Study Links Human-Caused Climate Change to Tripling of Extreme Weather Patterns

A recent study published in the Proceedings of the National Academy of Sciences reveals that the frequency of extreme weather-inducing planetary wave events has tripled since the 1950s due to human-caused climate change. These atmospheric waves, which affect the jet stream's waviness, can become amplified in a process known as quasi-resonant amplification (QRA), resulting in persistent weather patterns such as prolonged heat waves, droughts, and floods. Notable examples include the 2021 Pacific Northwest heatwave and the 2010 Russian heatwave.

Planetary waves, or Rossby waves, are large-scale atmospheric waves that play a crucial role in weather patterns by influencing the jet stream's path. Under certain conditions, these waves can become amplified and stationary, a phenomenon termed quasi-resonant amplification (QRA). This amplification results in persistent weather conditions, such as extended periods of heat or rainfall. The recent PNAS study highlights that the occurrence of QRA events has increased significantly over the past seven decades.

Study co-author Michael Mann, a climate scientist at the University of Pennsylvania, explains that the Arctic is warming three to four times faster than the global average. This rapid warming reduces the temperature gradient between the Arctic and the tropics, leading to a weakening of the jet stream. A weaker jet stream is more susceptible to becoming stationary, thereby increasing the likelihood of prolonged extreme weather events.

Several extreme weather events have been linked to QRA:

• 2021 Pacific Northwest Heatwave: In late June 2021, the Pacific Northwest experienced unprecedented temperatures, with Portland, Oregon, reaching 116°F (47°C) and Seattle, Washington, hitting 107°F (42°C). This event was associated with a "heat dome," a high-pressure system that trapped warm air over the region.

• 2010 Russian Heatwave: During the summer of 2010, Russia faced a severe heatwave, with Moscow recording temperatures up to 38.2°C (100.8°F). This event led to widespread wildfires and significant loss of life.

The study underscores a critical gap in current climate models, which may not fully account for the dynamics of QRA. This omission could lead to underestimations of the frequency and severity of extreme weather events. Climate scientist Jennifer Francis emphasizes the urgent need to reduce greenhouse gas emissions, as these persistent weather systems are expected to intensify, posing threats to agriculture and public health.

The increase in persistent extreme weather events has profound societal impacts:

• Agriculture: Prolonged droughts and heatwaves can devastate crops, leading to food shortages and economic losses for farmers.

• Public Health: Extended heatwaves increase the risk of heat-related illnesses and mortality, particularly among vulnerable populations.

• Infrastructure: Persistent heavy rainfall and flooding can damage infrastructure, leading to costly repairs and displacement of communities.

The research highlights the urgent need for improved understanding of atmospheric dynamics in a warming world and emphasizes the necessity of reducing greenhouse gas emissions to mitigate the increasing severity of persistent extreme weather events.