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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

#81

Post by SirMaster »

post-it wrote: post #17
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…

Oh absolutely. Environmental scientists are very conservative and anti-alarmist with their predictions, and every successive generation of derived data skews towards the more conservative end.

You are saying there are no scientists that predicted we would have more sea level rise than we actually do by now?

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#82

Post by braaannigan »

sieste wrote: post #61
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 )

Many of the physical models are of similar complexity to the model in this paper - the sort of analytical model that you run in a few minutes on your laptop, not on a super-computer. It's not a question of complexity it's about whether a statistical model that is not constrained by well-understood constraints is a high-value model

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#83

Post by Terretta »

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…

The terms "imminent" and "predict the time" seem like missing the point of the article you acknowledged you have only skimmed.

I felt the article was clear collapse is not imminent, not even in this century.

I felt it noted focus was not on imminence, but on changes worth mentioning in aspects of interest.

Perhaps the difference is this article is talking of timing for transitions of significance, rather than the forthcoming collapse more likely to arrive sooner after such transitions?

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#84

Post by CamperBob2 »

braaannigan wrote: post #74
gwerbret wrote: post #58

Earlier quoted context omitted.

The publication is in Nature Communications , which is a bit of a different (lesser) beast than Nature .

Thanks for pointing this out, I missed that

This is becoming a perennial refrain in HN stories based on scientific papers. ("Oh, wait, this dubious study or lazy meta-analysis isn't really appearing in Nature, it's some other publication to which Nature has whored out their name and credibility.")

It sounds like the 150-year-old scientific journal of record has been taken over by private equity, or by MBAs with KPIs to optimize.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#85

Post by IKantRead »

fmstack wrote: post #46
snowwrestler wrote: post #29

Earlier quoted context omitted.

Ireland and Great Britain are at about the same latitude as Labrador in Canada, but benefit from heat transported across the North Atlantic from the Caribbean by warm water. Absent the current that is transporting that warm water, one would expect the GB climate to more closely resemble Labrador’s. In other words, much colder.

not gonna lie, a scenario where a big nasty effect of climate change pastes Europe first might make the powers that be wake up to the impending disaster faster. For the folks with the big money one death in Europe might be more shocking than 100 deaths in India.

The trouble with climate change has always been that by the time you notice the "big nasty effect" it's already too late to prevent catastrophe.

To be clear, it's never too late to improve our fate, but by the time something like the AMOC shutting down destroys Europes climate, you've already signed up for an incredible amount of climate pain. Maybe such an event will wake us up enough to prevent out right extinction, but if this happened the collapse of industrial civilization would be virtually guaranteed.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#86

Post by stoneman24 »

mschild wrote: post #51
SkyMarshal wrote: post #33

Earlier quoted context omitted.

Pretty sure Europe will heat up, NA will cool down. Currently the Atlantic current brings hot water from the equatorial zones up the US east coast, hence the humidity there. And it brings cool water down from the Arctic to Europe’s west coast, hence the mild non-humid climate there. Reversing the current would reverse that dynamic. It might make Europe less suitable to wine growing, for one, which requires mild cool…

The current wouldn't reverse, it would stop or become a lot slower. So cold water would stay in the artic regions and warm water closer to the equator. I suppose you could compare this to one giant heat pump, circulating a heat source to Europe and North America that makes life livable.

As I understand it, the warmer the water, the stronger and more powerful the hurricane. So bigger and more hurricane in the mid-latitudes (Caribbean, southern US). Not a good prospect, at all.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#87

Post by malloci »

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…

Skepticism on this was called out in WaPo's article on the same subject:

Other experts on the AMOC also cautioned that because the new study doesn’t present new observations of the entire ocean system — instead, it is extrapolating about the future based on past data from a limited region of the Atlantic — its conclusions should be taken with a grain of salt.

Source: https://www.washingtonpost.com/climate-environment/2023/07/2...

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#88

Post by fwungy »

In the big picture of the geologic time scale we are at risk for an ice age soon enough. The normal state of the Earth is cold and icy, but still habitable, perhaps barely. No one is sure why the ice ages happen, the most popular theory is that it's caused by perturbations in Earth's orbit.

Re: A forthcoming collapse of the Atlantic meridional overturning circulation

#90

Post by Biologist123 »

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…

As a lay-bystander to the climate debate, I get a little spooked when I see comments like this. Like 99.9% of people, the science of complex climate systems is beyond me as are the de facto black box models that project climate change. Instead I use “appears in a credible journal” as a basis for trusting the apparent direction of travel and I’m disconcerted when I see that proxy challenged. I also, I am somewhat sorry to say, likely to discount anonymous comments as credible as there is so much propaganda in this space. That’s not to say I don’t understand the challenge of modeling complex systems, but want to point out that one of the most frustrating things about the climate debate is that the battling sides require us to take on trust what they tell us for some very big changes. It’s difficult.

Question for the community: how does one navigate such uncertainty?

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