Winter 2023/24 Chat and Discussion

[raz.org.rain]

1 hour ago, CryoraptorA303 said:

Fair enough, these battleground fronts will also happen more often due to climate change via more intense weather patterns.

I do apologise, I can't put this any more politely, but this is a diabolical understanding of the topic.

The Gulf Stream and AMOC are two completely different things. The Gulf Stream is a permanent northwesterly current caused by the rotation of the Earth and will not collapse. AMOC is the thermohaline component that may collapse due to climate change.

The effects of an AMOC shutdown are completely misreported in common media. The actual cooling would be limited to high latitude and England would, after some decades, see a cooling of less than a degree. The much more significant impact is the aridifying of the European climate due to the loss of a warm Atlantic to deliver frequent cyclones to Europe's shores. The aridification that the UK's climate would experience would seriously threaten agriculture in this country. It may not seem like it but our agriculture relies on the frequent rainfall we receive and a significant reduction in precipitation (>20%) would be a disaster.

Moreover, as with Subpolar Gyre slowdown or collapse, which may actually be happening, a collapse of AMOC would likely cause an expansion of the Hadley cell, which would lead to a drier, hotter summer. See how many dry, hot summers in this country occured with a cool Atlantic. The Jet Stream would also be weakened and move northward, as may be occuring with the Subpolar Gyre slowdown, contributing to the omega blocking.

Lastly, the original research into this topic was done with palaeoclimate proxies from Younger Dryas, a time with a cooler climate than today and when significant ice sheets still existed over Europe. Considering the likely warming that will have occurred by the time AMOC is likely to collapse (if it does, more on that later), on top of how much warmer the climate already is vs that period, the effects of an AMOC interruption or shutdown in Younger Dryas are really not comparable to today.

As for the Danish "believing in" an AMOC collapse, this is a really bad understanding of the scientific method, but I won't go into a self-indulgent exploration of that as this post is already long and pretentious enough. That research team's model is just one model, and the general consensus is that an AMOC collapse is very unlikely in this century. The actual risk of an AMOC collapse is based upon older research that suggested it was weakening, but later research has been... less optimistic in how much its actually weakening by. Some has even suggested its not appreciably weakening at all, which would in turn suggest an AMOC collapse may not happen at all.

In summation, an AMOC collapse is most likely an overstated fear, and is far from settled science. Most importantly, it's currently very unlikely that any of us here will see a significant slowdown or collapse in our lifetimes. The much more pertinent teleconnective disruption at the moment is the Subpolar Gyre, one component of AMOC, and the slowdown or shutdown of that will likely do nothing but milden our winters and heat and dry our summers.

However, science is constantly evolving, and of course climate change is now happening very fast and the situation is changing almost day by day, so in 10 years the situation with AMOC may be significantly different, however we can't know either way. As touched upon, by the time an AMOC collapse would actually be likely to happen, probably after this century, with the trajectory we're on, the globe will have warmed by so much that any potential cooling that an AMOC collapse would provide will have been cancelled out a long, long time ago and instead it will just contribute to heating our already very hot compared to now summers even further.

AMOC theory is a constant source of annoyance when discussing climate change for me, it's a prime example of everything that's wrong with climate change discourse. It's incredibly frustrating how widely misrepresented it has been over the past few decades. 

[raz.org.rain]

13 minutes ago, Don said:

I would take that, especially if the rest of winter isn't up to much and although there is still two months to go, the current signs are not great!  Any SSW now likely to be mid February, similar to last year?

I don't mind an SSW in February as long as it stays in February and doesn't have cascading cold effects all the way into May.

 

Edit: also I'm not sure how some can be so convinced that a large cold reserve in Scandinavia can increase the potential for extreme cold here. The geography of Northern Europe is more likely to lock pressure systems over Scandinavia and cause it to pool and disperse there surely? The British Isles have always had a western (Atlantic) and southern (continental) bias when it comes to falling under the influence of neighbouring weather systems.

Edited December 31, 2023 by raz.org.rain

[CryoraptorA303]

3 minutes ago, raz.org.rain said:

AMOC theory is a constant source of annoyance when discussing climate change for me, it's a prime example of everything that's wrong with climate change discourse. It's incredibly frustrating how widely misrepresented it has been over the past few decades. 

Agreed. I see it as a kind of equivalent to the effect of persistent depictions of incorrectly-oriented wrists and scaly Velociraptors on discourse of dinosaurs; it's immensely damaging to the public's knowledge of the topic.

12 minutes ago, raz.org.rain said:

I think it depends on which parts of the north too. For example around the Cheshire plains area, we seem to get at least 30 every summer from what I can tell. Lowlands England is often better placed for hotter weather.

I neglected to mention that; elevation is an extremely important factor in the British climate.

[CryoraptorA303]

43 minutes ago, DCee said:

The dafs will be out even earlier this year! Forget the talk of a colder second half of January, more like early Spring. Greater chance of verifying considering where we are.

16C in the Jan sunshine anyone?

Forgetting the blocking due mid March of course....

It wouldn't even surprise me at this point. Hell, we might as well go for a record break at this point - 18.5-19.4C at Kew Gardens or St James's Park. Or perhaps East Malling again. If we're going to have extremely mild conditions for the time of year, we might as well set a new record.

On the topic of daffodils, we have shoots in the garden now On December 31st no less. I believe this is a new record for our garden. Not even December 2015 got this far if I recall.

Edited December 31, 2023 by CryoraptorA303

[*Stormforce~beka*]

6 hours ago, stewfox said:

Just read through 7 pages on the Model Output thread covering the last 6hrs !

The charts are good,bad  indifferent . Winters over ,cold delayed 

So much conflicting drama, one liners and and different takes on the same model. Enough to give you a headache. 

I love it

 

I've not been in there yet ...

[*Stormforce~beka*]

30 minutes ago, Don said:

I would take that, especially if the rest of winter isn't up to much and although there is still two months to go, the current signs are not great!  Any SSW now likely to be mid February, similar to last year?

Peee off!!!

[Don]

Just now, *Stormforce~beka* said:

Peee off!!!

Well, you'd better hope that January and (or) February delivers something decent then!! 

[*Stormforce~beka*]

Just now, Don said:

Well, you'd better hope that January and (or) February delivers something decent then!! 

It won't ... 

[Harsh Climate]

19 minutes ago, CryoraptorA303 said:

I'm happy that you liked where you grew up, can't say the same for round here. Always been a horrible place in many ways and I can't wait to escape I should probably add I'm not strictly originally from Kent, I'm originally from Ilford in East London and moved here when I was 8.

I suspect I'm a bit further south than you were as I'm in the Medway valley and we often get shafted. We got nothing apart from a very light dusting in around January 2015 I want to say, from March 2013 to BFTE. After BFTE it took until February 2021, and then of course last December. Assuming no other cold spell comes up this year, I suspect it'll be some time until we have significant snow again here. I would say "if ever", but of course the chances are we will have it again at some point.

December 2009, January 2010 and December 2010 are some of my best memories. February 2012 and the various shenanigans of 2012/13 as well. I wish we could have winters like that as a default. Oh well

I'm glad my preachy pretentiousness wasn't offensive. I know I can come across as very rigid, condescending and extraordinarily preachy sometimes, that's not my intention and I'm just a very scientifically-oriented person who gets frustrated easily.

As I said, the Gulf Stream isn't the same thing as AMOC. The Gulf Stream is a separate current that won't collapse as it is caused by the rotation of the Earth and so it's a physical phenomenon. Popular media often treats them as the same thing, leading to a lot of confusion with the public.

AMOC can certainly be weakened or collapse, and we know out of it's roughly 2.5 million year history it has strenghened, weakened and collapsed many times. The difference is, this is something that happens on the scale of thousands of years and we still don't know all that much about it and exactly what causes it to weaken or collapse, or when it might happen. Many, many people have researched this and overall, it would appear that such a collapse is unlikely to happen in this century.

My solution to the AMOC problem is that until the science on it is more settled, we shoudn't really bother to talk about it in regards to the shorter term, as in all likelihood is it not a looming threat and there are several other teleconnections and phenomena that will be disturbed long before AMOC is likely to be.

Note that I use the word "likely" a lot here as there are very few, if any certainties in changing fields of science.

Yes, they undoubtedly will and we will continue to have more and more December 2023s, February 2019s, January 2014s and December 2015s as time goes on, and less and less December 2010s. In 50 years time (2073), a December 2015-like winter month is highly likely to be the norm, if not outright cooler than average. February 2019 would also be relatively normal and many winters will see temperatures in excess of 20C at least once, although probably not quite all. December 2073 will likely have an average daily maximum somewhere in the range of 11-13C and daily minimum 7-8C, with a maximum of perhaps 16-18C. January and February will be very similar, with January 2074 having slightly lower on all stats and February 2074 having a slightly higher average daily maximum, slightly lower daily minimum and a somewhat higher maximum, probably 18-20C.

What should be kept in mind is we will always have cooler than average months, and we will always have cold winter months. Even as far south as Morocco and Algeria can occasionally have overnight snow. Parts of the Levant have had outright snowstorms even at lower altitude on occasion. One cold winter month or significant cold snap like December 2010 does not mean the climate isn't warming. The important part is the trend in the long-term data, and average temperatures have increased by over one degree C since 1961-1990, in some locations close to 2C in certain months. The increasing wetness in high autumn, and the drying of September, is also a big indicator of a warming climate.

Those arguments are wrong, as you already seem to suspect I won't go into the full dossier here as it's frankly far too much info to put in a single post, but both mid- and long-term climate data, atmospheric proxies and palaeological proxies all support climate change. The increase in atmospheric carbon dioxide since 1800 is also a very near 1:1 match with rising temperatures. The most damning thing is probably stratospheric temperatures. In the same timeframe, the stratosphere has cooled at the same rate as the troposphere and the surface has warmed. Were the warming caused by an outside factor like the Sun, the stratosphere would warm, not cool. The cooling of the stratosphere means heat is being reflected away from it, suggesting something in the lower atmosphere is trapping more heat from the Sun. You cannot have a cooling stratosphere with anything other than greenhouse gas-caused warming, and humans are the only source of rising carbon dioxide and methane levels in recent history

Hopefully this second pretentious, self-indulgent post clears those things up

I think I could learn a lot from you   Where you been hiding lol.

''Yes, they undoubtedly will and we will continue to have more and more December 2023s, February 2019s, January 2014s and December 2015s as time goes on, and less and less December 2010s. In 50 years time (2073), a December 2015-like winter month is highly likely to be the norm, if not outright cooler than average. February 2019 would also be relatively normal and many winters will see temperatures in excess of 20C at least once, although probably not quite all. December 2073 will likely have an average daily maximum somewhere in the range of 11-13C and daily minimum 7-8C, with a maximum of perhaps 16-18C. January and February will be very similar, with January 2074 having slightly lower on all stats and February 2074 having a slightly higher average daily maximum, slightly lower daily minimum and a somewhat higher maximum, probably 18-20C.''

I'm going to save these dates and temperature predictions you make, be interesting to see if you are correct, provided I'm still alive! 

 ''My solution to the AMOC problem is that until the science on it is more settled, we shoudn't really bother to talk about it in regards to the shorter term, as in all likelihood is it not a looming threat and there are several other teleconnections and phenomena that will be disturbed long before AMOC is likely to be.''

I will take your word on it then, just that I watched a Discovery Channel program on this subject a few years ago that got me a little excited, like you say many other teleconnections/ phenomena with much more credence than something we know very little about.

 

 

 

[Don]

Just now, *Stormforce~beka* said:

It won't ... 

Well, cold/snowy March it is then! 

[CryoraptorA303]

9 minutes ago, Don said:

Well, cold/snowy March it is then! 

I wouldn't even mind this, to be honest. March 2013 is one of my best memories. As long as it is truly snowy and cold and not just annoyingly cold rain, of course.

Edited December 31, 2023 by CryoraptorA303

[January Snowstorm]

You would wonder if we just stuck with the Met Office long range and forgot looking at the models would we all be much happier. The reality is the models are cropping changing every day beyond 6 or 7 days. Years ago I used to think we had the heads up on the general population with regard to incoming cold. I don't think that anymore because 9 times out of 10 the models get it wrong. Extraordinary in the eve of 2024 that computers still can't forecast the weather beyond a week!!!!! (Something they could do 30 years ago)

[Derecho]

1 hour ago, CryoraptorA303 said:

Fair enough, these battleground fronts will also happen more often due to climate change via more intense weather patterns.

The effects of an AMOC shutdown are completely misreported in common media. The actual cooling would be limited to high latitude and England would, after some decades, see a cooling of less than a degree.

Moreover, as with Subpolar Gyre slowdown or collapse, which may actually be happening, a collapse of AMOC would likely cause an expansion of the Hadley cell, which would lead to a drier, hotter summer. See how many dry, hot summers in this country occured with a cool Atlantic. The Jet Stream would also be weakened and move northward, as may be occuring with the Subpolar Gyre slowdown, contributing to the omega blocking.

I agree with large parts of your post (I also don't think the AMOC will collapse) but it is slowing down.

Warning of a forthcoming collapse of the Atlantic meridional overturning circulation

WWW.NATURE.COM

---

The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system. Here, data-driven estimators for the time of tipping predict a potential AMOC collapse mid-century...

However the impacts of a notable slowdown could be quite dramatic. I did my postgrad at the Oceanography Centre and it was the big research topic given what happened in 2010. I didn't look at that particular topic (I was looking at how atmospheric circulation had an impact on marine temperatures) but I know people who did.

Given atmospheric circulation has a big impact on local temperatures, a slowdown of the AMOC would have big impacts. 2010 was potentially an interesting instance. There is a lot of unknowns about earlier decades, the RAPID array which monitors the AMOC at 26N was only set up in 2004.

Of course climate change will add more heat into the atmosphere but how that additional heat is distributed depends on what atmospheric circulation does. The below figure is interesting but it's run in a scenario where:

- There is a full collapse
- The model is run without consideration of GhG impacts from the point of initiation

Global and European climate impacts of a slowdown of the AMOC in a high resolution GCM

LINK.SPRINGER.COM

---

The impacts of a hypothetical slowdown in the Atlantic Meridional Overturning Circulation (AMOC) are assessed in a state-of-the-art global climate model (HadGEM3), with particular emphasis on Europe. This is...

The UK climate would cool substantially but much of this would be caused by colder winters with summers as you say becoming hotter. Overall there'd be a slight negative feedback on global temperatures with substantial cooling in the northern hemisphere but accelerated warming in the southern hemisphere.

Of course the big unknown would be the impacts of climate change on top of the above simulation. There is also a big difference between a slowdown and collapse.

A lot of unknowns but a very interesting topic that I'd throw my thoughts in.

[MP-R]

41 minutes ago, Don said:

Well, you'd better hope that January and (or) February delivers something decent then!! 

Doesn’t matter. March onwards is spring. No need to ruin that season too just because the previous one couldn’t get its act on!

[CryoraptorA303]

25 minutes ago, Harsh Climate said:

I think I could learn a lot from you   Where you been hiding lol.

Glad to hear it. I've always fancied myself as somewhat of a teacher

26 minutes ago, Harsh Climate said:

''Yes, they undoubtedly will and we will continue to have more and more December 2023s, February 2019s, January 2014s and December 2015s as time goes on, and less and less December 2010s. In 50 years time (2073), a December 2015-like winter month is highly likely to be the norm, if not outright cooler than average. February 2019 would also be relatively normal and many winters will see temperatures in excess of 20C at least once, although probably not quite all. December 2073 will likely have an average daily maximum somewhere in the range of 11-13C and daily minimum 7-8C, with a maximum of perhaps 16-18C. January and February will be very similar, with January 2074 having slightly lower on all stats and February 2074 having a slightly higher average daily maximum, slightly lower daily minimum and a somewhat higher maximum, probably 18-20C.''

I'm going to save these dates and temperature predictions you make, be interesting to see if you are correct, provided I'm still alive! 

Feel free to hold me to it! Assuming no untimely death then chances are I will be alive to see winter 2073/74, in fact I will just be turning 71 in Feb 74, so we'll see how accurate my assessment was. I fear if anything it will have been on the cooler side, but I hope in that time we make some incredible advances and we find a way to seriously curb the warming. I don't think this is very likely though and we are probably headed for a bad-case scenario.

29 minutes ago, Harsh Climate said:

I will take your word on it then, just that I watched a Discovery Channel program on this subject a few years ago that got me a little excited, like you say many other teleconnections/ phenomena with much more credence than something we know very little about.

Indeed, as I mentioned the Subpolar Gyre is changing at a much faster rate and assuming the research produced at COP28 is indeed correct in its analysis, is causing serious changes to Hadley cells and the Jet Stream on a much shorter timescale than AMOC itself can ever hope to achieve.

Don't just take my word for it though! I encourage everyone to do their own research, with reliable and trusted sources, and come to their own conclusion. In my opinion, in this country our mindset far too often to follow what someone we think is trustworthy says without questioning them. No one is beyond criticism, including me, and we need to question our chosen overlords more often than we do. We have a serious media problem in this country where misinformation and lies are rife and I believe the mindset we as a people have do no favours for this. Not to sound like I'm leading any credence to conspiracy theories and the like, I'm not and most conspiracy theories are if anything born from this problem, and climate science is very much settled in that human activity is causing rapid warming, but misinformation is absolutely rife about this and many other science-related concepts. I find that we as a population has an extremely poor grasp of science and have low ability to think critically. The state of our media is a reflection of who we are as a population.

Anyway, this has become extremely preachy, so I'll end it there, but the message is the same. If you become well-versed in the science, you will come to the undoubtable conclusion that our climate is warming, but I don't want anyone to just take my word for it. I would rather people come to the conclusion on their own. I am by no means an expert and I can only point anyone in the right direction if they want to learn more.

Not to confuse the point too much, let me make these things clear: Our climate is warming at an aggressive pace, and it's caused by human activity. My point is that I don't want anyone to just take my word, I would like people to do their own research and come to that conclusion by themselves.

Apologies if this has become a bit wishy-washy, it's New Year's Eve, I've had a few beers and I'm just trying to communicate my inner thoughts

[raz.org.rain]

6 minutes ago, CryoraptorA303 said:

Glad to hear it. I've always fancied myself as somewhat of a teacher

Feel free to hold me to it! Assuming no untimely death then chances are I will be alive to see winter 2073/74, in fact I will just be turning 71 in Feb 74, so we'll see how accurate my assessment was. I fear if anything it will have been on the cooler side, but I hope in that time we make some incredible advances and we find a way to seriously curb the warming. I don't think this is very likely though and we are probably headed for a bad-case scenario.

Indeed, as I mentioned the Subpolar Gyre is changing at a much faster rate and assuming the research produced at COP28 is indeed correct in its analysis, is causing serious changes to Hadley cells and the Jet Stream on a much shorter timescale than AMOC itself can ever hope to achieve.

Don't just take my word for it though! I encourage everyone to do their own research, with reliable and trusted sources, and come to their own conclusion. In my opinion, in this country our mindset far too often to follow what someone we think is trustworthy says without questioning them. No one is beyond criticism, including me, and we need to question our chosen overlords more often than we do. We have a serious media problem in this country where misinformation and lies are rife and I believe the mindset we as a people have do no favours for this. Not to sound like I'm leading any credence to conspiracy theories and the like, I'm not and most conspiracy theories are if anything born from this problem, and climate science is very much settled in that human activity is causing rapid warming, but misinformation is absolutely rife about this and many other science-related concepts. I find that we as a population has an extremely poor grasp of science and have low ability to think critically. The state of our media is a reflection of who we are as a population.

Anyway, this has become extremely preachy, so I'll end it there, but the message is the same. If you become well-versed in the science, you will come to the undoubtable conclusion that our climate is warming, but I don't want anyone to just take my word for it. I would rather people come to the conclusion on their own. I am by no means an expert and I can only point anyone in the right direction if they want to learn more.

Not to confuse the point too much, let me make these things clear: Our climate is warming at an aggressive pace, and it's caused by human activity. My point is that I don't want anyone to just take my word, I would like people to do their own research and come to that conclusion by themselves.

Apologies if this has become a bit wishy-washy, it's New Year's Eve, I've had a few beers and I'm just trying to communicate my inner thoughts

My impression is that Hadley cell expansion will be a major factor. Due to the excess heat energy in the system, it's highly unlikely that it would be contained within the current cell parametres.

[al78]

24 minutes ago, January Snowstorm said:

You would wonder if we just stuck with the Met Office long range and forgot looking at the models would we all be much happier. The reality is the models are cropping changing every day beyond 6 or 7 days. Years ago I used to think we had the heads up on the general population with regard to incoming cold. I don't think that anymore because 9 times out of 10 the models get it wrong. Extraordinary in the eve of 2024 that computers still can't forecast the weather beyond a week!!!!! (Something they could do 30 years ago)

Of course the models are going to be wrong frequently at a week or more out, there is little model skill at that lead time because the atmosphere is chaotic. Why would anyone with any knowledge/experience of meteorology and/or forecasting think any different? It is ridiculous the way some people cling onto some model output showing a screaming northerly or easterly over a week out then throw toys out of the pram when it doesn't happen as though its mere existence in one ensemble becomes an entitlement to expect it.

[Don]

20 minutes ago, MP-R said:

Doesn’t matter. March onwards is spring. No need to ruin that season too just because the previous one couldn’t get its act on!

Let’s wait until end of February

[CryoraptorA303]

31 minutes ago, Derecho said:

I agree with large parts of your post (I also don't think the AMOC will collapse) but it is slowing down.

Warning of a forthcoming collapse of the Atlantic meridional overturning circulation

WWW.NATURE.COM

---

The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system. Here, data-driven estimators for the time of tipping predict a potential AMOC collapse mid-century...

However the impacts of a notable slowdown could be quite dramatic. I did my postgrad at the Oceanography Centre and it was the big research topic given what happened in 2010. I didn't look at that particular topic (I was looking at how atmospheric circulation had an impact on marine temperatures) but I know people who did.

Given atmospheric circulation has a big impact on local temperatures, a slowdown of the AMOC would have big impacts. 2010 was potentially an interesting instance. There is a lot of unknowns about earlier decades, the RAPID array which monitors the AMOC at 26N was only set up in 2004.

Of course climate change will add more heat into the atmosphere but how that additional heat is distributed depends on what atmospheric circulation does. The below figure is interesting but it's run in a scenario where:

- There is a full collapse
- The model is run without consideration of GhG impacts from the point of initiation

Global and European climate impacts of a slowdown of the AMOC in a high resolution GCM

LINK.SPRINGER.COM

---

The impacts of a hypothetical slowdown in the Atlantic Meridional Overturning Circulation (AMOC) are assessed in a state-of-the-art global climate model (HadGEM3), with particular emphasis on Europe. This is...

The UK climate would cool substantially but much of this would be caused by colder winters with summers as you say becoming hotter. Overall there'd be a slight negative feedback on global temperatures with substantial cooling in the northern hemisphere but accelerated warming in the southern hemisphere.

Of course the big unknown would be the impacts of climate change on top of the above simulation. There is also a big difference between a slowdown and collapse.

A lot of unknowns but a very interesting topic that I'd throw my thoughts in.

Thanks for this addition. It appears I underestimated the full cooling that would occur, although I was essentially correct in the climate of Europe undergoing significant continentalisation, which means colder winters but also much warmer summers. A little known fact is the various latitudes of North America actually have lower average annual temperatures vs Europe due to the colder, more continental winters, despite the very warm to very hot summers.

As you mention, this does not include the warming caused by climate change which will accelerate over time, and I suspect by the time this could be possible, we have already warmed by several degrees and any overall cooling has already long since been cancelled out. As you also mention, a slowdown is very different from a full collapse and I imagine the impact temperature wise is heavily negated with "just" a significant slowdown vs full collapse.

Of course, AMOC has existed for as long as the Drake passage and has survived several slowdowns before rebounding. Eventually the Arctic will either stop melting or melt entirely and stop leaching cold freshwater into the north Atlantic and AMOC will reestablish itself, reversing any of the experienced effects. In the Younger Dryas I believe this happened over the course of about 500 years or so.

Another little-discussed point, I wonder how much increasing ocean temperatures in general will actually strenghen AMOC, considering warmer oceans worldwide means more heat is circulated in AMOC, and how much this could act as a counter to a collapse? As the geologically rapid warming is causing a huge warming of the oceans, and at the same time is causing a melt of the Greenlandic ice sheet, which then leaches cold freshwater into the north Atlantic, this will increase the gradient between hot and cold, and surely this would cause the circulation to strengthen? In winter the gradient between hot and cold is stronger and this generally leads to a stronger Jet Stream in the winter. I'm assuming the same principal would apply? Which in my mind puts into doubt how much AMOC could actually slow down, let alone collapse, vs Younger Dryas where the warming was extremely gradual and the flash flood of fresh, cold water into the Atlantic completely overwhelmed any other signal and led to a significant disruption of the circulation.

Edited December 31, 2023 by CryoraptorA303

[raz.org.rain]

19 minutes ago, Derecho said:

I agree with large parts of your post (I also don't think the AMOC will collapse) but it is slowing down.

Warning of a forthcoming collapse of the Atlantic meridional overturning circulation

WWW.NATURE.COM

---

The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system. Here, data-driven estimators for the time of tipping predict a potential AMOC collapse mid-century...

However the impacts of a notable slowdown could be quite dramatic. I did my postgrad at the Oceanography Centre and it was the big research topic given what happened in 2010. I didn't look at that particular topic (I was looking at how atmospheric circulation had an impact on marine temperatures) but I know people who did.

Given atmospheric circulation has a big impact on local temperatures, a slowdown of the AMOC would have big impacts. 2010 was potentially an interesting instance. There is a lot of unknowns about earlier decades, the RAPID array which monitors the AMOC at 26N was only set up in 2004.

Of course climate change will add more heat into the atmosphere but how that additional heat is distributed depends on what atmospheric circulation does. The below figure is interesting but it's run in a scenario where:

- There is a full collapse
- The model is run without consideration of GhG impacts from the point of initiation

Global and European climate impacts of a slowdown of the AMOC in a high resolution GCM

LINK.SPRINGER.COM

---

The impacts of a hypothetical slowdown in the Atlantic Meridional Overturning Circulation (AMOC) are assessed in a state-of-the-art global climate model (HadGEM3), with particular emphasis on Europe. This is...

The UK climate would cool substantially but much of this would be caused by colder winters with summers as you say becoming hotter. Overall there'd be a slight negative feedback on global temperatures with substantial cooling in the northern hemisphere but accelerated warming in the southern hemisphere.

Of course the big unknown would be the impacts of climate change on top of the above simulation. There is also a big difference between a slowdown and collapse.

A lot of unknowns but a very interesting topic that I'd throw my thoughts in.

I feel that the issue is the discrepancies. 
 

The AMOC has observed a notable slowdown but that's also proportional to the rate of accelerated warming observed in Europe. There's also a direct link between the observed cooling of the North Atlantic and persistent atmospheric blocking across Europe resulting in extreme and prolonged heat. Schenk et al. 2018 have discussed this effect and theorise the same feedback happened during the Younger Dryas.

But I believe that may be the issue when discussing paleoclimatology. Most if not all of our modelling and reconstruction techniques are conducted using proxy data samples from previous periods of non-comparable conditions. The Younger Dryas seems to be the benchmark for climatology when discussing the impacts of AMOC strength, but no one seems to be accounting for the fact that the Younger Dryas saw significant continental glaciers in North America (Laurentide) and Scandinavia (Fennoscandinavian). Of course an AMOC decline would result in widespread cooling given these features, the AMOC was effectively preventing further glacial encroachment. Those features are non-existent now outside of Greenland, whose geography keeps it self-contained. However, 2023 has thrown another oddity into the mix with the effects of termination shock. We got a good demonstration of how oceanography responds to anthropogenic influence.

I would say that the principle contribution of the AMOC in the modern climate is precipitation patterns, to be honest. Further AMOC slowdown or hypothetical collapse would be contending with the potent effects of accelerated warming. I often bring myself to question how much of a cooling effect would even be observed during the winter months, given what we're currently observing in Canada and the US and the vastly reduced cooling capacity of the Arctic. Summers would most certainly get very dry and hot due to aforementioned Hadley cell expansion and near absence of precipitation creating arid conditions.

[Chasbrown]

12 minutes ago, al78 said:

Of course the models are going to be wrong frequently at a week or more out, there is little model skill at that lead time because the atmosphere is chaotic. Why would anyone with any knowledge/experience of meteorology and/or forecasting think any different? It is ridiculous the way some people cling onto some model output showing a screaming northerly or easterly over a week out then throw toys out of the pram when it doesn't happen as though its mere existence in one ensemble becomes an entitlement to expect it.

Begs the question why bother looking at the models?!

[raz.org.rain]

19 minutes ago, CryoraptorA303 said:

Thanks for this addition. It appears I underestimated the full cooling that would occur, although I was essentially correct in the climate of Europe undergoing significant continentalisation, which means colder winters but also much warmer summers. A little known fact is the various latitudes of North America actually have lower average annual temperatures vs Europe due to the colder, more continental winters, despite the very warm to very hot summers.

As you mention, this does not include the warming caused by climate change which will accelerate over time, and I suspect by the time this could be possible, we have already warmed by several degrees and any overall cooling has already long since been cancelled out. As you also mention, a slowdown is very different from a full collapse and I imagine the impact temperature wise is heavily negated with "just" a significant slowdown vs full collapse.

Of course, AMOC has existed for as long as the Drake passage and has survived several slowdowns before rebounding. Eventually the Arctic will either stop melting or melt entirely and stop leaching cold freshwater into the north Atlantic and AMOC will reestablish itself, reversing any of the experienced effects. In the Younger Dryas I believe this happened over the course of about 500 years or so.

Another little-discussed point, I wonder how much increasing ocean temperatures in general will actually strenghen AMOC, considering warmer oceans worldwide means more heat is circulated in AMOC, and how much this could act as a counter to a collapse? As the geologically rapid warming is causing a huge warming of the oceans, and at the same time is causing a melt of the Greenlandic ice sheet, which then leaches cold freshwater into the north Atlantic, this will increase the gradient between hot and cold, and surely this would cause the circulation to strengthen? In winter the gradient between hot and cold is stronger and this generally leads to a stronger Jet Stream in the winter. I'm assuming the same principal would apply? Which in my mind puts into doubt how much AMOC could actually slow down, let alone collapse, vs Younger Dryas where the warming was extremely gradual and the flash flood of fresh, cold water into the Atlantic completely overwhelmed any other signal and led to a significant disruption of the circulation.

Latitude comparison is often not a great method to be fair. North America will achieve considerably colder winters due to the continentality bias. There's a video on YouTube that does a good job of explaining this, and explains why such extremes generally don't exist in the southern hemisphere. North America has an unfortunate (or fortunate) combination of factors; large amount of landmass found to the north in the Arctic, favouring the development and southward progression of cold air masses, a large mountain range (the Rockies) disturbing the warming effect of moist westerlies before they can progress across the continent, and a self perpetuating reserve of cold in the Hudson Bay and Canadian Shield.

Meanwhile in Europe, we're mostly surrounded by open oceans. The continentality has a large southerly bias with the arid Sahara and salty Mediterranean to the south. Basically, I don't think Europe has the geography for observing extreme prolonged cold, especially not southern or Western Europe. The only reason it has happened in previous times is due to the presence of significant continental glaciers (among other variables).

 

Edit: Should mention that European Russia does often see extreme cold develop. The geography of Russia is comparable to North America and allows for extreme cold to build. Traditionally this would progress into Eastern Europe on occasion, but I believe this is becoming a rarer occurrence.

Edited December 31, 2023 by raz.org.rain

[CryoraptorA303]

4 minutes ago, raz.org.rain said:

Meanwhile in Europe, we're mostly surrounded by open oceans. The continentality has a large southerly bias with the arid Sahara and salty Mediterranean to the south. Basically, I don't think Europe has the geography for observing extreme cold. The only reason it has happened in previous times is due to the presence of significant continental glaciers (among other variables).

Neither do I. I only mean it'll become more continental in the sense that winters will be as cold as today or somewhat colder, while summers will be hotter, and we will be drier year round. The continental classification will expand westward. I doubt anywhere in the UK would actually fall under that classification, if anything the far east would become steppic and the south coast mediterranean.

[Metwatch]

10 minutes ago, Chasbrown said:

Begs the question why bother looking at the models?!

To have a laugh

[raz.org.rain]

11 minutes ago, CryoraptorA303 said:

Neither do I. I only mean it'll become more continental in the sense that winters will be as cold as today or somewhat colder, while summers will be hotter, and we will be drier year round. The continental classification will expand westward. I doubt anywhere in the UK would actually fall under that classification, if anything the far east would become steppic and the south coast mediterranean.

That seems to be the logical progression really. Hypothetically, by the end of the century, a net cooldown of the winter period would result in winters becoming comparatively colder. I'll stick my neck out on the line and assume that winters will be significantly warmer by then and we'll be acclimatised to that fact, so reverting back to the winters we have at present will seem like a notable cooldown. Summers would get hotter and drier, of course. I believe that seasonal extreme in difference will be the fatal detail.

 

Edit: Funnily enough, it only feels like a recent trend for climate change factors to be cross compared and accounted for as hypothetical events that could occur concurrently. It's astounding how often you'll see academic discourse fail to account for the progression of other climate change factors in parallel to their hypothesis. I say this as a postgraduate who understands the restraints of academic research. For the most part it's exceedingly difficult to consider the variables of variables, particularly if those variables are already hypotheticals themselves. For example, methane release and termination shock have only recently been considered as potentially potent factors.

 

Anyway I'll stop there, I'm just rambling at this point!

Edited December 31, 2023 by raz.org.rain