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A forthcoming collapse of the Atlantic meridional overturning circulation

nature.com

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Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#61

Post by sieste »

braaannigan wrote: post #50

I've got a background in this field and I am very surprised to see this published in Nature. The model presented is purely statistical with no representation of the underlying physics. When we are dealing with a phenomenon that is driven by well-understood physical laws (e.g. geophysical fluid dynamics, radiation physics etc) then these physical models are the most reliable basis for prediction. When I say physical m…

> physical models are the most reliable basis for prediction

Simpler models can yield better predictions than complex ones, even when the complex model is more "realistic". The many tunable parameters and complex feedback loops can increase uncertainty compared to a simple model.

See for example "To explain or to predict?" by Shmueli (2010, https://doi.org/10.1214/10-STS330)

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#63

Post by retrocryptid »

oceanthrowaway wrote: post #32

I’m a physical oceanographer. While I have only skimmed this article I would like to make two quick comments. 1) The AMOC is one of the most studied parts of the world ocean and predictions about its collapse have been made since Stommel in 1961. I think in general any study on its imminent collapse should be taken with a grain of salt and it would be wise to wait for further replication and the consensus of the comm…

Are you comparing Stommel's Box model to Bower's recent work? I would argue the latter is more "expressive" though yes, it depends on measurements we weren't collecting in the 60s.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#64

Post by [deleted] »

pvaldes wrote: post #52
richardwhiuk wrote: post #22

Earlier quoted context omitted.

Given a full collapse, wouldn't the UK resemble northern Canada?

There is a good way to see the problem in a second Think about New York, is at 40 degrees N latitude. This means that if NY would be in the Atlantic coast of Europe would fall in Portugal! a little North to Lisbon! (38ºN). Sometimes Is easy to forget that NY is "Southern Europe" league. Southern than the North Coast of Spain. Now lets see Quebec (53ºN). Well, London is 51ºN. Without the sea current bringing hot tropi…

[deleted]

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#65

Post by bamfly »

Projectiboga wrote: post #44
rcarr wrote: post #11

Anyone else think that all these predictions are going to happen sooner rather than later in terms of the given prediction range? I can't help but think that a study focussing on a specific area like this one, antarctic sea ice, wildfire predictions etc must only be able to take so many variables into account and that second order effects, third order, fourth order and beyond from other climate subsystems are going t…

Yes the timeline for complete shift is before 2030. NYC weather is already temporarily altered each spring snd early summer with all the cold water from the Greenland melt, and that is just a slight shift away from there in the Gulf stream. When these shifts happen it's in about a dozen years. The last 8 years are the hottest in at least 150 years.

Are we expecting colder, or warmer weather in NY and New England from this? It's not clear to me from reading some of these articles. The expected effect for Northern Europe—that I understand.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#66

Post by oceanthrowaway »

retrocryptid wrote: post #63
oceanthrowaway wrote: post #32

I’m a physical oceanographer. While I have only skimmed this article I would like to make two quick comments. 1) The AMOC is one of the most studied parts of the world ocean and predictions about its collapse have been made since Stommel in 1961. I think in general any study on its imminent collapse should be taken with a grain of salt and it would be wise to wait for further replication and the consensus of the comm…

Are you comparing Stommel's Box model to Bower's recent work? I would argue the latter is more "expressive" though yes, it depends on measurements we weren't collecting in the 60s.

No I am just noting that the AMOC bistability literature is decades long.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#67

Post by AndrewKemendo »

braaannigan wrote: post #50

I've got a background in this field and I am very surprised to see this published in Nature. The model presented is purely statistical with no representation of the underlying physics. When we are dealing with a phenomenon that is driven by well-understood physical laws (e.g. geophysical fluid dynamics, radiation physics etc) then these physical models are the most reliable basis for prediction. When I say physical m…

Based on my initial reading so far this seems like the best take.

However, I’ll offer an alternative perspective.

This paper identifies that IPCC does not expect a collapse in the 21st-century. That alone should be our largest biasing factor when we’re asking - from a time horizon perspective - what should we be doing?

So then, why now? I think it’s compelling that they identified two preconditions for a collapse they have been monitoring, and now are indicating that we are on the trajectory towards collapse, given what we were looking for for indications and warning.

As a former military officer, the key thing that you get from intelligence is long-term forecasting and indications and warnings for negative or dangerous actions by your adversaries and risk-taking by your allies.

So following that same logic, then if two of the largest indications and warnings for a future energy transfer collapse/flip scenario, based on the best modeling we have today, are indicating that we are on that trajectory, then it seems appropriate for the most well respected journal to relay that fact.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#68

Post by whalesalad »

braaannigan wrote: post #50

I've got a background in this field and I am very surprised to see this published in Nature. The model presented is purely statistical with no representation of the underlying physics. When we are dealing with a phenomenon that is driven by well-understood physical laws (e.g. geophysical fluid dynamics, radiation physics etc) then these physical models are the most reliable basis for prediction. When I say physical m…

The collapse needs to be discussed more. The only way for that discussion to occur is if research is published.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#69

Post by jmclnx »

kneebonian wrote: post #9
mschild wrote: post #7

An article from livescience.com that may be worth a read. TLDR: if slowdown occurs, temperatures could drop by 5C in Europe and North America. What a 5C drop actually looks like they don't say. https://www.livescience.com/planet-earth/climate-change/gulf...

So if this continues it will result in a 5C drop in temprature across North America and Europe? Am I understanding this correctly. Which for reference a 5C drop should mean that New York is covered in glacier according to this source https://xkcd.com/1732/

The Ave Temp of the world is rising and from what I read and hope I understood, nothing will really stop that, all we can do is hope to lessen the temp rise.

So, I think this "5C" drop in East NA and West Europe will be absorbed throughout the world. So those regions will still have higher ave temp then say 1950, just a bit less than the rest of the world.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#70

Post by sieste »

bullen wrote: post #62

So what would the consequences be? ~3-5 degree drop in temperature at the coasts?

Something on the same order of magnitude as projected global temperature increase. That's why you see a white/blue blob in the North Atlantic on maps of temperature trends.

https://commons.wikimedia.org/wiki/File:NCDC_temperature_tre...

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