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Thursday, March 26, 2015

Slowing ocean circulation prompts more Mann bashing from deniers at WUWT

Sou | 5:29 AM Go to the first of 62 comments. Add a comment


Update: The Rahmstorf paper is getting more important by the minute. Now there are not one, not two, but three protest articles by Anthony Watts in the space of a few hours. You'll be surprised (probably not) that what Anthony thinks refutes the study actually lends support to it. See below.

Added by Sou 6:30 am 26 March 2015



There is a new paper in Nature Climate Change by Stefan Rahmstorf and others, which is getting a lot of protest from deniers. This signifies that it is potentially an important paper. Stefan has written about it at realclimate.org.

What the research suggests is that the Atlantic Meridional Overturning Circulation (AMOC) may have slowed a lot in the late twentieth century (particularly between 1970 and 1990). This is attributed to the influx of fresh cold water, primarily from melting of the Greenland ice sheet.

The research draws upon other research. In particular (see references below):
  • several years of work described in papers by Jason Box and colleagues. They have put together reconstructions of the Greenland ice going back decades - from 1840 to 2010.
  • reconstructions of sea surface temperature based on work by Michael E Mann and co (2009).

Stefan Rahmstorf was exploring the observed cold spot in the North Atlantic, in the region where the surface ocean water turns over and drives the thermohaline circulation. The way I understand it is - when it's working well, the salty water from the tropics shifts north via surface currents and, because salt water is denser than fresh and freezes at a lower temperature, it sinks. This drives the ocean conveyor belt. If this saltier water is diluted with cold fresh water, it doesn't sink as easily and that huge ocean pump slows down.

Below is the video of the ocean circulation system, from NASA, as shown in the realclimate article:



The paper doesn't include measurements of the speed of the ocean circulation system. It is about the cold region and how there are indications that it is the coldest it's been in the past thousand years. From this it is inferred that the ocean circulation system itself is slowing. Here is a map from NOAA, which I've annotated to show the region that this research is focused upon.



That cold region near Greenland has been shown to be colder in recent years than it was in the Little Ice Age. (I don't hear deniers trumpeting this fact, oddly enough.)

The paper also refers to other published papers pointing to a decline in the AMOC in recent years. One way in which this research differs from other papers is the length of time that it considers. The method the scientists used was to construct what they called an AMOC index, "by subtracting the Northern Hemisphere mean surface temperature from that of the subpolar gyre". The subpolar gyre is the region where the cold patch is, near Greenland (it's just a region, not an oceanic circulation feature).  As stated in the paper:
We   thus   assume  that differences in surface temperature evolution between the subpolar gyre and the whole Northern Hemisphere are largely due to changes in the AMOC.

It's not really that simple. There is more to the paper than that. The authors list other lines of evidence, too. I've put some links to further reading below, if you can't access the paper itself.

The Gulf Stream and AMOC


The gulf stream system is the surface ocean current that carries warm water northward in the Atlantic, from around Florida in the eastern USA and meanders way up north. As I understand it, if the conveyor belt slows down, then this affects the gulf stream, so the warm water wouldn't travel as far.

This has been a concern for some time. For example, Wallace Broecker wrote about it in Science back in 1997. He said, referring to climate models and their inability at the time to properly simulate the ocean circulations at the proper locations:
Hence, it must be concluded that predictions made with these models regarding the response of the ocean's thermohaline circulation to the buildup of the atmosphere's greenhouse blanket could be in error. Even so, there is no reason to believe that these models are supersensitive to perturbations. It may well be just the opposite. So, until the next generation of models comes along, we must take seriously the predictions by the existing ones that a large buildup of greenhouse gases might cause the ocean's thermohaline circulation to collapse. We also must take seriously the possibility that such a collapse would have profound consequences to atmospheric operation and hence global climate. Of course, those who challenge the validity of the sizable greenhouse warmings predicted by these models will fault this result on the grounds that the warming and freshening of polar waters necessary for a thermohaline shutdown will not occur.  

The commonly held view that if the circulation collapsed it would freeze up Europe is said to be incorrect, however. See this article by Richard Seager from Lamont-Doherty Earth Observatory of Columbia University. He writes how atmospheric circulation plays a greater role than the temperature of the oceans. At best it would offset some of the greenhouse warming in that region. He says:
A slowdown of the Gulf Stream and ocean circulation in the future, induced by freshening of the waters caused by anthropogenic climate change (via melting glaciers and increased water vapor transport into high latitudes) or simply by warming, would thus introduce a modest cooling tendency. This would leave the temperature contrast across the Atlantic unchanged and not plunge Europe back into the ice age or anything like it. In fact the cooling tendency would probably be overwhelmed by the direct radiatively-driven warming by rising greenhouse gases.


Impact in the southern hemisphere


If the AMOC weakens, then the warm water from the tropics would bunch up somewhere I expect. I'll have to do some more digging to see what the impact would be elsewhere. In Rahmstorf15 there was one throwaway line that I noticed, in a section discussion the Little Ice Age (my emphasis):
There is no sign in our index that a weak AMOC caused the LIA in the Northern Hemisphere; rather the data are consistent with previous findings that the LIA reflects a response to natural volcanic and solar forcing, and if anything this surface cooling strengthened the AMOC at  least during the first part of the LIA. The fact that LIA coldness seems to have been even more pronounced in South America than in Europe further argues against a weak AMOC, as the latter would have warmed the Southern Hemisphere


Anthony Watts protests and blames Michael Mann


Anthony Watts has already written two articles protesting the study (archived here and here). Two protest articles isn't a lot by denier standards. (Remember Marcott13 and the 30 plus WUWT protest articles!) However the fact that Anthony returned from his months-long vacation to write them, and that he wrote them back to back, suggests that the paper worries him rather a lot. It's important to deniers.

It also shows that he realises that climate science deniers typically only recognise the names of a very small number of climate scientists. Anthony's protests are focused on the lead author, Stefan Rahmstorf and one of the co-authors, Michael Mann. He ignores the Greenland ice expert Jason Box and all the other co-authors.

You can ignore Anthony's second protest. He reckons that all it takes to refute a paper in Nature Climate Change is two lines in a newspaper.  No need for any research, let alone a published peer-reviewed paper or comment. Anthony relies on an article by one of his science deniers, who trumpets one short quote from another oceanographer, Martin Visbeck, at the tail end of a German newspaper article on the subject, with no supporting evidence, as proof that the research has been "debunked". The quote being (courtesy of Google translate):
The climate scientist Martin Visbeck from GEOMAR Helmholtz Centre for Ocean Research Kiel looks Rahmstorf's interpretation of the results critically: "The concentration of study on the part of the subpolar Atlantic and the spectral analysis are interesting," he says. But there were also other estimates of the AMOC, pointing to a very different course. The work does not provide strong evidence for the development of the AMOC during the past fifty years.

The gist of Anthony's first protest (which he also grandiosely calls a "debunking") is a recent paper by Tom Rossby and colleagues, which indicated there has not been a slowdown in the gulf stream over the past twenty years. However that research doesn't necessarily conflict with the Rahmstorf paper. For one thing it was using measurements from the gulf stream in the mid-north Atlantic, far from the sub-polar gyre. More particularly the observations were taken between 1992 and 2012. From the Rossby paper:
Between 1992 and 2012, we completed 20 years of operations measuring currents between the U.S. East Coast and Bermuda, spanning the outer shelf, the Slope Sea (between the continental shelf and the Gulf Stream), the Gulf Stream, and the Sargasso Sea.

Remember that the Rahmstorf paper was about a twentieth century slowdown, particularly between 1970 and 1990, before Thomas Rossby started taking measurements. The Rahmstorf paper states in the abstract:
Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. 

Tom Rossby doesn't preclude any future slowdown. In fact it's probably concern about the possibility of a slowdown in the ocean circulation that prompted his research. In the introduction he wrote, referring to earlier research including Broecker's 1997 paper (my emphasis):
In more recent years, as knowledge of ocean dynamics and modeling skills have improved, it is more widely thought that the MOC might weaken to some degree, but neither shut down nor increase in strength [Intergovernmental Panel on Climate Change Fourth Assessment Report, 2007; Yin et al., 2009]. While comforting, considerable uncertainty remains, especially given indications of increased ice melt on Greenland [e.g., Jungclaus et al., 2006], hence the need for continued and improved observation and further research [e.g., Srokosz et al., 2012]. 

I fully expect Rahmstorf15 will generate some discussion and controversy in scientific circles. I'd take notice of that and ignore the idiocy of deniers, who reject everything and anything to do with climate as a matter of course. I also expect that there will continue to be a lot of research on the subject. The big worry will be the impact of the melting of Greenland. That will need to be closely monitored.


Update - A third protest from WUWT


Anthony Watts has written a third article (archived here) protesting the Rahmstorf paper. This latest one is about a NASA study, which, like the Rossby paper, found that the AMOC showed no significant slowing between 2002 and 2009, and that it "sped up about 20 percent from 1993 to 2009".

In fact, this lends support for the Rahmstorf study, which also found that there was a recovery post-1990. Here is a chart of the "AMOC index" from Rahmstorf15 (click to enlarge):



Furthermore, Rahmstorf cites the NASA research that deluded Anthony thinks refutes the work (the 19 at the end is a reference to the NASA study) - my emphasis and h/t David Sanger:
The twentieth century shows a gradual decline in the AMOC index, followed by a sharp drop starting around 1970 with a partial recovery after 1990 (discussed further below). This recovery is consistent with the finding of an AMOC increase since 1993 based on floats and satellite altimeter data 19

BTW -- Anthony got so excited that he thought the NASA press release was new. He was much chagrined to be told by Andrew Freedman that it was from 2010!

[Added by Sou 6:30 am 26 March 2015]


From the WUWT comments


Best to ignore most of the comments. They are mostly scientist-bashing, particularly Mann-bashing (a favourite sport of the denialati), with almost no comments on the science itself. I did come across a gem that has to be shared, and not just because this paper was about ocean circulation not rising sea levels:

Curious George thinks seas cannot rise because there is a limited water supply on our planet :)
March 24, 2015 at 2:13 pm
Dr. Rahmstorf developed a model of a sea level rise, ignoring an inconvenient fact of a limited water supply on our planet.


Further reading


You can read more about this research at realclimate.org and on Jason Box's blog.  Both articles are full of links to further reading. Chris Mooney has written an article about it, too.

There's a nice blog article by Kaitlin Alexander at ClimateSight about AMOC and the gulf stream. She wrote it a couple of years ago.

There's also an easy-to-follow article about the gulf stream system at the Max Planck Institute for Meteorology website.


Rahmstorf, S., J.E. Box, G. Feulner, M.E. Mann, A. Robinson, S. Rutherford and E.J. Schaffernicht, "Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation", Nature Climate Change, 23 MARCH 2015 | DOI: 10.1038/NCLIMATE2554

Box, Jason E., and William Colgan. "Greenland ice sheet mass balance reconstruction. Part III: Marine ice loss and total mass balance (1840–2010)." Journal of Climate 26, no. 18 (2013): 6990-7002. doi: http://dx.doi.org/10.1175/JCLI-D-12-00546.1 (pdf here)

Mann, Michael E., Zhihua Zhang, Scott Rutherford, Raymond S. Bradley, Malcolm K. Hughes, Drew Shindell, Caspar Ammann, Greg Faluvegi, and Fenbiao Ni. "Global signatures and dynamical origins of the Little Ice Age and Medieval Climate Anomaly." Science 326, no. 5957 (2009): 1256-1260. DOI: 10.1126/science.1177303

Sherwood, Owen A., Moritz F. Lehmann, Carsten J. Schubert, David B. Scott, and Matthew D. McCarthy. "Nutrient regime shift in the western North Atlantic indicated by compound-specific δ15N of deep-sea gorgonian corals." Proceedings of the National Academy of Sciences 108, no. 3 (2011): 1011-1015. doi: 10.1073/pnas.1004904108 (open access)

Broecker, Wallace S. "Thermohaline circulation, the Achilles heel of our climate system: Will man-made CO2 upset the current balance?." Science 278, no. 5343 (1997): 1582-1588. DOI: 10.1126/science.278.5343.1582 (pdf here)

Rossby, T., C. N. Flagg, K. Donohue, A. Sanchez‐Franks, and J. Lillibridge. "On the long‐term stability of Gulf Stream transport based on 20 years of direct measurements." Geophysical Research Letters 41, no. 1 (2014): 114-120. DOI: 10.1002/2013GL058636

62 comments:

  1. I laughed at the Curious George comment as well when i saw it. I have been riling them up over in the second protest article. I feel like a ban is imminent...

    My opening volley was "failure to understand the subject matter is not debunking."

    ReplyDelete
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    1. Have you been subjected to an 'intervention' by their comedy attack dog dbstealey yet?

      Delete
    2. Oh yes, we "met" the other day... He is currently "disgusted by you and your ilk".

      I have also drawn the ire of .mod who promptly Godwin'd the thread.

      Delete
    3. i kinda figured it was, thanks

      Delete
    4. "I feel like a ban is imminent..."

      I've had that feeling a few times.

      Delete
    5. Follow up:

      [Reply: You seem to have a hard time following simples rules. To put it plainly, if you continue to label readers as ‘deniers’, ‘denialists’, or similar pejoratives that equate people with Holocaust deniers, you will have to find another venue to post your comments. We do not tolerate neo-Nazis here. Clear enough? ~mod.]

      That's Stealey-logic alrighty, but not quite his usual voice.

      Delete
    6. dbstealey seem to have the job of attack dog on that site. His job is to respond to any pro-global warming comment with whatever nonsense he can dream up.

      Delete
    7. It's funny how he only shows up when there's a disagreement with the article. He proceeds to convolute and distract from the original topic, ultimately devolving into his calls for my identity.

      And yes, I have a problem following simple directions haha.

      Delete
    8. It is a diversionary tactic, and also gives "the faithful" the impression that he has countered your comment. It relies on "the faithful" not actually understanding the comments, of course.

      I have seen similar behaviour in anti-vaccers, chemtrailers, Creationists, and (that strange bunch) Electric Universe supporters.

      Delete
    9. @Someone Else. I used my real name and business email address to join WUWT and my profession is specifically described in that email address.
      In or around September last year Anthony and Stealey attempted to intimidate me by posting pictures of me.

      All up 7 photographs of someone sharing my name and nationality (but not my profession) were posted.

      I have never been slow to seek legal remedies, so I wrote to Anthony that I intended to own his house and demanded that he contact (via facebook) the person he was passing off as me and apologise for maliciously and falsely dealing in his image. He shat himself and apologised both to me and the owner of the photographs. He emailed the link to the apology and then banned me and removed every trace of me from the site. He will not even allow others to refer to me so strict is that ban.

      His intimidatory conduct has no place on any blog let alone one that claims to be a science site. Watts and Stealey are peas in a pod - gutless and contemptible.

      Delete
    10. Someone else,

      DB frequently speculates about my personal details. On one particularly heated thread he divulged his height and weight and muttered something about knowing what state I live in. I told him that I'd save him the expense narrowing that down and published my full street address. Told him to stop by for a visit any time. That pretty much took care of that.

      Harry Twinotter,

      Wellll .... the universe is obviously a finite state machine. AOGCMs are just an emergent recursion ....

      Delete
    11. PG ... I begin to understand more and more.

      Delete
    12. Brandon R. Gates.

      ha ha good one. Certainly a regression to word salad at times :-)

      I saw DB and one of his tag team/sock puppets speculate on my identity. Yeah does seem to be a pattern of intimidation here.

      I know I had one clown checking my Twitter feed, he tried to make something out of my attendance at a Climate March I twittered about.

      Delete
    13. The reason I described dbstealey as a 'comedy attack dog' is that as a moderator he is supposed to detect and stop the activity he himself indulges in: insults, threats, sockpuppetry. Even if the numpties at WUWT cannot understand the science they ought to be able to understand that moderators are not supposed to behave like trolls. Its another good indication of WUWT's credibility.

      Delete
    14. You'll only very rarely see anyone come out in support of what Smokey/dbstealey writes at WUWT. I think even WUWT-ers see him as a joke (at best).

      Delete
    15. Just looked at those threads, and I just had to laugh. Dbstealy posted:

      "I have exactly one (1) screen name, which is also my real name. I do not use multiple identities. Why should I? I wear my heart on my sleeve. Everyone knows exactly where I stand. [...] It’s called ‘projection’. Now, why would you assume I am using anything but my real name? Projection, no doubt."

      This from "dbstealey", also the moderator "dbs", who also posted at WUWT as "D. Boehm" and the infamous "Smokey", often on threads where he was moderating as "dbs" and clipping/slamming anyone who disagreed with his sock puppets.

      Yes, "It's called projection.". Astounding.

      Delete
    16. Wow, sounds like I've just seen the tip of the iceberg. I think my new personal policy will be to ignore him lol. That might fire him up even more.

      I had a conversation in the FEMA thread with a guy named D.S. that used the same logic as him, he wants to arm everyone in America in order to stop violent crime.

      Delete
    17. That thread KR posted gets even funnier after the dbstealey bit KR quoted. "Someone Else" is giving dbstealey such a hard time that the ".mod" starts intervening in support of dbstealey, the guy who does not use multiple identities. No points for guessing who ".mod" is.

      https://www.youtube.com/watch?v=FgItntk5kTE

      Delete
    18. Don't forget his performance in the Hadfield debate https://youtu.be/neH50KofxL0

      Delete
  2. Visbeck is a personal hero of mine. I'm sure if you pressed him on it, he would agree that there just isn't enough observational literature on the subject. But hey, why delve into the details when you can just take what one scientist said without any context and extrapolate from there?

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    1. Yeah - from my reading of the quote, that is exactly what Visbeck meant. (I don't speak German so can only go by the Google translation.) The bulk of the newspaper article was about the study. The way the journalist wrote the quote, and then added some of their own at the end was just to add a bit of journalistic spice.

      Delete
  3. Anthony's added a third protest article (see the update above). Thing is, all his 'evidence' far from contradicting, only adds support for the Rahmstorf paper - all consistently showing a possible speeding up of the AMOC from around 1990 to around 2010, including this new paper.

    (I've added one of the figures from the paper which illustrates this.)

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  4. It's four now. He must be really scared.

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  5. This comment has been removed by the author.

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  6. From Global and Planetary Change, a new paper challenging Rossby's conclusions via multiple data sources.

    Highlights:
    • Three different data sets agree on the 2009/10 decline in AMOC and the Gulf Stream.
    • Sea level difference across Gulf Stream detects variations in AMOC.
    •Sea level is used to construct a proxy for AMOC variability for 1935–2012.
    •The weakening in AMOC after 2004 is compared to a similar decline in 1960s–1970s.

    (h/t Tal Ezer)

    ReplyDelete
    Replies
    1. Thanks. Here's a link to the Tal Ezer paper:

      http://www.ccpo.odu.edu/~tezer/PAPERS/2015_GPC_AMOC_SL.pdf

      (I haven't read it yet.)

      Delete
    2. IMO, the money quote:

      Because of the different lengths of the records and the different instrumentations used, as mentioned above, there are sometimes discrepancies between different studies of the GS which may create confusion. For example, Rossby et al. (2014) claim that the Oleander data does not provide evidence that the GS is slowing down, a claim that appears to contradict evidence from other data showing recent slowing down of the GS (Sallenger et al.,2012; Ezer, 2013; Ezer et al.,2013) and weakening AMOC (Smeed et al., 2013). However, a close examination here will show that there is no real contradiction between different data sources.

      That last little nuance leaves me to wonder if Rossby et al. (2014) is actually being "challenged". Reading down:

      Note that the conclusion of Rossby et al. (2014) about a stable Gulf Stream, with large variability and no significant trend, was based on only a portion of the Oleander line (OGS) which is affected by eddies more than by AMOC and does not address the trend during the RAPID period. The main point here is that the 3 data sets are generally consistent with each other and the apparent discrepancy in different studies one may mistakenly infer from Rossby et al. (2014) reflects the fact that the studies look at different periods and only part of the data (i.e., subsection OGS rather than the whole section).

      I've been getting the feeling that ambiguous definitions and/or terminology in the literature itself is part of the "problem". There is a real problem if my sense is correct, but there's so much here I know absolutely nothing about that I don't think I can sort it.

      Delete
    3. ... re-reading David Sanger's comment below, I see my comment here is somewhat redundant.

      Delete
    4. I appreciate the breakdown, Brandon. I'm afraid I misrepresented it above.

      Delete
    5. Glad I could help, you're welcome.

      Delete
  7. There is a new paper in Nature Climate Change by Stefan Rahmstorf and others, which is getting a lot of protest from deniers. This signifies that it is potentially an important paper.

    I likely is an important paper, but the attention of the mitigation sceptics only tells us that they do not like it. They do no know enough about science to judge whether an article is scientifically important.

    The US sceptics should not like this message, the slowing down of the ocean circulation will reduce warming for Europe and increase warming for the USA. That creates a shift in the power balance. That although America is already plagued by severe weather, while Europe has a very moderate climate.

    It is "interesting" how the headlines refer to the Rahmstorf et al. paper:

    Mann on the run – latest paper ‘dead at birth’ ...

    Michael Mann and Stefan Rahmstorf claim the Gulf Stream is slowing due to Greenland ice melt ...

    NASA refutes Mann and Rahmstorf – Finds Atlantic ‘Conveyor Belt’ Not Slowing


    The preoccupation with Michael Mann is a clear sign that WUWT is a political hate blog. The audience has been conditioned to stop thinking when they hear the name Michael Mann. A science blog would call this a Rahmstorf paper.

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    1. Or read the word "model". It's been more than a bit surreal to watch Anthony roll out evidence "refuting" this study which any other time they'd be busy bashing as nonsense. Quoting Josh Willis on ARGO was a real coup. But my award for absolutely priceless goes to this comment directed at me:

      If you want to legitimize Mann, help him produce error bars, and the rationale behind them.

      I re-posted Fig. 4 from the paper AND went and dug up Fig. 5b from MBH98. The response?

      None of those charts were from the referenced paper. Mann’s wildly creative selective use of proxy “data,” the way he spliced thermometer data onto treemometer data, and invented a new, quite baseless application of Principal Component Analysis, are well-documented. You, sir, have drunk the Kool-Aid, good luck…

      If you can't even honestly deal with the indisputable fact that the relevant works contain error bars on the pretty pictures ...

      Delete
  8. J C is now citing Anthony Watts in this matter over at CE.

    Judith Curry leaving no depths unfathomed with only 20% of air left in her tank. Will she ever make back to the surface?
    Na.

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    1. Yes I saw that. She also starts off her comments with some ad hominems and straw men.

      Delete
    2. Curry's comment, before passing the mic to Watts:

      "Well, if there is anything I distrust more than climate model simulations of decadal to millennial scale ocean circulations and internal variability, it is Mannian proxy analysis of same. It seems like strip bark bristlecones and Tiljander sediments can tell us about Gulf Stream flow rates, as well as global temperatures. Remarkable."

      She probably doesn't even remember those long-ago days when she worked at being a scientist.

      Delete
    3. I think you can classify her comments as "poisoning the well".

      Delete
  9. Here's Michael Mann specifically addressing the claims that his study is contradicted by the Rossby paper.

    https://www.facebook.com/MichaelMannScientist/posts/873222562733947

    "Some critics have tried to make hay over a previous article from last year by URI Graduate School of Oceanography scientist Tom Rossby (see: http://www.gso.uri.edu/b…/rossby-gulf-stream-is-not-slowing/) they claim contradicts our recent Nature Climate Change study finding evidence for a long-term slowdown of the Atlantic Meridional Overturning Circulation ("AMOC"). [Tom incidentally is the son of the great meteorologist Carl-Gustaf Rossby of "Rossby wave" fame: http://en.wikipedia.org/wiki/Carl-Gustaf_Rossby. He also happens to be a friend. He is one of leading physical oceanographers of our time. His scientific work is extremely thoughtful, careful, and solid].

    Rossby employs direct measurement of Gulf Stream transport using a ship-board acoustic Doppler current profiler (ADCP) over the interval 1993-2012. I have no reason at all to doubt Rossby's findings. And they do *not* conflict with our own findings (though some have misleadingly sought to assert they do) for two fundamental reasons:

    1. One man's signal is another man's noise: Over the relatively short interval (1993-2012) in question, we too find little or no net trend (!). The trends that we identify in our article are longer-term in nature, and are corroborated by independent studies and independent data (e.g. Nitrogen isotope data from corals) as documented in our article.

    2. What Rossby is measuring is largely associated with the wind-driven boundary current of the subtropical horizontal ocean gyre, the warm poleward current that hugs the coastline of the southeastern U.S., the current that *physical oceanographers* refer to as the "Gulf Stream". This is rather different from what we are looking at, which is what oceanographers instead refer to as the "AMOC" and more specifically, the "thermohaline circulation" (sometimes also called the "conveyor belt" because of the shape of the circulation cell, which in the Atlantic carries warm waters northward near the surface and cold waters southward at depth, thus providing a net transport of heat poleward). That vertical overturning circulation is driven instead by lateral density contrasts that arise due to variations in temperature and salinity. The shallow component of this ocean circulation pattern does not recirculate within the subtropical gyre and instead continues northward across the North Atlantic toward Iceland and Europe. That component is typically referred to as the "North Atlantic Drift" by oceanographers. It is not the "Gulf Stream". But the problem: in common parlance (and numerous news articles and reports), it *is* referred to as the "Gulf Stream".

    So in short, we and Rossby aren't really looking at the same current system (though one might think so due to the confusing and often inconsistent use of the "Gulf Stream" terminology), and even if we were, both studies agree that there was little or no trend over the quite short interval of 1993-2012.

    It is always useful to question new studies, and subject them to the full scientific scrutiny they deserve. And Carl Sagan's famous maxim "the more extraordinary the claim, the more extraordinary the evidence must be" certainly applies. But bad faith efforts to confuse the public by erroneously conflating two very different findings has no place in the public discourse over the science and its implications."


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    1. She is a scientist and academic yet she is comfortable in relying on AW's deceptive and malicious drivel to support her groundless attack on Mann.
      That's more than laziness..way more.

      Delete
  10. I have this recollection I read a study that the winds in the North Atlantic are also important. The warm hypersaline water from the tropics does sink somewhat before it gets to the North Atlantic. Strong winds then expose the warm hypersaline water again and allow the heat to be transferred to the atmosphere. The now-colder water sinks again and travels south.

    It stuck in my mind because it also said the "Gulf Stream" is not the same as the AMOC.

    If I can remember where I read it I will post - it may add some interesting points.

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    1. Harry, hi,

      I'm a bit upset/confused by this conflation of the AMOC (thermohaline circulation) and the Gulf Stream too, and I think the main culprit of this confusion is not the media, but actually an article by Stefan Rahmstorf (the lead author of the paper) up on Real Climate:

      http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/

      It's more like a press release, and this is the opening para (my emphasis added):

      The North Atlantic between Newfoundland and Ireland is practically the only region of the world that has defied global warming and even cooled. Last winter there even was the coldest on record – while globally it was the hottest on record. Our recent study (Rahmstorf et al. 2015) attributes this to a weakening of the Gulf Stream System, which is apparently unique in the last thousand years.

      As Mann says in the text above quoted by David Sanger, the AMOC and what is considered as the Gulf Stream by oceanographers are two separate things, but Stefan is seemingly conflating them right there on his own home page. IMO, Real Climate are shooting themselves in the foot on this one, and they should get their act together fast and try to clean up the mess!

      Unfortunately, the damage has already been done: the AGW deniers have the memory abilities of a goldfish when it comes to anything scientists get right, but when scientists get it wrong, they have the memory of an elephant. You'll still be hearing about it 30 years from now.

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    2. I do not know if there is a difference between "Gulf Stream" and "Gulf Stream System".

      My understanding is the Gulf Stream makes up part of the AMOC.

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    3. Words are not always completely unambiguous. The corresponding articles describe what they mean with it. That that differs between articles and that that may be important for the interpretation is a fact of life.

      When someone talk about the global mean temperature, you also sometimes need additional information, such as which dataset exactly was used.

      The unreasonable will always complain, there is nothing we can do against stupid comments by the mitigation sceptics by to ignore them when it comes to science.

      Delete
    4. metzomagic,

      I experienced the same dissonance and upset, more because I waded into the fray at WUWT before reading the RC thread, and lead at WUWT with an apples/oranges rebuttal. Which, as it turns out, wasn't totally wrong. From the comment thread, Dr. Rahmstorf replies to the question: http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/#sthash.lfiUQCr9.dpuf

      [Response: We are talking about the AMOC here, not the western boundary current which indeed is largely wind-driven, and more specifically about the thermohaline driven part of the AMOC. Its variations are controlled by density changes in high latitudes and not from the tropics. In paleoclimate, I would say it is well established by now that things like the Younger Dryas event or the climatic response to Heinrich events are driven by high-latitude buoyancy (mainly freshwater) forcing. Fans of the tropics as climate driver have tried but in my view failed to come up with alternative explanations for these events. -stefan]

      Does not clear up the Gulf Stream/Gulf Stream System ambiguity, but does abundantly describe the scope of his study.

      Delete
    5. Victor, Brandon, hi,

      *I* know they're talking about the AMOC up there on Real Climate, and *you* know they're talking about the AMOC (because we take the time to read the whole article), but as Victor says, deniers are gonna deny so why hand it to them on a plate?

      You know they're going to quote mine the 'Gulf Stream' bit out of the first para and have a field day with it, not bothering to read any further because they've already satisfied their confirmation bias.

      Delete
    6. metzomagic,

      Well yes, I did have a bit of "really guys?" reaction along the lines of serving one up on a gilded platter -- not for the first time -- but that's where you and Victor both make the salient point: haters gonna hate. Especially when MEM is in the the list of authors, not least because the fact he's still publishing rubs their noses in their own impotence.

      Delete
    7. Anon, thanks for the vid, that helped.

      Delete
  11. Off Topic. Looks like Roy Spencer has had his hand under the scales at Hunstsville

    ReplyDelete
    Replies
    1. Surely not deliberate.

      But if there's any impropriety, even just unconscious, it must be observed that he's not the scientist, he a very naughty Roy.

      Delete
    2. I'm sure it's not deliberate. It's quite conceivable that you could run a consistently outlying research organisation and never be curious about how that status was achieved. Deliberate or not this is going to be big.

      Delete
    3. Dang, wrong 'Reply' button. So that my previous attempt doesn't become orphaned from its context...

      I'm a little surprised that nobody's updated the Wikipedia page yet:

      http://en.wikipedia.org/wiki/UAH_satellite_temperature_dataset#Corrections_made

      I suppose that everyone's still preoccupied by the AMOC paper...

      Delete
    4. Well they're certainly not preoccupied by Toll's Cook13 rehash.
      ATTP is currently being way too polite with the guy when the kindest thing Anders could do is to counsel Richard to avoid posting comments after the cocktail hour....or is he always like that?

      Delete
    5. Deliberate. Count on it. Anyway, until proven innocent!

      Delete
  12. I'm a little surprised that nobody's updated the Wikipedia page yet:

    http://en.wikipedia.org/wiki/UAH_satellite_temperature_dataset#Corrections_made

    I suppose that everyone's still preoccupied by the AMOC paper...

    ReplyDelete
    Replies
    1. If the Po-Chedley paper helps to retire the "no tropical hotspot" meme (or the terrible twosome at UAH), humanity will owe the authors an enormous debt.

      Delete
  13. PG. That's an amazing story regarding you being falsely exposed on WUWT. It seems that their calls for people to use their real identities is just a rouse to enable them to intimidate. They really are a despicable bunch.

    ReplyDelete
  14. I haven't seen anyone mention what to me was the most hilarious aspect of Watts's first (?) post on the AMOC paper.

    In his haste to find as many faults as possible, he claimed that Greenland is gaining mass, not losing it. He did this by completely ignoring the past two decades' worth of actual data, measurements, observations ... and focused only on one single year's output from a climate model.

    Yes, the figures he included come from DMI, where, if you follow the links, you'll see that they basically are just running a climate model and predicting the surface mass balance (precip minus runoff, basically). There's no inclusion of discharge (ice mass lost from calving glaciers) of course, but the funny part is that the SMB data are purely 100% climate model output.

    So Anthony is rejecting actual observations in favor of climate model outputs. Go figure.

    ReplyDelete
    Replies
    1. Today's lead article at WUWT: Study: Climate change does not cause extreme winters

      Text of the press release: Using a highly simplified climate model, they examined various climate scenarios to verify their theory.

      My only possible response: Dear me, the only worse thing they could have done is used tree rings.

      Dealing with the dissonance 101: Are you auditioning for a job as village idiot?

      Dealing with the dissonance 201: Taken.

      Dealing with the dissonance PhD dissertation: It all stands or falls together, Brandon. Either climate models are reliable, and you have to accept that there will be no increase in extreme weather, or they are unreliable, and you will have to concede there is no basis for any type of alarm over increasing atmospheric CO2. So, which is it?

      Conclusion: We really are heading for an ice age ... due to global dimming.

      Delete

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