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ChrisReynolds

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Francis/Vavrus paper flawed.
« on: October 01, 2013, 08:59:00 PM »
I've just come across research that shows that the Francis/Vavrus paper on larger meanders and slowing of the Jetstream is in doubt.


Barnes 2013, Revisiting the evidence linking Arctic Amplification to extreme weather in midlatitudes.
http://barnes.atmos.colostate.edu/FILES/MANUSCRIPTS/Barnes_2013_GRL_wfigs_wsupp.pdf
Quote
Previous studies have suggested that Arctic Amplification has caused planetary-scale waves to elongate meridionally and slow-down, resulting in more frequent blocking patterns and extreme weather. Here, trends in the meridional extent of atmospheric waves over North America and the North Atlantic are investigated in three reanalyses, and it is demonstrated that previously reported positive trends are an artifact of the methodology. No significant decrease in planetary-scale wave phase speeds are found except in OND, but this trend is sensitive to the analysis parameters. Moreover, the frequency of blocking occurrence exhibits no significant increase in any season in any of the three reanalyses, further supporting the lack of trends in wave speed and meridional extent. This work highlights that observed trends in midlatitude weather patterns are complex and likely not simply understood in terms of Arctic Amplification alone.

To quote from my recent blog post:
The Francis/Vavrus paper linking Arctic Amplification to increased amplitude of waves in the Jetstream and 'stuck' weather patterns is now looking like it is wrong. In the Barnes paper it is noted that "metrics that focus on a narrow range of isopleths to track the ridges and troughs of a passing wave will incorrectly interpret a shift of the geopotential height field as a change in wave extent. When this shift is accounted for, no significant trend is found."

 In other words, with the warming of the northern hemisphere the atmosphere has been expanding, shifting geopotential heights upwards (geopotential height being the height at which a certain pressure level is found). And causing a northward shift of geopotential height. Barnes attacks the problem in a very intelligent way, she defines two indices, SeaMaxMin is the seasonal excursion of peaks and troughs in the 500mb GPH field, where GPH is 5700m up in the atmosphere, DayMaxMin is the same index but on a daily basis. In line with Francis and Vavrus SeaMaxMin has an upward trend, but crucially DayMaxMin doesn't. This is fatal problem for the Francis/Vavrus paper, because if their hypothesis is correct both indices should show an upwards trend.

EDIT - I've changed the first line to say the paper is flawed.
Discussion at my blog with Kevin O'Neill has tempered my conclusion, the blog post and comments are here:
http://dosbat.blogspot.co.uk/2013/10/francisvavrus-and-slower-jetstream.html
« Last Edit: October 03, 2013, 06:47:36 PM by ChrisReynolds »

JimD

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Re: Francis/Vavrus paper flawed.
« Reply #1 on: October 01, 2013, 09:39:26 PM »
Thanks Chris, that is very interesting.
We do not err because truth is difficult to see. It is visible at a glance. We err because this is more comfortable. Alexander Solzhenitsyn

How is it conceivable that all our technological progress - our very civilization - is like the axe in the hand of the pathological criminal? Albert Einstein

werther

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Re: Francis/Vavrus paper flawed.
« Reply #2 on: October 02, 2013, 08:06:48 AM »
Thanks for introducing us on this paper, Chris!

It is always tempting to accept a vision as a clear mark on the way to complete understanding. But most phenomena are too complex to fit into one general scheme.

After having noodled myself with the NCEP/NCAR mappings last winter, I haven’t cleared much on this matter too. Just the gradual, small trend of rising GPH stuck to me. But it is all going in small steps and reacting to many regional circumstances.

As it happens, I took this September graph from NCEP/NCAR:



I can’t get to the corresponding GPH 500Mb anymore, because the bipartisan stand-off in the USA has shut down some of our wonderful sources of information too.

But obviously, the large, anomalously warm body of open water around the Barentsz Sea is having a strong influence on the regional atmospheric behaviour.

I put it here to suggest that there are consequences that stand out against the climate mean and seem to fit with the Francis/Vavrus theory. But, as Barnes shows, there’s more to it than that…

werther

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Re: Francis/Vavrus paper flawed.
« Reply #3 on: October 02, 2013, 09:32:07 AM »
I’m digesting the line on the shut down of NOAA in my post above…

It looks like, in the slipstream of bashing health care reform in the USA, the extremist conservatives are successfull in replacing science with creed irrationality too…

ritter

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Re: Francis/Vavrus paper flawed.
« Reply #4 on: October 02, 2013, 05:26:46 PM »
I’m digesting the line on the shut down of NOAA in my post above…

It looks like, in the slipstream of bashing health care reform in the USA, the extremist conservatives are successfull in replacing science with creed irrationality too…

Totally off topic, but since you brought it up.... Incredible stupidity being displayed by my government. Petty schoolyard bickering has put 800,000 out of a paycheck for who knows how long. They should be embarrassed. My 10 year old displays more compassion, diligence and attention to duties.

No way will this bag of offal-spewing buffoons ever do anything meaningful to rectify our climate situation.   >:(

ChrisReynolds

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Re: Francis/Vavrus paper flawed.
« Reply #5 on: October 02, 2013, 07:21:11 PM »
No way will this bag of offal-spewing buffoons ever do anything meaningful to rectify our climate situation.   >:(

My previous blog post deviated towards that conclusion, and the buffoons I'm referring to are most of humanity. With respect to Congress - some idiot has to vote the idiots in.

Jim, thanks.

Werther,

It's worth considering where this leaves us. Cohen's work on snow line advance and severe winters remains sound. As does Petoukhov & Semenov's work on Bering Sea low ice leading to cold central western European winters. And my personal hobby horse of cool wet UK summers post 2007 (2013 being an exception) isn't affected. I googled the title of the Barnes paper and just found denialists getting the wrong end of the stick - we are still firmly in the realm of Arctic sea ice impacts. The only thing this changes is that there is now little evidence of a strong impact across the US - which for US denialists is of course the whole world!

For the US Cohen's work applies, although Kosaka and Xie seem to attribute some of the cold weather pattern to ENSO, likewise in Europe, but IIRC the statistical certainty is low for ENSO influence in both regions. So my working assumption is the Cohen mechanism is the primary one. Petoukhov & Semenov still accounts for the Feb 2012 cold outbreak over Europe. The summer pattern implies low pressure anomalies over Siberia forming an Arctic dipole - still sound IMO, it also implies a low anomaly across much of the northern US, but this seems too small to be significant.

Anyway, the UK seems to be taking a hit from Arctic sea ice loss in both summer and winter at this early stage of the game, which is only fair because we started the whole fossil fuel based industrial revolution.  ;D

JackTaylor

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Re: Francis/Vavrus paper flawed.
« Reply #6 on: October 03, 2013, 05:05:49 PM »
I'm Off-Topic Again:
No way will this bag of offal-spewing buffoons ever do anything meaningful to rectify our climate situation.   >:(
Unfortunate that is the way it is. 
However, how long will we have to endure until something happens which causes demands from so-called right-wing constituents of these offal-spewing buffoons to do something about AGW?

IMHO, November 2020 - one mid-term election and one presidential election after Obama...
Have mercy on me in 2014, 2016, & 2018.

Jim Hunt

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Re: Francis/Vavrus paper flawed.
« Reply #7 on: October 03, 2013, 05:59:43 PM »
Chris,

Some related research from my friendly local neighbourhood University:

http://emps.exeter.ac.uk/mathematics/staff/js546/publications

You will note some of it is open access. As is this also.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

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Re: Francis/Vavrus paper flawed.
« Reply #8 on: October 03, 2013, 06:32:39 PM »

Anyway, the UK seems to be taking a hit from Arctic sea ice loss in both summer and winter at this early stage of the game, which is only fair because we started the whole fossil fuel based industrial revolution.  ;D

And given that UK cuisine is some of the worst on the planet, there will be little suffering from the loss of the Brits. ;D

ChrisReynolds

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Re: Francis/Vavrus paper flawed.
« Reply #9 on: October 03, 2013, 07:06:48 PM »
Following discussion at my blog and consideration today I have tempered my appraisal and think the Francis/Vavrus 2012 is flawed, not wrong.
My Blog post is here:
http://dosbat.blogspot.co.uk/2013/10/francisvavrus-and-slower-jetstream.html


Thanks Jim,

There's a link to the Screen/Simmonds paper "Exploring links between Arctic amplification and mid-latitude weather" on that page - via a 'handler' page. There's also mention of a paper "Caution needed when linking weather extremes to amplified planetary waves," which is related.

SH,

I like British food. Chinese? Indian? French? You won't catch me eating that foreign muck.  :P

Jim Hunt

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Re: Francis/Vavrus paper flawed.
« Reply #10 on: October 04, 2013, 12:00:41 AM »
Whether caused by a sluggish jetstream or not, the floods are coming back to South Devon:

http://econnexus.org/floods-return-to-south-west-england/

I was, however, born in Yorkshire. I cannot recommend both Yorkshire pudding and black pudding highly enough!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Richard Rathbone

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Re: Francis/Vavrus paper flawed.
« Reply #11 on: October 04, 2013, 04:59:29 AM »
Following discussion at my blog and consideration today I have tempered my appraisal and think the Francis/Vavrus 2012 is flawed, not wrong.
My Blog post is here:
http://dosbat.blogspot.co.uk/2013/10/francisvavrus-and-slower-jetstream.html


Thanks Jim,

There's a link to the Screen/Simmonds paper "Exploring links between Arctic amplification and mid-latitude weather" on that page - via a 'handler' page. There's also mention of a paper "Caution needed when linking weather extremes to amplified planetary waves," which is related.

SH,

I like British food. Chinese? Indian? French? You won't catch me eating that foreign muck.  :P

In your blog you mention a Francis response in the Wall Street Journal, but the link in the comments is to the Washington Post. I found her WP response unconvincing. A cherry picker attempting to defend her picks against someone who has called her on it. Saying that a 15 year span provides better evidence than a 30 year span is the sort of thing that WUWT does with the surface temperature record. However that's Figure 2, and I reckon that all Figure 2 does is confirm that if there really is something significant going on, they are using the wrong metric to try and capture it. Someone that really understands the atmospheric dynamics ought to be able to come up with a better metric. If that really is the best metric, then nothing much has actually changed. However, my guess is still on the side of that something is happening and with a better metric it could be demonstrated.

I reckon Figure 3 is the really damning one and Francis' response is inadequate. It doesn't support her in the slightest. It completely demolishes her position. If Francis' reasoning were correct, there should be a left-right shift in Figure 3. There is actually an up-down shift. Even if Barnes' choice of region is done to make FV12 look bad, and it wouldn't look as bad with a different choice of region, it doesn't remove the existence of the flaw in the FV12 methodology. Its capable of coming up with opposite trends depending on minor changes in the choice of isopleth used for analysis. Arguing about how tasty the cherry is, which is what Francis seems to be doing in the WP, isn't a good defense against your methodology being called out for cherry picking.

ChrisReynolds

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Re: Francis/Vavrus paper flawed.
« Reply #12 on: October 04, 2013, 07:52:33 AM »
Richard,

You're quite right, I hadn't placed as much weight as I should have on figure 3. And you may be right with regards Dr Francis's response, i.e. I have sympathy with your statement. However change in the Arctic has been more rapid lately so preferring a later shorter period has some reasoning behind it.

WSJ / WP it's all the same to me, I also assume anyone from the US knows my 'proverbial' friend in Nebrasca.  ;)

I'll correct that in the blog. Thanks.

idunno

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Re: Francis/Vavrus paper flawed.
« Reply #13 on: October 14, 2013, 10:32:23 AM »
I have read neither, but this newish paper from Peings and Magnusdottir may be of interest to others;

http://climatechangepsychology.blogspot.fr/2013/09/response-of-wintertime-northern.html

Susan Anderson

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Re: Francis/Vavrus paper flawed.
« Reply #14 on: June 01, 2015, 05:27:18 PM »
I'm not opting to start a new post, but am puzzled by the continuing argument on this. Scientists do like to pick at each other (similar to progressives preferring to argue with each other in a "circular firing squad" rather than engage with an intransigeant and determinedly ignorant and emotionally charged opposition). Surely this is a both/and. Anyway, here's an update:

http://www.carbonbrief.org/blog/2015/01/scientists-discuss-how-strongly-a-warming-arctic-is-implicated-in-extreme-weather/

Publication:
http://onlinelibrary.wiley.com/doi/10.1029/2012GL051000/abstract

Being in the northeast US and addicted to water vapor animations, I've been watching and experiencing this in real time, but "I'm not a scientist" (in the better sense) and am open to correction.

Susan Anderson

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Re: Francis/Vavrus paper flawed.
« Reply #15 on: June 01, 2015, 05:34:27 PM »
Sigh, linked to the older paper (Carbon Brief was OK).  Here's the new one:
http://iopscience.iop.org/1748-9326/10/1/014005/article

"New metrics and evidence are presented that support a linkage between rapid Arctic warming, relative to Northern hemisphere mid-latitudes, and more frequent high-amplitude (wavy) jet-stream configurations that favor persistent weather patterns. We find robust relationships among seasonal and regional patterns of weaker poleward thickness gradients, weaker zonal upper-level winds, and a more meridional flow direction. These results suggest that as the Arctic continues to warm faster than elsewhere in response to rising greenhouse-gas concentrations, the frequency of extreme weather events caused by persistent jet-stream patterns will increase."

"Wavier" is a little unscientific sounding.