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Topic: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial (Read 436 times) previous topic - next topic

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  • Martin.au
  • Thingyologist
Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Haven't had a good look at this yet. It's an epic project. Following Dave's primitive ramblings on C14 I thought this might be interesting.

https://www.nature.com/articles/s41467-017-00577-6
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • F X
  • The one and only
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #1
pity reply
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #2
Quote
An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.

Here we see a cameo of everything that has gone so horribly wrong with climate science.  Now we codify a model in a deeply non-linear system with ill-understood or unknown feedbacks, don't demonstrate any predictive skill yet claim it has some relevance.  This model is entirely unvalidated and has zero demonstrated predictive skill.  So what we do then is to make more of them and call them an 'ensemble' in an effort to credit them with more skill en masse than any individual model.  The paradigm has become that the average of invented bullshit must be true.

The "ensemble of transient meltwater simulations" shows precisely the square root of fuck all other than the guesses of the people who codified the simulations.

  • MikeS
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #3
Cephus0 becomes a climatologist modeling genius ITT.

  • F X
  • The one and only
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #4
Here we see a cameo of everything that has gone so horribly wrong with climate science.
I disagree.  They are trying to figure out why things happened as they did, in the past.   The deep ocean conveyor is a very important thing to understand.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

  • F X
  • The one and only
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #5
While the amount of heat transported by the oceans is estimated to equal the atmosphere, the mechanism is driven by salinity and the sinking of cold water.  Fresh water from melting ice (on land) can change the amount of deep water transport, seriously changing the global climate.

https://oceanservice.noaa.gov/facts/conveyor.html

Changes in the arctic actually can change the climate in Antarctica, and possibly the other way around.  It's complicated, but fascinating.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

  • F X
  • The one and only
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #6
For example.

If a warming period happens that causes a large release of fresh water into the arctic, it reduces the amount of cold salty water sinking there.  First, fresh water floats on top of salt water, allowing much faster freezing in the winter, reducing the cooling of the surface waters.  This actually keeps the ocean warmer, meaning less salt water sinks, meaning the deep ocean conveyor current is reduced.  This will show up later, exactly how much later is actually unknown.

Second, cold fresh water will not sink, so it actually changes the general circulation of the oceans.

The amount of time for the Thermohaline Circulation to complete a cycle (meaning the water makes a full loop) ranges from 100 years, to 4000 years.  (this is something we really need to actually know)

The estimate for the oldest cold water from Antarctica to upwell in the north Pacific is 1000 years.  But that isn't actually known.

It is hypothesized that this fresh water influx can alter the global climate, and it is possible it is one driver of global climate change.  Certainly something causes small changes in the amount of summer sunshine the NH receives to change the global climate.

It's all quite interesting.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #7
Here we see a cameo of everything that has gone so horribly wrong with climate science.
I disagree.  They are trying to figure out why things happened as they did, in the past.  The deep ocean conveyor is a very important thing to understand.

I've no problem whatsoever with people trying to get a handle on things using numerical simulations.  The problem is that modern climate science goes on from there to treat the output of what are at best sketchy speculation as some sort of actual result.  None of it is any kind of a result until it progresses to the level of highly significant predictive skill.

Additionally whenever you see the word 'ensemble' with respect to climate modelling you know that you are dealing with zero predictive skill and this is the fudge to cover for that dismal fact.  Either you have a model which makes accurate predictions or you don't.  Having ensembles covering all conceivable system behaviours and using post hoc weightings which track the actual as-measured climate is becoming the new norm and obviously enough will never be wrong in the present but will likely never predict a thing correctly - but that doesn't matter because you simply adjust accordingly using your real world data-modified ensemble weightings in the future.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #8
Here we see a cameo of everything that has gone so horribly wrong with climate science.
I disagree.  They are trying to figure out why things happened as they did, in the past.  The deep ocean conveyor is a very important thing to understand.

I've no problem whatsoever with people trying to get a handle on things using numerical simulations.  The problem is that modern climate science goes on from there to treat the output of what are at best sketchy speculation as some sort of actual result.  None of it is any kind of a result until it progresses to the level of highly significant predictive skill.

Additionally whenever you see the word 'ensemble' with respect to climate modelling you know that you are dealing with zero predictive skill and this is the fudge to cover for that dismal fact.  Either you have a model which makes accurate predictions or you don't.  Having ensembles covering all conceivable system behaviours and using post hoc weightings which track the actual as-measured climate is becoming the new norm and obviously enough will never be wrong in the present but will likely never predict a thing correctly - but that doesn't matter because you simply adjust accordingly using your real world data-modified ensemble weightings in the future.
you have a very backwards understanding of models involving nonlinear behavior. I'm not saying anything about whether or not your global climate model is better or worse than the one that the planet's climate scientists are working on, just that your request here is assuming a cybernetic reality with no butterflies. You can only tune a dynamic systems model using historical data and they aren't predictive in the same way a linearized model is predictive. Also, when your timescales are decades and centuries... well...
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #9
Yes indeed.  We humanzee throwbacks have that wild primitive hypothesis testing notion even now in the brave new modelworld.  We subscribe to the embarrassingly archaic view that hypotheses should reliably predict things.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #10
you can't predict a nonlinear system.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #11
Also, when your timescales are decades and centuries... well...
This is where Hari Seldon's model broke down!

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #12
had to google that one.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #13
It's all quite interesting.
Interesting? That's a bit of an understatement. The Gulf Stream has an important effect on climate in Northern Europe. The possibility that this could be disrupted is worrying. More discussion here.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #14
you can't predict a nonlinear system.

Yes you can.  If you understand the nonlinearities.  The acid test of course is can you make reliable predictions over more than a few timesteps.  It's a testing thing you know.  If people think they can for a coupled nonlinear system like the climate then they should make the predictions and let's see.  I know it's a bit backwards to express scepticism when people say they can predict the future but just indulge me anyway.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #15
Also, when your timescales are decades and centuries... well...
This is where Hari Seldon's model broke down!


And that is really about where we are with climate modelling.  It's pure science fiction yet is for some bizarre reason completely isolated from the normal strictures of science.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #16
you can't predict a nonlinear system.

Yes you can.  If you understand the nonlinearities.  The acid test of course is can you make reliable predictions over more than a few timesteps.  It's a testing thing you know.  If people think they can for a coupled nonlinear system like the climate then they should make the predictions and let's see.  I know it's a bit backwards to express scepticism when people say they can predict the future but just indulge me anyway.
Irt's a nomenclature issue but any nonlinear system you can predict has massive externalized aka linearized, functions. So no. It is actually an important deal that you cannot predict a nonlinear system. People often try to qualify that with "you need to know the initial conditions" but that's just engineering for "you've got to pick where you linearize" because there are no closed systems.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #17
had to google that one.
Sorry, forgetting my age!

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #18
you can't predict a nonlinear system.

Yes you can.  If you understand the nonlinearities.  The acid test of course is can you make reliable predictions over more than a few timesteps.  It's a testing thing you know.  If people think they can for a coupled nonlinear system like the climate then they should make the predictions and let's see.  I know it's a bit backwards to express scepticism when people say they can predict the future but just indulge me anyway.
what we can do, and I need to preface this by saying I don't pay any attention to this debate at all so this may be what climate scientists actually do, is model the attraction basins to understand what constitutes state flips and where state collapse is likely irreversible.

You must be an engineer.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #19
had to google that one.
Sorry, forgetting my age!

Nah, I'm the right age, just never got into scifi.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

  • Fenrir
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #20
<snip>... I know it's a bit backwards to express scepticism when people say they can predict the future but just indulge me anyway.

I'm predicting the future right now and I think my chances of being correct are excellent.

It's what plants crave.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #21
If a warming period happens that causes a large release of fresh water into the arctic, it reduces the amount of cold salty water sinking there.  First, fresh water floats on top of salt water, allowing much faster freezing in the winter, reducing the cooling of the surface waters.  This actually keeps the ocean warmer, meaning less salt water sinks, meaning the deep ocean conveyor current is reduced.  This will show up later, exactly how much later is actually unknown.

Second, cold fresh water will not sink, so it actually changes the general circulation of the oceans.

The amount of time for the Thermohaline Circulation to complete a cycle (meaning the water makes a full loop) ranges from 100 years, to 4000 years.  (this is something we really need to actually know)

The estimate for the oldest cold water from Antarctica to upwell in the north Pacific is 1000 years.  But that isn't actually known.

It is hypothesized that this fresh water influx can alter the global climate, and it is possible it is one driver of global climate change.  Certainly something causes small changes in the amount of summer sunshine the NH receives to change the global climate.

From the Realclimate article I linked:

Quote
]There are, therefore, two reasons why thus far we could have underestimated the risk of a breakdown of the Gulf Stream System. First, climate models probably have a systematic bias towards stable flow. Secondly, most of them do not take into account the melting ice of Greenland.

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #22
It's all quite interesting.
Interesting? That's a bit of an understatement. The Gulf Stream has an important effect on climate in Northern Europe. The possibility that this could be disrupted is worrying. More discussion here.

those links are examples of modeled attractor basins and state flips. That, in fact, is what models of dynamic nonlinear systems are good at. They can alert us to the dynamics of persistence and let us understand the boundaries of the tolerances in variability.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #23
Here we see a cameo of everything that has gone so horribly wrong with climate science.  Now we codify a model in a deeply non-linear system with ill-understood or unknown feedbacks, don't demonstrate any predictive skill yet claim it has some relevance. 

The model used in this paper was not created to make predictions or forecasts, and the paper does not offer any predictions or forecasts.
  • Last Edit: March 14, 2018, 06:39:39 AM by Autonemesis

  • F X
  • The one and only
Re: Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Reply #24
It's all quite interesting.
Interesting? That's a bit of an understatement.
Yes, I tend to use "interesting" for things like three reactors melting down and threatening the entire world.  Most people just don't actually care that much, but I find it interesting.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭