Unusual Jet Stream Patterns Are Causing Extreme Weather, Study Suggests

Wildfires, droughts, and floods are all connected.

Climate change is not a predicted threat but a catastrophe currently afflicting humankind. The summer of 2018 was a testament to this fact: The season witnessed record heat waves around the planet, unprecedented flooding events, and wildfires unmatched in magnitude and scope. California’s wildfires, which continue to ravage the state, are the worst in its history, and even the chilled Arctic Circle experienced historic outbreaks.

In a video recently released by Pennsylvania State University, atmospheric science professor Michael Mann, Ph.D., explains that extreme weather events, like the kind seen this summer, are becoming more prevalent because of climate change and are consistent with what climate models have previously predicted. While droughts, floods, and fires may seem like disconnected events, they are all connected through a particular phenomenon wrought by human-caused climate change: unusual jet stream patterns.

These unusual jet stream patterns, Mann and his colleagues explain in a Science paper published in October, ignite Quasi-Resonant Amplification events — moments of extreme weather tha manifest as the sort of calamities that plagued the summer. A jet stream pattern is one that is undulating dramatically north and south as it crosses the northern hemisphere. Here, the team determined that when a jet stream has big “peaks and troughs,” extreme weather events will soon follow.

Jet stream on July 12, 2018 showing large undulations.

What is Causing Unusual Jet Stream Patterns

Mann explains that there’s a push and pull between the “warming effect of increasing greenhouse gas concentrations” and the “regional cooling effect of these atmospheric pollutants that we call aerosols.”

As greenhouse gases accumulate, more unusual jets stream patterns occur — the team notes that if greenhouse emissions continue to escalate at their current rate, Quasi-Resonant Amplification events will increase by 50 percent by the end of the century.

Ironically, an effort to improve human health could make this situation worst. Anthropogenic — human-linked — aerosols are linked to industrialization since they emerge from the burning of coal and oil. As air pollutants, they’re very unhealthy for people, so a number of European and North American nations have worked to remove aerosol-generating pollutants. However, while still definitely bad for us, aerosols reflect heat away from the planet and can balance out the heating effect of greenhouse gases.

Concentrations of carbon monoxide (in orange/red) emerged from California's wildfires, here seen between July 30 and August 7.


Analysis conducted by Mann and his colleagues revealed that removing aerosols from the atmosphere should mitigate increases in Quasi-Resonant Amplification events because the difference in warming between the Arctic and mid-latitudes will diminish. However, without aerosols, greenhouse warming at mid-latitude levels may only get worse — causing tropical storms and heatwaves to become stronger.

The only real solution here, Mann posits, is for nations to dedicate themselves to cutting down greenhouse gas emissions. While he admits that extreme weather events are only likely to continue, an increase in these events can be curtailed by eliminating the burning of fossil fuels.

“The impacts of climate change are no longer subtle,” Mann says. “What our findings tell us is things could get a whole lot worse if we don’t act now — if we don’t move away from our burning of fossil fuels toward renewable energy.”

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