A new study finds that climate change has made a specific type of atmospheric wave pattern, known as quasi-resonant amplification (QRA), three times more frequent than in the mid-20th century. These wave events, which play a major role in driving extreme summer weather, now occur about three times per summer, up from once per summer in the 1950s.
Jet Stream Patterns Are Getting Stuck
QRA events develop when planetary waves in the atmosphere become amplified and stationary. Consequently, the jet stream may form large, persistent waves, which trap weather systems in place for extended periods. The result can be prolonged heatwaves, floods, or droughts. Past examples include the 2021 Pacific Northwest heatwave, the 2010 Russian heatwave and floods in Pakistan, and the 2003 European heatwave.
Human-Caused Climate Change a Key Driver
The study attributes the rise in QRA events to human-caused climate change, especially in the Arctic, which is warming much faster than the tropics. That warming reduces the temperature contrast, weakens the jet stream, and makes it more likely that atmospheric waves will become stuck.
Models May Be Missing a Crucial Factor
The researchers suggest that many long-range climate models underestimate the impact of summer extremes because they don’t fully account for QRA behavior. This point may help explain why observed increases in heatwaves, droughts, and floods have exceeded predictions.
El Niño Linked to Higher Risk
QRA patterns are also more likely following El Niño events. Because the summer of 2024 followed an El Niño, the study indicates that current conditions may favor more QRA-linked extremes.
Implications for the Future
The findings point to a growing risk of persistent and damaging summer weather events. Without major cuts in greenhouse gas emissions, these patterns are expected to become more frequent and intense.
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