Gulf Stream System at its weakest in over a millennium - and an interesting debate

An interesting and timely article. They haven't been able to trace back Gulf stream activity far back enough to get a clear picture of the current changes, but this study breaks new ground and suggests that the Gulf stream system has been weakening. We don't fully know why yet, but it is believed to stem from changes in ocean circulatory patterns in relation to global warming.

This is interesting timing, given Jack's recent post here: see the last 'blog post' and comments, which suggest that the Gulf stream system is not weakening, based on a new analysis.

http://www.politicalforum.com/index.php?threads/climate-models-shown-inaccurate-again.583578/page-2

So which science study is correct? The article in Jack's favourite climate change scepticism blog is based on a legitimate science study, (albeit with conclusions contorted and reinterpreted to suit their agenda). However, the underlining science in the primary research paper is valid. We can say this with confidence as it was peer reviewed, as was the primary study on which this thread is based (see Nature publication at the bottom of this post).

How science works is that you don't really have one body of discovery negating another. That's called politics. Scientific formulation is instead a slow process of acretion, of building theories layer by layer, testing them, refining them etc. You then have a kind of a meta-analysis with probable outcomes, for example, a very public one in formulating the IPCC report. So it will be interesting to see how these recent studies will be incorporated into ongoing climate change theory.

Spoiler

[It'll also be interesting if, true to their proclivities, whether any skeptics that post here will drop in a link to blog to 'negate' this thread, and expect others to read their stuff, rather than comment on this one or engage in any meaningful discussion].

____________________________________
Body of article:

02/25/2021 - Never before in over 1000 years the Atlantic Meridional Overturning Circulation (AMOC), also known as Gulf Stream System, has been as weak as in the last decades. This is the result of a new study by scientists from Ireland, Britain and Germany. The researchers compiled so-called proxy data – taken mainly from natural archives like ocean sediments or ice cores – reaching back many hundreds of years to reconstruct the flow history of the AMOC. They found consistent evidence that its slowdown in the 20th century is unprecedented in the past millennium – it is likely linked to human-caused climate change. The giant ocean circulation is relevant for weather patterns in Europe and regional sea-levels in the US; its slowdown is also associated with an observed ‘cold blob’ in the northern Atlantic.


https://www.pik-potsdam.de/en/news/...am-system-at-its-weakest-in-over-a-millennium

Primary science article here: unfortunately it's behind a paywall, but I do have institutional access - if anyone is really interested pm me.

https://www.nature.com/articles/s41561-021-00699-z

Abstract:

The Atlantic Meridional Overturning Circulation (AMOC)—one of Earth’s major ocean circulation systems—redistributes heat on our planet and has a major impact on climate. Here, we compare a variety of published proxy records to reconstruct the evolution of the AMOC since about AD 400. A fairly consistent picture of the AMOC emerges: after a long and relatively stable period, there was an initial weakening starting in the nineteenth century, followed by a second, more rapid, decline in the mid-twentieth century, leading to the weakest state of the AMOC occurring in recent decades.

 

Ah yes, from PIK. "Propaganda is King."

 

Multiple papers excerpted and linked here:

Yet Another Model-Based Claim Of Anthropogenic Climate Forcing Collapses
By Kenneth Richard on 25. February 2021

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High-resolution climate models have projected a “decline of the Atlantic Meridional Overturning Circulation (AMOC) under the influence of anthropogenic warming” for decades (Lobelle et al., 2020). New research that assesses changes in the deeper layers of the ocean (instead of “ignoring” these layers like past models have) shows instead that the AMOC hasn’t declined for over 30 years. . . .

 

Lol. Click the spoiler in opening thread.

This is the third thread that you link the same blog post. Again, like all your other posts, no analysis of the article cited in the thread, or acknowledgement of the prestigious journey Nature that published the primary study.

You're clearly not interested in any kind of debate and based on your behaviour so far, you only exhibit an exclusive interest in the tiny fraction of studies that kinda-sorta support your claim, without an actual understanding at all of how science works: absolutely zero apparent interest in any other studies in the field, including studies by the same authors and in the same journals upon which you put such enormous weight! I am beginning to seriously doubt that you've even read the primary articles that your bloggist quotes.

I know thinking for yourself and articulating a point is hard. Believe me, I know myself how much work it is. Much easier just to copy and paste and spam blogger material than modestly read one of the articles upon which they are purportedly based, demonstrate some kind of understanding and insight and consider how it informs any other findings in the field within which it is contained.

 

There is no need for me to manually retype that which has already been well presented. As for thinking for myself, I began that process long ago, and I have faith in my own judgment. And btw, I'm not the topic.

 

A slowing of ocean currents has been hypothesized for years now. It means colder Great Britain and Scandinavia.

 

The study is predicated on the assumption that the novel proxy measures accurately predict gulf stream activity. I don't know that there is a way to conclude that it does or does not given how relatively new the science is.

 

New Findings Contradict Alarmist Rahmstorf: Arctic/Greenland Ice Melt “Barely Impacting AMOC”
By P Gosselin on 12. May 2019

Gulfstream “barely impacted” by Arctic ice melt By Die kalte Sonne (German text translated/edited by P Gosselin) Arctic ice melt barely impacting AMOC. Day After Tomorrow scenario remains fantasy, new study suggests. Figure: R. Curry, http://editors.eol.org/eoearth/wiki/File:OCP07_Fig-6.jpg; CC BY 3.0 Stefan Rahmstorf never tires of claiming the Gulf Stream system (AMOC, Atlantic Meridional Overturning Circulation) is […]

 

Dead At Birth! German Warmist Scientists Slap Down Rahmstorf/Mann AMOC Paper: “Offers No Strong Indication”
By P Gosselin on 24. March 2015

The Potsdam Institute for Climate Impact Research has been loudly trumpeting its latest paper on Atlantic ocean overturning circulation today, claiming there’s been an “exceptional twentieth-century slowdown“. The authors, who include Stefan Rahmstorf and Michael E. Mann, even suggest that the “possible cause of the weakening is climate change“. Some sites, like Climate Central here, have […]

 

Multiple Recent Papers Dispel Gulf Stream Collapse, Alarming The Climate Alarmism Industry

By P Gosselin on 10. June 2019

No Reason For Panic: The Oscillating Gulf Stream By Die kalte Sonne (German text translated/edited by P Gosselin) Image: NASA JPL (public domain) The Gulf Stream provides heating for Western Europe. Some climate activists paint horror scenarios on the wall that the Gulf Stream is slowing down or even stopping due to climate change – […]

 

1. Evidence Mounts Against Climate Prediction That Inspired ‘Day After Tomorrow’ Disaster Flick
   circulation (AMOC). The study found the Nordic Sea east of Greenland played a dominant role in the AMOC. ... Lozier led an international effort to measure AMOC in the North Atlantic. Scientists from 16 organizations
   
   
2. Study: There is no real evidence for a diminishing trend of the Atlantic Meridional Overturning Circulation
   reduction in the AMOC over the 20th century and especially after 1970. They believe the AMOC weakness after ... far for the AMOC has indices that may or may not represent the long term trend in the AMOC depurated of

 

Scientists Acknowledge Ocean Currents Not Slowing
Ocean currents March 18, 20201
Scientists are admitting ocean currents have been speeding up in recent years, dealing a stunning blow to ‘consensus’ climate science claims. For the past...

 

They were not, to my knowledge, saying the Gulf Stream was collapsing, just slowing. If winters in Great Britain and Scandinavia get colder? Evidence supporting ?

 

Excerpted from the link in #3:

Those who favor an anthropogenic explanation for these rather inconvenient cooling trends have leaned on the climate models that say the ocean’s dominant heat transport mechanism – the AMOC – has been declining in response to anthropogenic greenhouse gas forcing.

But now a new study (Worthington et al., 2021) throws cold water on this claim too.



Image Source: Worthington et al., 2021
Reconstructing over 30 years of AMOC variability (1981-2016), the authors use a “higher-fidelity empirical model of AMOC variability” that, unlike past assessments, does not “ignore changes in the deep circulation”.

The authors do indeed find there was a brief dip in the AMOC from 2004-2012. But even this temporary decline was dominated by internal variability rather than being associated with anthropogenic forcing.

In fact, Worthington and colleagues have determined that there has been “no overall AMOC decline” since monitoring began in 1981. This contradicts the results of high-resolution climate models.



Image Source: Worthington et al., 2021
Consequently, the cooling in the North Atlantic can no longer be dismissed as a response to an anthropogenically-weakened AMOC.

Something else is driving the cooling.

 

And yet you lack the capacity to have any kind of meaningful dialogue or express an opinion in your own words. The type of ignorance about how science works and attitudes contained within your blog material are relevant to the climate change debate, albeit increasingly less so. Being a sceptic and a serial spammer your behaviour is part of the topic.

I'm just disappointed. With some reservation I try to welcome the other side of the debate, because it adds fullness to the entire topic - except the other side always lacks the capability to have that debate.

I have tried to lead by example by taking an interest in your thinking and your posts, and critically reading some of the science behind them but you won't return the favour or make any effort to engage in material outside what you post - or have a meaningful debate even on your own material - and not just with me. "Wilful ignorance", as another poster put it. Clearly, you won't make any effort to expand your horizons, so I'm not going to bother engaging your posts any more. Given your preferred comfort zone I'm sure this suits you just fine.

 

Actually, I think I've engaged vigorously with you. You just don't like the outcome. Continue or not, as you wish. I will not be affected.

 

It's a good point. Scientific accumulation of knowledge is, as you probably know, iterative or accumulative. It usually starts with the breakthrough and then it is verified. Given that the publication is in Nature, which is very prestigious, it would have undergone quite rigorous peer review. There will probably be a dozen or so publications that stem from the same data set and team, so it'll be interesting to see as the story unfolds.

I wouldn't dismiss the fact that it is proxy data, though. Basically any inference about an active system prior to modern measuring devices is by proxy! We can describe with some confidence the climate and geology of the world going back many millions of years. How carefully and meticulously it has been categorised and studied. Yet, this is all via proxy data of course.

 

Well again, I see that it was published in nature as being an appeal to authority and I am not sure how much credibility I would give to "peer" reviews of novel research since there really wouldn't be any true peers. One of the proxy measures, for instance is particulate size. That was assumed to follow certain patterns based on research done in the Farallones but we now know that is not the case at all now that we have the technology to reach the deeper depths of the ocean to study the sea floors and recover samples. Particulate size can vary significantly based on location so how you get from there to particulate size showing the speed of the gulf stream seems to me, at least, to possibly be more theoretical assumption along the lines of the Farrallones research than established science.

Anyway, this research may or may not be accurate. My science curriculum heavily emphasized skepticism so I would need a bit more before I take it for gospel the findings are a likely more accurate than not. I personally would have greater confidence in a trend based on a large number of real world measurements taken over 15 years across all 4 seasons over one that is manufactured off novel estimates of a thousand years. I don't have a proof beyond all doubt standard. I just trust direct measurements over estimates.

 

The ocean currents speeding up are wind driven currents.

 

Except, of course, that the acceleration is described as "deep-reaching."
Any excuse in a storm, I guess.
The problem for alarmists is that regardless of what cause is cited, accelerated current is the opposite of what was predicted.

 

A presentation that includes graphics.

A 30-year reconstruction of the Atlantic meridional overturning circulation shows no decline
Charles Rotter
Climate model and paleo-oceanographic research suggests that the AMOC may have been declining for decades or even centuries before this; however direct observations are sparse prior to 2004, giving only…

Emma L. Worthington1, Ben I. Moat2, David A. Smeed2, Jennifer V. Mecking2, Robert Marsh1, and Gerard D. McCarthy3

• 1University of Southampton, European Way, Southampton, SO14 3ZH, UK
• 2National Oceanography Centre, European Way, Southampton, SO14 3ZH, UK
• 3ICARUS, Department of Geography, Maynooth University, Maynooth, Co. Kildare, Ireland

Received: 16 Jul 2020 –

Discussion started: 14 Aug 2020 –

Revised: 09 Dec 2020 –

Accepted: 21 Dec 2020 –

Published: 15 Feb 2021

Abstract
A decline in Atlantic meridional overturning circulation (AMOC) strength has been observed between 2004 and 2012 by the RAPID-MOCHA-WBTS (RAPID – Meridional Overturning Circulation and Heatflux Array – Western Boundary Time Series, hereafter RAPID array) with this weakened state of the AMOC persisting until 2017. Climate model and paleo-oceanographic research suggests that the AMOC may have been declining for decades or even centuries before this; however direct observations are sparse prior to 2004, giving only “snapshots” of the overturning circulation. Previous studies have used linear models based on upper-layer temperature anomalies to extend AMOC estimates back in time; however these ignore changes in the deep circulation that are beginning to emerge in the observations of AMOC decline. Here we develop a higher-fidelity empirical model of AMOC variability based on RAPID data and associated physically with changes in thickness of the persistent upper, intermediate, and deep water masses at 26∘ N and associated transports. We applied historical hydrographic data to the empirical model to create an AMOC time series extending from 1981 to 2016. Increasing the resolution of the observed AMOC to approximately annual shows multi-annual variability in agreement with RAPID observations and shows that the downturn between 2008 and 2012 was the weakest AMOC since the mid-1980s. However, the time series shows no overall AMOC decline as indicated by other proxies and high-resolution climate models. Our results reinforce that adequately capturing changes to the deep circulation is key to detecting any anthropogenic climate-change-related AMOC decline. . . .


Figure 1(a) World Ocean Circulation Experiment (WOCE) North Atlantic A05 section of neutral density γn (kg m−3) at 24∘ N, July or August 1992. From the WOCE Atlantic Ocean Atlas Vol. 3. (Koltermann et al., 2011). (b) Schematic of four dynamic layers to be represented within the regression model by density anomalies at the western and eastern boundaries at a depth within each layer. The density anomalies are represented by the circular markers. (c) Profile of RAPID-estimated mean mid-ocean transport and the resulting northward and southward layer transports. Mean AMOC depth is around 1100 m.

 

https://www.sciencemediacentre.org/...ntic-meridional-overturning-circulation-amoc/

Some of what you say is mirrored by other commentators. But as also pointed out, it's a bit concerning because even though Gulfstream collapse is a long way away, if it does happen it will have major impact. I think it will be interesting if they can find further proxy data to bolster the three modality that they already have. They will also need to explain why there was a change in the early 19th century.

Have you got a link discussing the bit in bold?

 

Opens as a PDF https://pubs.usgs.gov/circ/c1198/chapters/090-100_Sediment.pdf

As for the early 19th century, that period saw low solar activity combined with the Tambora volcanic eruption. That is an era where proxy temperature reconstructions are particularly problematic so researcher rely more on weather observations. There wasn't as much ice in some places like there normally was (like in the waters around greenland) and ships' logs observed a lot of sea ice in places where it was unexpected for the time of year they were in. Weather patterns were off kilter for awhile.

 

Doomsday AMOC “Tipping” Claimed In ‘Nature’ Already Refuted…New Study: AMOC “Shows No Decline”
By P Gosselin on 27. February 2021

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A recent study appearing in Nature, “Current Atlantic Meridional Overturning Circulation weakest in last millennium“, authored by Caesar et al, hints at a global climate system on the verge of tipping out of control.

According to their findings, the weakening of the so-called Atlantic Meridional Overturning Current (AMOC) in the 20th century is “unprecedented”, and likely because of man-made climate change.

The paper claims that there was “a long and relatively stable period” that was then followed by “an initial weakening starting in the nineteenth century, followed by a second, more rapid, decline in the mid-twentieth century.” The AMOC has since reached “the weakest” level in recent decades.

Rahmstorf’s doomsday scenario

Also not surprising: one of the authors of the doomsday-like paper is climate über-alarmist researcher Stefan Rahmstorf of the Potsdam Climate Institute in Germany.

According to Rahmstorf, the Gulf Stream “passing its tipping point” would lead to significant northern Atlantic sea level rise, a regional cooling and “massive effects on the entire ecosystem in the North Atlantic”.

No consensus – contradicted even before release

But the paper’s claims were contradicted already six days before its release. So much for consensus.

A new paper by Worthington et al, “A 30-year reconstruction of the Atlantic meridional overturning circulation shows no decline“, tells us there’s been no decline, let alone a “weakest state”. . . .

 

And when necessary, edited to match the theory that CO2 determines the earth's surface temperature -- e.g., when Michael Mann made the Medieval Warm Period and Little Ice Age not to have happened in his notorious hockey stick graph.