Ag Weather Forum

Global Warming and Heavy Fall Rains

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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The speed and waviness of the Northern Hemisphere jet stream is affected by the temperature difference between the Arctic and the mid-latitudes. (NASA graphic)

As producers continue dealing with the impact of record-breaking rain during this fall season of 2018, a new study finds that greenhouse gases are increasingly disrupting the jet stream, the powerful river of winds that steers weather systems in the Northern Hemisphere

The results of that disruption are more frequent summer droughts, floods and wildfires. And, in agriculture, this includes extensive crop and livestock damage because of long-lasting extreme weather occurrences. The study was done by an international group of scientists, led by Penn State climate scientist Michael Mann.

This idea is not new to either the scientific community or to DTN subscribers. Back in April 2014, I wrote an article about Jennifer Francis of Rutgers University, who has done several projects tying the loss of Arctic sea ice to inconsistent jet stream patterns -- work that has been called the "Holy Grail" in understanding climate-change impact.

In this latest study, the research group noted that, on a very basic level, unusual warmth in the Arctic causes jet streams -- the rivers of air in the atmosphere that push and pull our weather around -- to slow down, stall or meander in strange ways. When the undulations of the jet stream lock in place, weather systems can be trapped and cause havoc in our weather. This development of extreme and unusual jet stream patterns is known technically as "quasi-resonant amplification."

The study finds that this occurrence could increase by as much as 50% by 2100.

For real-world examples of the adverse and damaging impact of the quasi-resonant amplification (QRA) just from this past year, the following events were cited in articles from USA Today and Inside Climate News: Blazing temperatures and wildfire conditions to California; flooding over the Eastern U.S.; unprecedented heat to the Scandinavian Arctic region; and a six-month heat wave and drought across parts of Central Europe.

To that, I would add the record-breaking rain and flooding in the spring of 2018 in the northern Midwest and the return of heavy, harvest-damaging rain in the fall of 2018 in the same region.

The mechanism for this waviness in the jet stream is due to the fact that Arctic warming has raced ahead of the global average. As those Arctic temperatures have soared, the temperature contrasts that drive the jet stream are reduced, and the river of wind more frequently twists into sharp and slow-moving or stationary waves.

Daniel Swain, a climate researcher at UCLA and the National Centers for Atmospheric Research, was not involved in the study, but nonetheless supports its conclusion about the impact of Arctic warming on the jet stream. "When the jet stream enters this wavy state, extreme weather tends to occur on either side of the amplified ridges and troughs as the storm track becomes locked in place," Swain said. He was quoted in an Inside Climate News article on this jet stream research.

The study was conducted under the auspices of World Climate Research Programme's Working Group on Coupled Modelling. The study was published in the journal "Science Advances": http://advances.sciencemag.org/…

The USA Today article on this project is here: https://www.usatoday.com/…

The Inside Climate News article is here: https://insideclimatenews.org/…

Bryce Anderson can be reached at bryce.anderson@dtn.com

Follow him on Twitter @BAndersonDTN

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Meral Martin
11/6/2018 | 11:14 PM CST
Do not believe that the farmer -readers are catching the significance of this story. Believe ag is going to be in a tough spot - or already there
Bryce Anderson
11/6/2018 | 2:00 PM CST
Thanks for taking the time to read and comment.
Meral Martin
11/6/2018 | 7:21 AM CST
The puzzle pieces are fitting together better -- thanks for the interesting read----how to adapt to this??? WHEN is energy policy going to wake up...? It appears when it already too late .