Dr. Xueke Li and collaborators are the first to demonstrate a historical trend in planetary wave resonance over the past half-century. We find that the average number of resonance events per year has tripled since the advent of adequate upper atmospheric measurements in the mid-20th century, rising from about 1 event per year in 1950 to now about 3 per year.

Penn press release: https://penntoday.upenn.edu/news/extreme-summer-weather-patterns-have-tripled-1950s
Blog post: https://michaelmann.net/atmospheric-warming-and-planetary-wave-amplification/
Press coverage: https://vancouver.citynews.ca/2025/06/16/study-finds-planetary-waves-tripled-since-1950/