact. Our analysis reveals a threefold increase in this phenomenon over the past seven decades, closely tied to amplified Arctic warming and land–sea thermal contrast. We also observe increased prevalence of resonance events during the mature phase of strong El Niño events. These findings advance our understanding of how both human-caused climate change and natural climate variability impact mid-latitude atmospheric dynamics and extreme weather events.