Climate-addled jet streams boost drought, flood: study

March 27, 2017 by Marlowe Hood

Global warming amplifies severe droughts and floods by disrupting jet streams, the powerful high-altitude air currents that move west-to-east across the northern hemisphere, researchers said Monday.

Just in the last 15 years, devastating drought in California, heat waves across the United States and western Europe, deadly flooding in Pakistan—all were made worse when manmade climate change altered these massive airstreams, they reported in the journal Scientific Reports.

"Our work shows that climate change isn't just leading to more through the usual mechanisms," said lead author Michael Mann, a professor at Penn State University in the United States.

These "usual mechanisms" include warmer temperatures leading to more and droughts, and additional moisture in the air leading to more flooding or snowfall.

"In addition to these effects, is changing the behaviour of the jet stream in a way that favours more extreme and persistent weather anomalies," Mann told AFP.

"We have uncovered a clear fingerprint of human activity."

Jet streams are ribbon-like currents of air that snake across the northern half of the globe about 8 to 11 kilometres (five-to-seven miles) above Earth's surface.

Driven by the contrast between frigid polar air and tropical climes, jet streams travel in a band several hundred kilometres wide at speeds of up to 300 kilometres (about 200 miles) per hour.

Jet streams are the reason it takes an hour less to fly from Los Angeles to New York than the other way around.

The meandering path of these giant air flows creates weather patterns, including the low- and high-pressure systems that create unseasonable cold or hot spells.

Connecting the dots

When jet streams slow or stall, these weather systems can become more extreme, leading to extended periods of heat or precipitation.

"Relatively small changes to the jet stream can have a large effect on weather and extreme weather," co-author Dim Coumou, a professor at the Institute for Environment Studies and VU University Amsterdam, told AFP.

And what causes these massive air flows to stall? It is a smaller temperature difference between the Arctic and tropical air that corrals them on either side.

That can happen naturally, but has occurred even more frequently as has set in, the researchers found.

The Arctic has warmed more than twice as fast over the last half-century as the global average, rising by two degrees Celsius (3.6 degrees Fahrenheit).

Air over land masses has also heated up more quickly than over the oceans.

Earlier research linked with major drought and floods over the last two decades, but said nothing about whether human activity helped drive the process.

"What the new study does is connect the dots between the increased frequency of this jet stream effect and human-caused warming on the planet," Mann said.

Mann and his team used surface temperature records reaching back to 1870, combined with computer models, to look for patterns.

It turned out that conditions favouring the stalling of the jet stream have increased by about 70 percent since the beginning of the industrial age, when humans began loading the atmosphere with heat-trapping greenhouse gases.

Significantly, most of the change has occurred in the last four decades.

"The more frequent and persistent meandering jet stream states seem to be a relatively recent phenomenon," said Coumou.

The 196-nation Paris climate pact calls for holding global warming to "well below" 2 C.

On current trends, Earth's surface is on track to heat up by about 4 C (7.2 F).

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14 comments

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rhugh1066
2.3 / 5 (12) Mar 27, 2017
I wonder why no positive effects of global warming are ever discovered? It seems counter-intuitive that nothing is ever found.
cjones1
3 / 5 (8) Mar 27, 2017
Can they explain the "Dust Bowl" drought or the earlier droughts that are attributed to the demise of Native American cultures such as the Anastazi? That the Jet Stream and decadal oscillating atmospheric currents contribute to drought and flood events is a no brainer.
cantdrive85
1.7 / 5 (11) Mar 27, 2017
Note the moronic authors of this article use a contrail/chemtrail image as their "jetstream". Pathetic journalism!
Climate-addled jet streams

Here is an example of climate scientists putting the cart in front of the horse to "prove" their politically motivated "science study".
antigoracle
1.7 / 5 (11) Mar 27, 2017
The only thing that's boosted by climate change is the complete and utter bullshit from the AGW Cult.
DrHow
4.2 / 5 (5) Mar 27, 2017
The photo is irrelevant, and the caption on it is utter nonsense. Editors for what is claimed to be scientific journalism should be required to understand the science or, at least, consult someone who does.
EarthlingToo
1.4 / 5 (10) Mar 27, 2017
@DrHow: At least we know that fake news doesn't only exist in mainstream journalism, but scientific journalism too.
gkam
4 / 5 (12) Mar 27, 2017
I do not consider Fox News to be " mainstream journalism".
MR166
1 / 5 (7) Mar 27, 2017
"I do not consider Fox News to be " mainstream journalism"."

Wow Gkam what an earth shattering statement. I fully expect Fox viewership to plummet when this news reaches the public.
MR166
1 / 5 (8) Mar 27, 2017
All of these so called "scientific" news releases have been timed to coincide with Earth Day. The Ministry of Propaganda must have been working all week to prepare for this.
cantdrive85
1.7 / 5 (6) Mar 27, 2017
The photo is irrelevant, and the caption on it is utter nonsense. Editors for what is claimed to be scientific journalism should be required to understand the science or, at least, consult someone who does.

Note: 6 hours later the caption is gone and all that remains is the irrelevant image.
ddaye
5 / 5 (4) Mar 27, 2017
All of these so called "scientific" news releases have been timed to coincide with Earth Day.

Earth day was a month ago.
lupus
1 / 5 (1) Mar 28, 2017
"jet streams, the powerful high-altitude air currents that move west-to-east across the northern hemisphere"

So what do they have in the southern hemisphere ?

Did someone get paid for writing this ?

MR166
1 / 5 (5) Mar 28, 2017
"http://www.dailym...ur.html"

You are right it was not earth day. It was some other green BS.
Captain Stumpy
3 / 5 (2) Mar 30, 2017
@nazi-sympathizing eu pseudoscience troll
Here is an example of climate scientists putting the cart in front of the horse to "prove" their politically motivated "science study"
actually, no
this is an example of an article presenting Marlowe Hood's interpretation of science

the science comes from this: http://www.nature...rep45242

if you will note that it also uses references i've tried to get you and others to read, like Francis,Vavrus et al

Francis,Vavrus have also been validated through multiple sources

so this is the accumulation of validated and other studies that demonstrate what is considered to be good science

.

All of these so called "scientific" news releases have been timed to coincide with
@mr
and if you read the science rather than your biased news sources you would know that Climate Science gets published year round - not just during "green" movements

so there goes your propaganda theory, mr conspiracy
foil hat time for ya

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