There is a general agreement that episodes with extreme weather have become more frequent due to anthropogenic climate change. At the same time, there is still considerable uncertainty regarding the role of atmospheric dynamics in this context (Shepherd, 2014). The current paper investigates one specific dynamical phenomenon, namely the occurrence of Rossby wave resonance, and how it has changed over the past few decades. This is a fundamental topic in dynamical meteorology; it has garnered considerable attention in recent years, because the resonance mechanism may be responsible for the occurrence of extreme weather in specific episodes. Therefore, it is highly relevant to detect such resonance events in observations and assess potential trends. 

The diagnostic method employed by the authors makes two strong assumptions: 

• that the spatial scale of the waves is much smaller than the spatial scale of the background atmosphere, and 
• that midlatitude jets can function as perfect waveguides.  

Regrettably, both assumptions are highly questionable (Wirth, 2020; Harnik and Wirth, 2025).  

Consequently, it does not come as a surprise that the method yields results that are inconsistent with a more careful investigation that is not based on these assumptions (Wirth, 2020). Furthermore, Wirth and Polster (2021) point out that the application of the contested diagnostic method may conflate cause and effect, potentially leading to erroneous conclusions. To the best of my knowledge, my critiques, as outlined above, remain unopposed. Notably, the recent work by White and Admasu (2025) largely corroborates the concerns raised by Wirth and Polster (2021), further underscoring the need for a reevaluation of the methodology. Given the inappropriate nature of the diagnostic method, it is prudent to consider the possibility that the current paper’s findings might be spurious or incorrect.  

Despite the aforementioned critical issues, the contested diagnostic method remains widely used in parts of the scientific community (Petoukhov et al., 2013, 2016; Coumou et al., 2014; Stadtherr et al., 2016; Kornhuber et al., 2017 & 2017; Mann et al., 2017; Kornhuber et al., 2019; He et al., 2023; Li et al., 2024). 

Global warming has caused a rise of more than one degree worldwide since the beginning of the 20th century; on the Iberian Peninsula, the temperature has risen by more than two degrees in summer. Beyond the noticeable changes in the average climate, extreme weather events have many impacts on society and ecosystems. We know that over the last few decades there has been an increase in the intensity of heat waves, with clear trends in maximum temperatures, consistent with climate model estimates. The mechanisms by which climate extremes increase in response to global warming are currently being studied.

One of the mechanisms currently being studied is associated with the presence of very stable atmospheric waves on a planetary scale (Rossby waves of a certain wave number) that can amplify the behaviour of climate extremes. This mechanism is known as quasi-resonant amplification (QRA) of synoptic-scale waves, which contributes to the almost simultaneous generation of extreme weather events in several regions of the northern hemisphere that persist for long periods of time.

This study analyses observational and reanalysis databases to examine the evolution of this type of situation since the mid-20th century. The authors show a threefold increase in the frequency of resonance phenomena in the northern hemisphere summer and argue that this is consistent with resonance amplification associated with rising Arctic temperatures and land-sea contrast, both of which are the result of ongoing global warming.

This line of work has sparked some controversy and scientific debate in recent years, a good example of how science progresses. However, this work will undoubtedly contribute to clarifying the mechanisms by which there is an increase in the frequency and intensity of extreme events in the northern hemisphere summer and will contribute to a better understanding of how climate change influences the occurrence of extreme events and their attribution.