When Jennifer Francis and others advanced the idea that arctic ice losses could be impacting extreme weather patterns in the temperate zone, it was considered cutting edge, or even fringe science.
7 years later, a steady drumbeat of observations and studies have strengthened the science, which is now, if not yet “pound on the table we’re done”, as Richard Alley says, but, very much in the mainstream discussion.
Last summer’s extreme weather was a showcase of how global warming is altering our atmosphere, from a scorching heat wave that contributed to a spate of wildfires in Scandinavia and California to devastating floods and all-time record-high temperatures set around the Northern Hemisphere.
What’s new: A new study, published last week in the journal Science Advances, ties these events and other summertime extremes to human-caused climate change via an increase in a specific jet stream phenomenon, lead author Michael Mann of Penn State tells Axios.
Details: Daniel Swain, a climate scientist at UCLA who was not involved in the new research, explains the phenomenon — known as quasi-resonant amplification, or QRA — this way: “Quasi-resonant amplification refers to a condition where high-altitude winds across the Northern Hemisphere enter a spatial configuration favorable for the development and persistence of big loops in the jet stream,” he says.
- That extra-wavy jet stream can cause extreme events, such as heat waves and flooding rains, to occur on either side of the jet stream’s “ridges” and “troughs,” particularly when such patterns get locked in place.
What they did: The authors devised an indirect method of detecting changes in QRA events by examining the differences in temperature across the Northern Hemisphere and how it changes from north to south worldwide.
- The researchers also simulated the recent and future climate using numerous computer models to project how such jet stream patterns might change.
What they found: An uptick in such QRA events can, in part, be tied to rapid Arctic climate change.
- The Arctic is warming at about twice the rate of the rest of the planet, altering the temperature contrast between the equator and the pole. This gradient is a large part of what drives the jet stream.
- Overall, the jet stream phenomena tied to prolonged, severe weather extremes are likely to increase in frequency by about 50% during this century if current emissions trends continue.
- Some models show a tripling in QRA frequency.
The new study also found an unexpected result: Cutting aerosol pollution (tiny particles in the air from burning coal, for example) may prevent the jet stream from getting hung up as frequently in the future.
- Cleaning up aerosols quickly, such as by cutting power plant pollution in China and India, could lead to fewer QRA events during part of the 21st century.
- Mann cautioned that the computer models showed considerable uncertainty around this finding, though.
What they’re saying: Jennifer Francis, a scientist at Woods Hole Research Center who was not involved in the new research, told Axios the study adds valuable new information.
“I think they’re onto an important mechanism that helps explain the influences of a rapidly warming Arctic on summer weather extremes over midlatitude continents. … The underlying drumbeat in both seasons is about persistent patterns and conditions that can turn into extreme events; in summer, this means heatwaves, floods and drought.”
Quasi-resonant amplification?—-sounds like rocket science. But it’s not—just watch the cute blonde weather girls on TV as they wave their arms over the map and show you what’s happening. (And ask Jason Box where we’re going IF QRA continues and intensifies).