Climate Change and the Next Glacial Period
In this thread, I'm going to lay out in detail why scientists believe the climate is likely headed toward reglaciation, and how this bears on the issue of climate change.
We'll be discussing the long range modeling of the question and why it's hard to get definitive answers.
First stop will be the basic idea of an ice age and how the idea has changed over the years.
We'll be discussing the long range modeling of the question and why it's hard to get definitive answers.
First stop will be the basic idea of an ice age and how the idea has changed over the years.
Comments (157)
We now know that those four "ice ages" were glacial periods in a larger scale climate event. The climate swings back and forth between long glacial periods and short interglacials.
It looks like this:
I think you are taking the chart for granted without examining some of its detail. First, all statistics represent some view of the past, and the past does not in any way guarantee the future. That is because an assumption of necessary continuity is speculative on your part and is without either logical or scientific support. To see this, one must realize that one or more causative factors for the behavior of that chart could abruptly come into being, disappear, or change without prior notice, as for example by a large asteroid strike.
Second, we must look at the time scale on the horizontal line. In the long run it may continue fluctuating, but on shorter term we will not be around to check where the chart is headed.
The relevant changed causative factor for the present appears to be the alarming uncontrolled spread of limited intelligence monkey relatives all over earth whose powerful political leadership is unable to see the negative side of rapidly increasing technology which is about to destroy their niche for survival on this planet. The environment can be very fragile -- that chart has and will possibly change very rapidly again. What is does say is that if an ice age is coming it will happen shockingly rapidly, perhaps a decade or less, due to run-away circumstances, like that large asteroid strike.
Global warming has become obviously real in the past decades. The Earth might not mind a few more degrees. But we will all die of starvation if not by nuclear wars or rapid unchecked pandemics.
That chart shows the past in the absence of human interference, and it will resume its gyrations after all humans are gone. In other words, it may be great science but it could be totally irrelevant to our present concerns.
Fair warning.
:cool: Have you come across any video/audio clips on how straight A students work for/under the C/D/even F students? :snicker:
Oppenheimer (A-bomb) was far, far brainier than Roosevelt (WW2 prez). Think of that the next time you see a moron/idiot/fool (like me)! Not saying "dumb animals!" from now on. I could be bloody well working (my ass off) for 'em! :snicker:
:lol:
Assuming no mega-colossal supereruptions will happen. (Last one was I guess about 75 000 years ago, which created an ice age for us humans.)
Cool. So let's look at the science behind this. How could you object to that?
So different people are using the term "ice age" in different ways.
That's a frigging long, long waiting time. How many human generations are we looking at here? If anything wonderful/fantabulous is on the cards (for earth, for humans), it's gotta be "around 50k years" from now. Let the countdown begin! We need to get our act together, that's all! Vague but that's all I can muster at the moment!
:up: I've been saying "large scale ice age" to try to specify.
Quoting Agent Smith
We don't really know when the next glacial period will start. What we know is that we're moving into a trigger point now. Reglaciation would start with an increase in the size of the northern glaciers. We know the opposite is happening. But we also know the global oceanic heat conveyor is slowing down (due to global warming). If it stopped, the climate would plunge into an event like the Younger Dryas. That would probably be followed by a long glacial period. So ironically, increased CO2 could trigger reglaciation.
But let's get back to basics. Next up: what is a large scale ice age?
What is this "trigger point" you keep talking about? Is it a solar change, something to do with the sun's magnetic field, causing reduced energy from the sun? The sun's magnetic field is not well understood:
https://www.space.com/why-sun-atmosphere-hotter-than-surface
@Tate is pulling it out of his rear end. This is CC denial, hidden behind yet another mask.
It has to do with the shape of the Earth's orbit. Sometimes the orbit is more circular, sometimes elliptical. When it's elliptical, the Northern Hemisphere summers are cooler. When this happens, per theory, ice which formed in the winter doesn't get enough heat to melt, and so it keeps growing. Ice reflects heat back out to space, so increased glaciation is associated with positive feedback. This explains why reglaciation is always so abrupt.
What do you think causes the shape of earth's orbit to abruptly change?
It doesn't.
These graphics and tables will give an idea of geological timescales, and allow some orientation if we need to talk about 'snowball earth' previous extinction events or whatever.
Then, we can look at https://en.wikipedia.org/wiki/Milankovitch_cycles There are 3 cycles that interact with different periods: precession, obliquity and eccentricity. (This is still a simplification as the link makes clear.)
Quoting Tate
Do you mean looking at ice cores? Looking at rocks would involve much longer timescales.
https://en.wikipedia.org/wiki/Last_Glacial_Period
Assuming you are talking about the cycles of the Quaternary glaciation, we need to consider This:
Perhaps you can shed some light on that?
My takeaway thus far though is to notice that the change in climate we are now undergoing has been man-made in a couple of centuries, and for us to have noticed the effect so very quickly suggests that it dwarfs the effect of the Milankovitch cycles. Looking at the larger history of earth climate, one sees such huge variations that it seems clear that earth climate is a complex system with many semi-stable attractors. This is the worry that climate scientists have, that our CO2 emissions can move the earth from its current glacial/interglacial cycling to a permanently different semi stable cycling.
Quoting Tate
Does this M.I.T. Technology review article jibe with what you are reading?
cyclic gravitational tugs from Jupiter and Saturn periodically elongate Earths orbit, and this effect combines from time to time with slow changes in the direction and degree of Earths tilt that are caused by the gravity of our large moon. Consequently, summer sunlight around the poles is reduced, and high-latitude regions such as Alaska, northern Canada, and Siberia turn cold enough to preserve snow year-round. This constant snow cover reflects a great deal of sunlight, cooling things down even more, and a new ice age begins. Naturally, this process does not occur with anything like the speed portrayed in the movie The Day After Tomorrow, but geological and other evidence shows that its happened at least four times.
In about 2,000 years, when the types of planetary motions that can induce polar cooling start to coincide again, the current warming trend will be a distant memory.This means that humanity will be hit by a one-two punch the likes of which we have never seen. Nature is as unforgiving to men as it was to dinosaurs; advanced civilization will not survive unless we develop energy sources that curb the carbon emissions heating the planet today and help us fend off the cold when the ice age comes.
(F. Hadley Cocks,Duke U. Prof of Mechanical Engineering and Materials Science)
Enquiring is a-okay. Lying is not.
My plan is to take it slow. I've dragged out the old textbook. My plan is to do an overview of historical geography, and then start examining articles.
Quoting unenlightened
I'm familiar with the 100,000 year problem. We'll get to it.
Quoting unenlightened
I was talking about the original conception of ice ages. The word "quaternary" refers to the idea that there were four ice ages in the past. We now call those glacial periods.
Quoting unenlightened
I've wondered about this question for a long time. I was really happy to see scientists creating models to try to answer it. It seems that every year more advances are made, so let's look at some of those advances!
I think it's possible that the stress will divide our species between civilized and those who lose skills and devolve. That may sound bizarre, but it's easy to forget that our gigantic population of close relatives is unusual for organisms like us. Splitting would be kind of normal.
Have you read that whole article?
Yes, I did. It makes one appreciate that from
the planets point of view ( as opposed to human civilization), the time scale of climate change will be barely noticeable compared with that of the next ice age.
True.
Quoting Tate
"Abrupt" was your word.
Quoting Tate
Reglaciation is usually abrupt because once it starts there are positive feedback loops that reinforce it. The trigger points just happen from time to time. They're caused by changes in the circularity of the Earth's orbit.
Whether the abrupt shift to reglaciation happens depends on a number of factors, which is why they try to model it with computers, to account for all the variables. I say "all" the variables, but some are hard to account for, so all climate models carry some degree of uncertainty.
Someone mentioned this in the other thread and it bears repeating: climatology is a science that requires getting used to a lot of unknowns. When will reglaciation start?
We really don't know.
What I asked about was the cause of the changes in Earth's orbit. @Joshs gave somewhat of answer, referring to the gravity of other planets, but I do not see how this could really be the case. We just had a major alignment of planets, but I didn't hear anything about that changing the orbit of the earth.
Quoting Tate
I really would not call this sort of climatology a "science". It's pure speculation without any experimental evidence. I asked about how the magnetic field of the sun affects the climate of the earth, because the sun is known to be the major influencer of earth's surface temperature. But scientists appear to have little if any understanding of this magnetic field, or fields. How can long range climatology be a "science" when the activities of the thing which has the greatest influence on it, the sun, is not at all understood?
:smile:
The administrator will quickly take you out into the woods and before you know it...BANNED!!!
(Or something like that, eh?)
I'm not sure what you're referring to. The sun's electromagnetic field is polarized like the Earth's. It doesn't extend too far into space. It doesn't reach Mercury, much less the Earth.
Are you talking about solar winds?
:rofl: C'est la vie! :up:
These fluctuations in climate are not cyclical like the the first graph I posted, which showed a parade of interglacials. This graph shows the dramatic change that one little lifeform called cyanobacteria caused, almost resulting in the final mass extinction due to the loss of atmospheric CO2.
The whole globe was covered in ice. It shows the results of massive emissions of CO2 caused by volcanoes, which caused equatorial waters to steam and put palm trees on the poles. It's a fascinating saga.
At the bottom of the graph you see four purple blocks representing events that some geologists call ice ages. it doesn't really matter what we call these larger scale cold spells. The point is: we're in one.
Quoting Tate
It bloody well does matter what we call them. You really need to stop waving "ice ages" about quite so carelessly. Do you not see how confusing you are making it for anyone reading the thread? I assume you are clear that the 4 ice ages you were talking about on page one don't even add up to the last of the 4 ice ages you are now talking about, because the quaternary period only covers the last 3 million years approx and just the last "cold spell" in your graph above covers 50 million years. But you certainly do not make it clear to the reader.
Sorry. Michael had already posted a blurb about how geologists call those larger scale cold events "ice ages", while in the public domain that term means woolly mammoths and saber tooth tigers, in other words, the last glacial episode.
I responded to him that I've been compromising by calling them "large scale ice ages."
Do you have advice for how to make it clearer?
Well I put up links to help folks with terminology and timelines, and numbers of years ago are really useful for sorting things.
Quoting Tate
But the Cambrian explosion started about 539 million years ago, so the first glaciation period in your graph is not a snowball earth event but the Late Ordovician glaciation and the whole globe was not covered in ice.
Quoting Tate
Here you are unequivocally muddled; the cyanobacteria began photosynthesis about 3.5 Billion years ago and the oxygenation of the atmosphere about 2 billion years ago.
https://en.wikipedia.org/wiki/Great_Oxidation_Event
Which means that before about 2 billion years ago iron rust was green but after that it became reddish. Should that colors be called greed or redeen?
My goal is to get to articles. I think what you are telling me is that you want more depth. Would you like reading homework? Or excellent and trustworthy PBS documentaries? (it's called Eons, and it's great) Or do you want to talk about something specific? The cyanobacteria?
I'm figuring you and I are the only ones reading this, so let's do it our way.
The times were on the graphs.
From here:
"For cyanobacteria to trigger the rapid onset of a Snowball Earth, they must have had an ample supply of key nutrients like phosphorous and iron. Nutrient availability is why cyanobacterial blooms occur today in regions with heavy agricultural runoff.
"Fortunately for the bacteria, Earth 2.3 billion years ago had already entered a moderately cold period, reflected in glacially formed rocks in Canada. Measurements of the magnetization of these Canadian rocks, which the Caltech group published earlier this year, indicate that the glaciers that formed them may have been at middle latitudes, just like the glaciers of the last ice age.
"The action of the glaciers, grinding continental material into powder and carrying it into the oceans, would have made the oceans rich in nutrients. Once cyanobacteria evolved this new oxygen-releasing ability, they could feast on this cornucopia, turning an ordinary glaciation into a global one.
"Their greater range should have allowed the cyanobacteria to come to dominate life on Earth quickly and start releasing large amounts of oxygen," Kopp says.
"This was bad for the climate because the oxygen destabilized the methane greenhouse. Kopp and Kirschvink's model shows that the greenhouse may have been destroyed in as little as 100,000 years, but almost certainly was eliminated within several million years of the cyanobacteria's evolution into an oxygen-generating organism. Without the methane greenhouse, global temperatures plummeted to -50 degrees Celsius."
There's another theory that snowball earth was caused by the break up of Rodinia which exposed basalt which absorbed CO2 and released sulfur which causes cooling.
The cyanobacteria story is more poetic, though.
Your attitude is unwarranted. By and large, everything I've said is true. If I happen to get facts muddled, I'm still well-meaning and don't deserve the scorn level you've been generating.
If you don't want to contribute meaningfully to my thread, could you at least go elsewhere?
The point was that radiant heat from the sun has the biggest influence over the earth's surface temperatures, and scientists seem to know very little about the sun's capacity to radiate heat. I suppose I'm off topic, and we need a different thread about the sun's influence on the earth's climate.
It is the biggest influence. Easily overlooked, you're right. There's the grand solar minimum (solar minimum) that some say started two years ago and will cause cooling until around 2050? I don't know much about.
I took the liberty of copying your comment here because the other thread is closed.
My response is this:
From Ice Age, Interrupted article link
Note that while the man-made CO2 certainly has interrupted the trajectory of the climate change, it did not, and could not destroy the insolation changes that are responsible for the ice ages. Also note that this article uses the words "metronome" and "pace maker" as an analogy to the functioning of isolation changes. I'm sure you get the point.
The point I get is that natural insolation will not be cancelling the impacts of man-made global warming. Another point is in the tittle: ice age, interrupted. Compare with:
So your article agrees with me, or rather, my take on CC is far closer to current science than Tate's crypto-denialism.
As for metronomes... sometimes they break. Gime a sledgehammer and a metronome, and I'll show you how it might happen. The metronome is our climate, the sledgehammer is greenhouse gases.
We have solar cycles, about which not much is known over the long term, because the records cannot be read through the inferred influences of the atmosphere. We know that solar radiation varies with the eleven year sunspot cycle, and another 100 year cycle, and we infer from. We also know from astronomical study of main sequence stars, that the sun is getting hotter, by about 25% over 3billion years or so.
Insolation of Earth is further modified by Milankovitch cycles. These have periods of 26000, 41,000, and 100,000 yrs. The reason why the North polar region is the influential one for these cycles is that most of the land mass is in the Northern hemisphere and the land heats and cools more quickly than the sea, and ice forms more easily on land, because sea has salt as antifreeze. So the Antarctic is more stable.
The temperature of Earth's surface is produced by insolation modified by transparency and insulation effects of the atmosphere, and the reflectivity of the surface itself, and by the absorption of heat by photosynthesis. (Forests also have a large cooling influence through transpiration and associated cloud production.)
The lesson I take from the 2 billion yr old story of cyanobacteria poisoning the atmosphere with oxygen and producing a snowball Earth, which might have remained stable until the present because of the reflectivity of ice, but for some vulcanism restoring a bit of CO2 and maybe darkening the ice a bit with ash, is that the Gaia hypothesis is not true. The living planet is not self regulating.
Rather, there have been wild fluctuations of climate through geological time far larger than can be accounted for by variations of insolation. The history of humanity has been one of unusual climate stability sufficiently long for the effects of milankovitch cycles to become noticeable.
When Prime Minister Harold Macmillan was asked what was the greatest challenge for a statesman, he replied: 'Events, dear boy, events'.
Vulcanism, asteroids, continental drift, and changes to the biome. Human civilisation is a change to the biome that has affected every region and every species. It is events that destabilise the climate and send it careering off to a heating or cooling until it arrives at a new semi-stable climate maybe tens of degrees hotter or cooler. This happens because of positive feedback and tipping points, which complex systems analysts will be familiar with.
:rofl:
One man's food is another man's poison, oui monsieur?
Life has a dark history - we need to deep-six this investigative, detective mentality lest we discover the awful truth behind our so-called evolutionary success, our bloodlust to put it mildly.
For some reason being alive doesn't make me as happy as it used to!
:up:
:up: :up: :up: :up:
The standard, observed sunspot cycle is approximately eleven years, we are heading into a maximum period right now.
At the minimum period, the sun's magnetic field is an organized dipolar field, extending far into interplanetary space. The dipolar field allows particles to move rapidly along field lines, and this is the solar wind. The earth, being currently on a different plane is not exposed to this rapid solar wind of the minimum period.
At the maximum period, the magnetic field breaks down, and is randomized. This allows more random coronal ejections of particles, in random directions, in a slower solar wind. Some of these solar flares may be directed toward the earth.
When the magnetic field reestablishes itself as dipolar, at the next minimum period, it has reversed polarity from the last minimum period. So the entire cycle, to return to the same polarity, is approximately twenty two years.
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/solar-magnetic-field#:~:text=The%20solar%20magnetic%20field%20is%20highly%20variable%2C%20which%20makes%20the,like%20that%20of%20the%20earth.
https://earthsky.org/earth/magnetic-north-rapid-drift-blobs-flux/
You are losing track of the relative time scales here. The history of humanity is a point on the geological timescale. We could be living right smack in the middle of one of those "wild fluctuations of climate" that you mentioned and not notice it.
Not always. This interglacial started with an abrupt change called the Younger Dryas. We would notice if that happened. A shutdown of the oceanic heat conveyor is believed to have caused it and scientists are watching that current now because it's slowing down due to global warming.
Perhaps I wasn't clear. The history of humanity spans roughly the Quaternary period, which consists of alternating glaciations and interglacials over the last 3 million years or so; the beginning of the stone age is a little further back into the Pliocene Epoch. That is what I call a period of stability relative to the much larger climate variations over geological time. Note that i call the mere covering of Northern Europe and Canada with an ice sheet benign stability in the context of major disruptive events.
Why don't we look at some of the research behind this:
Quoting unenlightened
Specifically, let's look at the support for this Wikipedia statement in it's article entitled "Ice Ages":
"The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted to prevent the next glacial period for the next 500,000 years, which otherwise would begin in around 50,000 years, and likely more glacial cycles after.[4][5][6]"
I have university access to scientific papers today, so I'll print out the articles referenced by the Wikipedia article and we can discuss them. Sound good?
Live Science
This is a report on a computer model. The article states:
"Even if we burn only a quarter of the Earth's total reserves of fossil fuels (currently we have burned less than one tenth of reserves), the carbon dioxide remaining in the atmosphere could cause the next ice age to be skipped because ice sheets and glaciers will have melted and won't be able to reform substantially, Tyrrell found."
"In fact, burning up all of Earth's reserves would prevent the next five ice ages, the model shows, he said."
So one of the problems with Wikipedia's article is
"The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted..."
What amount? The amount we've emitted so far? No. That amount is not predicted to cause a miss of coming glacial triggers.
Burning all the fuel we can access probably would, as I've previously noted, twice.
No one says the insolation will cancel the man-made global warming. But neither does the man-made global warming stop everything and prevent the earth from entering the ice age period.
And no, the article does not agree with your assessment that the man-made CO2 will end the ice age. "Interruption" means there is the change in downward trajectory of the climate temperature because the CO2 produced by industrialization is increasing the temperature. But it cannot go on indefinitely so as to stop the glacial cycle.
Quoting Olivier5
It's good to insert what-if scenarios, but let's deal with what's real right now. It's not broken yet, let's deal with that.
"Global Warming Good News: No More Ice Ages"
I cannot comment on the computer model, but my argument is that this is very very bad news, not good news.
I have already pointed out that Earth has been in a fluctuating ice period for 33 million years. A world without ice is going to be a totally unrecognisable place. Covering Northern Europe and Canada with ice would happen very slowly and would not disrupt the whole world to anything like the same extent.
Quoting unenlightened
That title was click bait. The article was supposed support this statement:
"The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted to prevent the next glacial period for the next 500,000 years, which otherwise would begin in around 50,000 years..."
Firstly, the Wikipedia statement doesn't even make sense. Secondly, the cited articles don't support it. That Wikipedia article is going to be edited.
Ya think?
I don't see why not.
Icebergs. That's why. Icebergs breaking away and migrating farther to other oceans and melting, causing changes in oceanic patterns which then causes the oceans to absorb excess CO2 from the atmosphere. The resulting cooling effect triggers the ice age.
Take away: when oceans temperature lowers, more CO2 are absorbed into the oceans.
We the planet should be so lucky to re-glaciate, preferably before the 2024 election.
I think you are telling yourself fairy tales, perhaps because you are too afraid to face the truth. At current melt rate the northern hemisphere won't have any permanent ice by 2040, 2050 at the latest.
"Sea ice" you should say; Greenland ice will take a little longer to melt, fortunately.
Quoting Tate
I'm all for editing articles, and I agree the sentence is wooly and inaccurate, and at the same time too precise about the future which remains open to an extent. But wiki is better than clickbait.
That's correct. Thanks for the precision.
That click bait article was referred to by the Wiki article.
I'll be using a range of articles from scientific publications.
It's going to be a shit show. I agree.
Ah. Apologies; since you had just said that, I thought that it was one of your articles.
No. I was just killing two birds with one stone: contributing to this topic and preparing to edit a poorly written Wikipedia page. That page used sources that misquoted other sources. Not good.
If you want, we could talk a little bit about the present major ice age, sometimes called the Quaternary. We can discuss theories about why it happened. The Wikipedia articles for that are pretty good, so I'll reference them.
To review:
Major ice ages, as we discussed, happen for a variety of reasons.
In the case of the Quaternary, for some time now the leading theory has been about a change in ocean currents which happened about two and a half million years ago. It is true that atmospheric CO2 is down about 90% from what it was before the Quaternary, but that may be a positive reinforcing side effect as opposed to a cause. Cold water holds more CO2 than warm water, so as the ocean currents changed to cool the surface, the oceans started pulling in CO2, cooling the world further.
From here:
An important component in the development of long-term ice ages is the positions of the continents.[16] These can control the circulation of the oceans and the atmosphere, affecting how ocean currents carry heat to high latitudes. Throughout most of geologic time, the North Pole appears to have been in a broad, open ocean that allowed major ocean currents to move unabated. Equatorial waters flowed into the polar regions, warming them. This produced mild, uniform climates that persisted throughout most of geologic time.
"But during the Cenozoic Era, the large North American and South American continental plates drifted westward from the Eurasian plate. This interlocked with the development of the Atlantic Ocean, running northsouth, with the North Pole in the small, nearly landlocked basin of the Arctic Ocean. The Drake passage opened 33.9 million years ago (the Eocene-Oligocene transition), severing Antarctica from South America. The Antarctic Circumpolar Current could then flow through it, isolating Antarctica from warm waters and triggering the formation of its huge ice sheets. The Isthmus of Panama developed at a convergent plate margin about 2.6 million years ago, and further separated oceanic circulation, closing the last strait, outside the polar regions, that had connected the Pacific and Atlantic Oceans.[17] This increased poleward salt and heat transport, strengthening the North Atlantic thermohaline circulation, which supplied enough moisture to arctic latitudes to create the northern glaciation.[18]"
I'm not gonna ask for source on this. I'm not concerned about sources. I'm more concerned about the logic of what you're saying. If icebergs are breaking away from the ice sheet, then they are mobile. If they're mobile, they're drifting to the other oceans. And if they're going to those oceans, then they are cooling those oceans, like the Atlantic. Which is what we need to happen so the oceans can absorb CO2. The ice need to migrate to faraway oceans, and not just stay in the antarctic. The arctic apparently is enclosed, trapping its ice.
So then, the absorption of excess CO2 will allow the natural processes of insolation changes, which would trigger the start of glacial event or the ice age.
Of course this makes sense only if the rising CO[sub]2[/sub] levels don't cause a paradoxical reaction and hasten/sustain/intensify/prolong an ice age.
Actually the OP doesn't say that at all.
I read between the lines! Perhaps an overactive imagination. Apologies, I'm into conspiracy theories! :blush:
Let's not do that, ok?
Roger!
I don't know, this thread has not gone anywhere in millions of years of discussion. Maybe a good conspiracy theory could liven it up a bit.
This is a weekend project for me.
Get back to work then! It's not the weekend yet.
:grin:
This seems to me to be fundamental to the relative coolness of our climate ever since. In the North, the ice sheets come and go, but the Antarctic has been much more stable. But things are changing.
https://www.nationalgeographic.com/environment/article/antarcticas-ice-could-cross-this-scary-threshold-within-40-years
Here are links from that article to a couple of papers available to the public.
https://www.nature.com/articles/s41586-021-03427-0.epdf?sharing_token=twBZA98km78OTx6AMy9W3dRgN0jAjWel9jnR3ZoTv0O1wLV2jblnuB2ZPB-nrPqiYIGrpSsWrxM6Zs9mXF_ynlXr1wSaMYX_yu3g0MtdOLlXhPdfZT7AIzZxxZPZi3eUhpkHsGguFotFouKQ8B8w2uIC2vXVZ2u18y_S1IFK1j1eEHc3lS8clGR4m-3cQS-WfAfUH5RhB-WU5xv6HTwn7ITa6h-rNuY7QaoyU5Ywu48%3D&tracking_referrer=www.nationalgeographic.com
https://www.nature.com/articles/s41586-021-03302-y.epdf?sharing_token=U2E-t2XStTtmBYyTQ7DPQdRgN0jAjWel9jnR3ZoTv0NBHKcAC_lrDjYnFOA0lhyL19H0suFTY3jD1u_wNHSNLuEPeFiQcKfrHUjiWydOqBabgwjyVi_e3JBCqopJDL-a4vTPRx8BISM-mI4eZrD-0dOT6mF18jZFK6RISo8M7dkEgurfH5a6tZ2nrBje9JYKnkjGDKrByRsfxgfGndjjnH1Jgqhn5nmt93q5gR3_Hgw%3D&tracking_referrer=www.nationalgeographic.com
I wonder if the tipping point they're talking about is where the loss of Antarctica's albedo effect causes positive feedback on warming. Once that starts, there's no easy way to go backward. It would cause a gigantic global refugee crisis and crop failures at the same time.
I'll dig into it. Thank you!
I think they are not sure. There are several positive feedback mechanisms, and some negative ones. The albedo is one, and the loss of sea ice can also speed up glacier flow rate. But also, warming seas increase snowfall. The one they are least sure about is what happens as the ice edge moves back and the exposed edge gets thicker.
The nature of tipping points is that the only way to find them in practice is to tip them. That would not be a great policy, though, however interesting.
This is from the first paper:
"These results demonstrate the possibility that rapid and unstoppable sea-level rise from Antarctica will be triggered if Paris Agreement targets are exceeded."
This is fascinating. They aren't saying Antarctica will give up all its ice, it will just be smaller by 2300. There's little reason to doubt that by 2300, a lot of presently inhabited coastline will be abandoned (unless there's a significant policy change). This was just looking at a 3 degree rise in mean temperature. A high projection is 8 degrees (assuming all available fuel is burned.)
I've been reading about climate models. There are hundreds of short term models. This is the basis of IPCC statements.
Long range models are problematic because of the proportionally larger amount of data and the challenges of testing them.
Since the 1990s, long range modeling has progressed by an accumulation of contributions by scientists. The size of ice sheets is considered to be one of the most important factors, if not the most important.
When reglaciation starts, the first step is an increase in northern ice accumulation. Likewise, deglaciation starts with a decrease in their size.
I've been surprised that it's hard to find good books on long range modeling.
We can draw an example from weather forecasting. The accuracy of the long term forecast is highly dependent on the accuracy of the short term forecast. Consider a seven day forecast. If the first 24-48 hrs. is incorrect, by even a small factor which is somehow missed, this will likely make the later portion completely irrelevant so that it's not even close. But if the first 48 hrs. hold true to the forecast, the later period will likely just need small changes. What this indicates is that a very slight, unforeseen change, in the very near future will render any long term model which does not account for it, completely useless. The closer in time to the beginning point of the forecast period, the unforeseen factor is, the smaller it needs to be, to have a large affect on the accuracy of the long term. This could be like the "trigger point" you referred to earlier.
True. I want to review some articles on long-range forecasting. It's fascinating stuff. I was hinting earlier about why the latest models are better, because they include previous research into how to weight factors.
Then I want to discuss one article on the 100,000 year problem and a startling implication of its proposed solution. If the 100,000 year cycle is a result of a change in ocean currents that further cooled the surface of the earth, this means reglaciation is now being triggered by a shutdown of the oceanic heat conveyor, the very same oceanic current that is slowing now due to global warming. No scientist is predicting a shutdown, but if it did, reglaciation would be triggered.
If nothing else, it's a cautionary tale about being certain of the future of the climate.
The general principles involved in ocean currents can be described. First, the prevailing wind at the equator is from the east, due to the spin of the earth, the air doesn't spin along with the earth fast enough to keep up with the earth, so there is a constant wind from the east. This pushes the warm water at the equator, which is the most heated from the sun, toward the west. It naturally curves away from the equator, to the right in the north, and the left in the south, as the Coriolis effect. So in the northern hemisphere, surface water moves northward along the east coast of the large continents, and southward along the west coast This brings heat toward the poles in a way which is sort of like convection, but the principal source of the wind is the mechanical spinning of the earth, rather than a convective wind. This is important, the principal "weather maker" is the mechanics of a spinning body with oceans and an atmosphere, solar heating and convection are secondary.
The surface currents of the oceans would be a simple process, except the surface water is forced away from the equator by the winds of the spinning body, and there is no such force to bring replacement surface water, from the north and south. That's why it's different from convection which is solely temperature driven. So much of the replacement water, at the equator, has to come from the depths. This creates flows in the depths, and these flows are not well understood. El Nino is known as a slowing of this flow of cold replacement water along the west coast of South America.
You can see that the real cycle is not a flow of surface water, but the cycling of water from the surface to the bottom, and back to the surface. It is very complicated because there are many layers and the layers are not necessarily vertical, as it is a three dimensional activity. We can imagine principles similar to air movement, but on a slower scale, horizontal winds, vertical convections, and the movement of distinct "air masses" (water masses in this case). None of these activities are well understood.
It looks like this:
There's a theory that once we came out of primarily Milankovitch forcing, the 40,000 year cycle, to an orbital forcing cycle of 100,000 years, shutdown of this oceanic heat conveyor became the trigger for reglaciation.
This means the Northern Hemisphere summer insolation minimum isn't the main trigger, it just lowers the threshold. We're in that low threshold period now, and the ocean currents are slowing down due to global warming.
This means the forecast could be worse than just global warming. We could be headed for a period of extreme volatility.
A model known as CLIMBER-2 was created in 2005. It assumes that reglaciation is triggered by a minima in summer insolation in the Northern Hemisphere.
This model predicts an unusually long interglacial even without an increase in pCO2 forcing. With a 5000 Gton increase in CO2, the climate comes out of the glacial/interglacial cycle completely for at least 500,000 years.
One possible answer as to why the model is predicting such a long interglacial (50,000 y) even with baseline pCO2 might be that the so-called Anthropocene didn't start in the 1800s. It might have started with human agriculture as long as 6000 years ago. Here.
That map is extremely vague, just showing some generalities. It's not at all useful for any attempt to determine anomalies. The whole concept of "oceanic heat conveyor", is equally vague, and overly generalized. The oceans are always going to convey heat, so long as the earth is spinning, and the sun is heating, that's what the oceans do. What is at issue, if you are talking about a potential trigger point, is minute peculiarities, and changes to how the oceans convey heat. Since the vast majority of oceanic flow is well below the surface, the information is not available to produce an adequate model. That's why El Nino cannot be accurately predicted, it is a feature of the upwelling of cold water, resulting in a change in surface temperature.
Quoting Tate
I really see no reason why warming would cause ocean currents to slow down, because the earth would continue spinning. It could cause changes to them, perhaps even speed some up.
That's just one way to refer to that particular set of currents. It's also called the thermohaline circulation.
Quoting Metaphysician Undercover
The circulation requires a heat differential between surface and bottom water in the north Atlantic. As that area cools due to polar ice sheet melting, the differential is minimized. Scientists are presently keeping a close eye on it because the ocean currents are slowing.
Computers just enhance our ability to make predictions from what we know now.
Actually, I don't think the circulation requires a heat differential at all. As I explained, it is the product of the spinning planet. The heat differential is created by the uneven heating of the planet, by the sun, but this is not required for the circulation, which is caused by the spinning of the planet, not the heating of it.
And, it is really not accurate to say "ocean currents are slowing", because the currents are not at all stable, they are always in flux, constantly changing. While one current slows down a bit, another speeds up. So long as the earth is spinning, the water is flowing, and the moving water will transport heat when the surface is unevenly heated.
The thermohaline circulation does. It was in the link.
There are several articles out now that have called this assumption into question. For one: insolation is at a minimum now and there's no reglaciation starting. Another is that the geological record doesn't back up this assumption.
So what else could be causing reglaciation if not insolation minima?
A lot of articles are pointing to this:
"Understanding long-term history of North Atlantic intermediate to deep water circulation is important for assessing of the role of the thermohaline circulation (THC) in global climate change. Today, North Atlantic Deep Water (NADW) ventilates more than half of the volume of the deep oceans, affecting the physical and chemical properties of deep water globally. A growing body of geological and geochemical evidence demonstrates that at certain times in the past, the production of NADW, and with it the climate of the circum-Atlantic, changed at rates and with magnitudes that are of societal relevance. During the most recent glaciation, large reorganizations in the circulation of the North Atlantic Ocean and the Nordic Seas mirrored variations in air temperature over Greenland, suggesting that ocean circulation was tightly linked to North Atlantic climate over both glacial-interglacial and shorter timescales". Here
Models have previously left out consideration of slowing or shutdown of the thermohaline circuit. Since a number of scientists are now considering the possibility that this has been the real trigger for reglaciation since we entered the 100,000 year cycle, I imagine we'll be seeing those models soon.
If it did stop, it's possible that reglaciation could begin. We're at the right point in orbital forcing for another glacial period to take hold, which would soon drop the pCO2 in the atmosphere by cooling the oceans.
Just food for thought. If you want to discuss further, or get access to articles that are behind paywalls, let me know.
There have already been articles about climate scientists encountering resistance to a free exchange of ideas. Imagine that the thermohaline slows down even more than it has. Imagine scientists trying to explain that we're headed toward an event at least like the Little Ice Age, and possibly like the Younger Dryas, which would be devastating to the human population of the earth.
Instead of packing up and moving to Greenland, people would be returning to our original home: Africa, specifically, the Sahara.
The thermohaline circulation is not an ocean current, nor is it a group of currents. As I said already, it's a vague and extremely general abstraction, which is not at all useful for prediction purposes.
And, it is very common for THC to lead to faulty predictions.
Not to mention munchies and long drawn out philosophical discussions.
So, getting down to the brass tacks, a question: Is philosophy good/bad for the climate?
:snicker:
https://oceanservice.noaa.gov/education/tutorial_currents/05conveyor1.html#:~:text=These%20deep%2Docean%20currents%20are,very%20cold%2C%20forming%20sea%20ice.
Quoting Tate
You seem to be suggesting that the slowing of the circulation may trigger re-glaciation. but this looks to be backwards. Rather it is the melting sea ice that is reducing the salinity and thus the density of the water and so slowing the circulation. Re-glaciation would increase the salinity and thus strengthen the circulation.
But once reglaciation starts, it's self reinforcing, whether the thermohaline starts again or not. Ice sheets are considered by some scientists to be the most powerful force in the climate.
It hasn't started though; on the contrary deglaciation is accelerating and it is the loss of ice that we are seeing. It is bizarre to suggest that something caused by loss of ice will cause an increase in ice. I don't say it is impossible, but it at the least demands a very detailed explanation of the mechanism, and how it is powerful enough to overcome the positive feedbacks of ice loss already discussed above.
But of the links you have provided so far, there is not one I have seen that remotely suggests that a new ice age is at all likely in the next few thousand years. Rather they all seem to suggest that a new ice age has already been prevented by the rise in CO2 levels.
The shutdown of the thermohaline is caused by a loss of ice. It leads to an increase in ice. Scientists believe this has happened multiple times in the past. I think it makes more sense if you consider the wider context: that we're in a large scale ice age, stuck here by ocean currents that maintain deep water that never sees the light of day. Does that make sense?
Quoting unenlightened
Shutdown of the thermohaline is proposed as the cause of the Young Dryas. Do you want to look at whether anybody has tried to model that?
Quoting unenlightened
That's not true. There are a couple of articles that propose thermohaline shutdown as the trigger for reglaciation during the 100,000 year cycle. I posted one of them.
It's a remote suggestion.
Quoting unenlightened
That's just the one that says the Anthropocene started 6000 years ago. That's a cool one.
He's saying we've already passed one trigger point.
I haven't seen them, and I just looked back over the last couple of pages and still couldn't see any links I hadn't followed.
I'd really like to see where scientists are saying this:
Quoting Tate
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/younger-dryas
But that is a very different scenario, where the melting of land ice causes the growth of polar ice. Much harder to envisage the loss of polar sea ice causing an increase in polar ice.
It's slowing down now. here
I'm not sure what you're saying.
Did you want to explore the articles that say the slowing of the thermohaline might be the trigger for reglaciation?
I posted about why the previous explanation, which has been primary to long range modeling up till now, has been called into question. Did you see that post?
I know it (ocean circulation) is slowing down. I expect it to slow down because polar ice is melting and lowering the salt, and thus density of the polar waters, so they don't sink (see your own link that I quoted above). I do not see how a slowdown caused by the melting of polar ice can result in increasing polar ice. I am looking for links that support your claims, and not finding any.
A slow down or shutdown will be associated with a reduction in atmospheric CO2, resulting in cooling. But what's becoming apparent is that there isn't one magic bullet that initiates reglaciation. It happens when a number of factors are all in alignment: orbital forcing, precessional forcing (the Milankovitch cycle), and more broadly, just the fact that the climate is prone to glaciation for the last couple of million years.
Read this article, exploring the possibility that the THC (thermohaline circulation) is responsible for longer and shorter term changes in climate. It also talks about the debate about how the Younger Dryas actually started.
Here
And look at this one.
Thanks for engaging. I appreciate it.
Your first article makes this claim, but does not explain it. On the face of it, one would expect vigorous stirring to facilitate absorption of CO2 from the atmosphere. and lack of circulation to impede it. Any explanation?
The second link is not accessible to the Institute for Retired Busybodies, unfortunately.
Meanwhile, I have this:
http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html
All in all, the more I find out, the more the whole affair looks like humanity as a mad scientist in the process of blowing up his laboratory and speculating about whether he will be roasted or frozen or both.
Ex cathedra claims are being discounted in this thread.
When water absorbs CO2, it makes carbonic acid. A bottle of soda water has a high carbonic acid content until it's either warmed or shaken, both of which will make the water lose it's ability to dissolve CO2.
Quoting unenlightened
That's the one from Nature. I'll copy out the good bits. I've been wandering around the Potsdam website for a while. Fascinating stuff.
Quoting unenlightened
That's the reason I found the article about how we might have been tweaking the weather for the last 6000 years to be intriguing. It could be that something as fundamental to who we are as agriculture could be at odds with climate stability.
Yes so the effect of circulation is to cool surface water and allow increased absorption. So why the claim that it does the opposite?
Circulation brings warm water up from the tropics. When the circulation stalls, it ceases to be a heat conveyor. Is that what you mean? I'll look at it again. I may be missing something.
FYI, found a reference to the research about lower temperatures in the northern hemisphere: https://news.illinois.edu/view/6367/207427
Thanks for that. The effect on Europe I suspect would be what we have seen this year; drought. My secondary school education tells me that the mediterranean climate is "warm wet winters with westerly wariables, and hot dry summers". Without the warm water in the Atlantic, that would I guess change towards "cold dry winters and even hotter dryer summers". Fun!
But a much larger question would be the effect on Antarctica. Intuitively, there would be heating of the tropics and cooling at the poles, with much complexification, and thus a loss of temperate climate which is what tiggers and tea drinking monkeys like best.
I think the situation is a lot more complex than this. Evaporation also increases salinity, and this makes denser warm water, possibly increasing water temperatures at greater depths. Further, increased evaporation increases the flow of fresh water, and this makes greater surface circulation. But, as I explained earlier, surface flow is insufficient to replenish the volume of surface water flowing way from equatorial areas, so there will always be an upwelling of colder water in equatorial areas.
Quoting Tate
That's highly speculative. As I've explained, such currents change, but it's impossible that the THC, on a global scale, could stop. And these speculations you refer to are very unscientific. First, the article admits that the evidence is "proxy" evidence, and this is extremely susceptible to confirmation bias. Ocean currents, especially those at various levels of depth, have not been adequately measured. And, they admit that only nine out eleven of those "proxy" observations actually confirm this "slowing" thesis. Furthermore, the description of the THC in that article doesn't even include the freezing factor described by unenlightened. It seems to only described increased salination due to evapouration:
Quoting Tate
The problem with this sort of so-called "science" is that when dealing with long time scales without direct observations, it is impossible to distinguish cause from effect. So, we see a change in THC as coincident with a change in climate. Yes, of course, the two go hand in hand as two parts of the same phenomenon. But it is a mistake to conclude that one is the cause of the other.
Quoting unenlightened
The THC cannot shut itself off. The fundamental feature is that warmed surface water will move away from equatorial areas. This is 'forced' by the spinning of the planet and the consequent Coriolis effect. The replenishment of water, via surface mechanisms is not equally 'forced'. There is a force away from the equator at the surface, but not an equal push back toward it. This will always create an upwelling of colder water from the depths. The same process is observed on lakes with a prevailing wind, without any influence salination.
I think you may be right. I don't actually expect to model the climate in a paragraph.
Quoting Metaphysician Undercover
I think the situation is a lot more complex than this. And in fact links already given and quoted suggest that it can shut itself off, and has done, which does not imply that no movement at all occurs, vertical or horizontal. So some published support is required for your pontifications as much as for the rest of us.
I found this a helpful broad summary of many of the issues in this thread. Carl Sagan from 1985 when things were slightly less political.
The cause of global warming is the sun obviously, with the input into the atmosphere being part of the equation and the amount unable to exit as the result of it being trapped in gasses caused by fossil fuel burning another.
So, of course, if sun input changes, we could see another ice age, and equally of course, if we increase heat capturing gasses into the environment, we'll increase global temperatures.
He acknowledges humans have been impacting global temperatures for thousands of years. My assumption is that all plant life does to some extent as well.
Pay attention to his solution, which I find interesting as it acknowledges an almost impossibility of universal political agreement. That is, it's not clear that complete elimination of green house gasses from the West will do anything without the same by China and Russia. You can't dam half a river.
I don't know about highly speculative, since there's a consensus that it's slowing, but you're still making an important point: everything talked about in this thread is pretty speculative. There are a variety of reasons for that, but one of the big ones is that we still have unanswered questions, such as a solution to the 100,000 year problem.
That's how science rolls, though. Speculate, model, test, repeat.
Quoting Metaphysician Undercover
I'm going to push back on this. Climatology is science.
"The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled oceanatmosphere system. But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse warming. Analyses of past abrupt climate changes help to solve these problems. Data and models both suggest that abrupt climate change during the last glaciation originated through changes in the Atlantic thermohaline circulation in response to small changes in the hydrological cycle. Atmospheric and oceanic responses to these changes were then transmitted globally through a number of feedbacks. The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state.
"Most, but not all, coupled GCM projections of the twenty-first century climate show a reduction in the strength of the Atlantic overturning circulation with increasing concentrations of greenhouse gases13if the warming is strong enough and sustained long enough, a complete collapse cannot be excluded14,15. The successful simulation of past abrupt events that are found in the palaeoclimate record is the only test of model fidelity in estimating the possibility of large oceanatmosphere reorganizations when projecting future climate change.
"Paradoxically, although the THC in current models responds to freshwater forcings without delay, the largest deglacial meltwater event on record, referred to as meltwater pulse 1A (MWP-1A), occurs more than 1,000 years before the next significant change in the THC associated with the Younger Dryas cold interval39. This paradox may be resolved, however, if MWP-1A originated largely from the Antarctic Ice Sheet40, where its impact on the Atlantic THC would be substantially reduced.
"Some modelling experiments find that during the next few centuries, the THC moves to an off state in response to increasing greenhouse gases14,15,65. A reduction of the meridional heat transport into the circum-Atlantic region would partially compensate the warming due to increasing greenhouse gases, although such a change could have serious climatic consequences for the climate in the circum-Atlantic region through modifying long-established regional airsea temperature contrasts, seasonal variations in the direction and strength of wind patterns66 and the location of convective areas67. The implication of such changes on regional climate remains largely unexplored. Reorganizations in the THC would also change the distribution of water masses and hence the density in the world ocean. A warmer and more stratified North Atlantic would also take up less anthropogenic CO2 (ref. 68). On the other hand, other experiments suggest little or no reduction of the THC to the same greenhouse gas forcing13. This indicates the possible dominance of negative feedback mechanisms such as changes in the amplitude and frequency of ENSO69, or modifications of atmospheric variability patterns in the Northern Hemisphere70.
"The fate of the THC in the coming century largely depends on the response of airsea heat and freshwater fluxes to the increased load of greenhouse gases. Uncertainties in modelled responses are particularly large for the latter13. Moreover, the threshold for the occurrence of an abrupt change in a particular climate model depends on poorly constrained parameterizations of sub-grid-scale ocean mixing57. Because a complete THC shutdown is a threshold phenomenon, the assessment of the likelihood of such an event must involve ensemble model simulations71, as well as continued efforts to simulate past abrupt climate changes that so remarkably affected the global climate system.
The role of the thermohaline circulation in abrupt climate change
If you look at the Potsdam Institute for Climate Impact Research website, it looks like the articles discussing adaptation to climate change are quite a bit more prevalent than articles about stopping it. I think both avenues are important, though.
This is another interesting factor: brine rejection
But that's what I was saying earlier; that sea ice formation increases salinity and drives circulation and sea ice melting reduces salinity and slows circulation (other things being equal).
You can dam your contributory tributary to the river though which would have reduced the flow and shown that it could be done. The tragedy of democracy is that the next election is the event horizon of all democratic politicians. Oligarchs and dictators on behalf of the proletariat have no such excuse though.
Sad though to see how clear it was 37 odd years ago, and how very little has been done in that time.
Yes. I'll have to look into further.
What he says needs to be done can happen only through universal cooperation, which is the panacea that will cure far more imminent threats than global warming.
Given that we'll not get China to allow Taiwan self determination, much less get it to abandon thoughts of mining and using its own coal, perhaps we should reconsider our paltry efforts of trying to do the right thing. Having the moral higher-ground is of what value if our efforts don't ultimately matter?
It's a better place to be than the moral pit, for as long as there is any place to be at all. Nothing ultimately matters and we're all ultimately dead, so it's just a question of having a good looking corpse, because fuck it why not.
Ignorance is bliss.
The Chinese are building lots of nuclear power plants, which everyone should be doing. If Europe actually does wean itself off Russian oil and gas, that would help.
I agree that democracy isn't the organizational structure for this problem. Totalitarianism would work.
The solution remains more political than scientific. Most of Europe is aligned, but not so much the US, and surely not beyond the West.
https://www.yahoo.com/news/shelling-ukraine-nuclear-plant-raising-144759494.html
Quoting Hanover
Universal cooperation is a pipe dream. Also the idea that we can quickly de-carbonize is a fantasy it seems. The "political" part of the problem is the promulgation of impossible targets, but also, the unwillingness (due to the perceived unpopularity) to promote the idea that we (in the "developed" nations) should all use much less energy; drive much smaller cars, use public transport, do without air-conditioning unless absolutely necessary, stop traveling overseas, choose locally grown foods etc.
This Explains very clearly the problems involved with trying to de-carbonize rapidly.
Climatology is said to be a science, I do not deny that. And what you've presented here you seem to present as science, that's why I called it "so-called science". But the stuff you've presented and referenced, in this thread, if it is claimed to be science, is really pseudoscience. It's pseudoscience because the theories and predictions made cannot be verified or falsified
Quoting Tate
Yes, that's a fair representation of the scientific method, but what is lacking in your claimed scientific climatology is the "test" part. So all we have is 'speculate, model, repeat'. That's not science.
If it was published in Nature, it's science.
https://www.whoi.edu/news-insights/content/the-future-of-the-oceans-conveyor-belt/
https://www.whoi.edu/press-room/news-release/two-new-studies-advance-understanding-of-currents/
https://www.e-education.psu.edu/earth103/node/686
Notice, in the first reference, the changes to the THC currently observed are described as "natural variability". Beyond that, it's all speculation. And notice as well, the concluding paragraph of the third reference;
The THC (GCB) will not stop, the principles are simple. The earth's surface is heated unevenly by the sun. The earth spins therefore the Coriolis effect. Warm water will be moved from equator toward the poles, and cold water dropped to the depths, and moved by other forces toward the equator, to replenish surface water moved out from there by the Coriolis effect. The positioning of land masses has the greatest influence over how and where this occurs. Other factors also play a role.
Thanks for the references. You own summary above, though, is highly misleading. The principles are not at all simple in their interaction and you have entirely omitted the role of salinity. As I said before, no one is suggesting that all movement of water will stop under any scenario. However, radical changes in circulation can certainly happen due to climate change, that will in turn have a large influence on the climate. Models of complex systems are always simplifications, and always inexact. Like weather forecasts, climate forecasts are subject to error that increases with the timescale. But this does not make them unscientific.
I omitted the role of salinity because it is a secondary feature. The point is, that as secondary, changes in salinity cannot cause the GCB to actually shut off. Some articles place salinity as a primary feature, implying that cooled water would not sink if there was no salinity. But this is not true, as we notice in fresh water lakes.
The online articles about the THC, or GCB, are not very consistent with each other. Where they place the underwater flow varies greatly. Also, I've noticed discrepancy in the time required to complete the cycle, with reports varying between 700 and 1500 years. How can they talk about a slight slow down when there is that much discrepancy already? Also, it is stated in the quote I took, that in the practise of measurement, the flow sometimes does not even follow the path presumed by the model.
Quoting unenlightened
Radical changes will happen, there is no doubt in my mind. The big factors are the earth's spinning, its interaction with the sun, and the positioning of land masses. The land masses we know to be changing, with volcanoes and plate tectonics. These features seem to be attributable to internal forces of the earth. Changes to the properties of the water itself (salinity, turbidity, etc.) could also causes lesser changes which could appear to us as large changes, due to our limited observational time scale. Changes to the properties of the atmosphere, since winds are a driving force, would also change the THC.
I see that a number of scientists now speak about the water in the oceans in terms of water masses, like meteorologists speak of air masses. These are masses of water with similar properties, which may move in away similar to air masses. So we can make an analogy between a polar air mass, and a polar water mass. The air masses have boundaries and the boundaries are areas of turbulent weather. Differences in salinity exaggerate the boundaries. In the case of air masses, portions of the polar air mass move toward the equator, sliding underneath portions of the warmer air mass moving poleward. Along the boundaries we have the jet streams, where the mixing occurs. (I acknowledge this as an over simplification.) The jet streams are not stable, always changing, and sometimes even totally breaking down to reform in a new location. This lack of continuity makes them difficult to predict. Scientists have produced some success in predicting the jet streams in the short term, through extensive observation of the air masses. but the discontinuity presents a real problem. Movement can be modeled, but a lack of movement won't indicate where the next movement will be. This means that features related to the cause of movement are missing from the theories, requiring some "guess work" in the modeling, making the models unscientific in that sense.
If we take the jet streams as analogous with the water flow, we see that these are mainly east/west directional, and are the product of the mixing of air masses to the north and south. The jet streams do not take heat from the equator to the north pole, or cold in an opposite direction, the flow represents the mixing of the heat differential. Therefore I believe that the GCB, or THC, ought to be modeled more like this. Rather than as transmitting heat from equator to poles, it ought to be described as currents produced from the mixing of water masses with different properties. A water mass in contact with another, with different properties, will flow.
Quoting unenlightened
I disagree. The "guess work" which goes into these models is unscientific. That is the problem. True science is mixed with pseudoscience in a way where the outcome is models consisting of both. The true science does not have the required observational data, nor the required proven theories, to make the desired models. So the gaps are filled with pseudoscience. The simple issue is that the science required to make these models does not exist, yet the models are produced and presented as science. So they must be classified as pseudoscience due to the fact that the true science is contaminated within the model. Models contaminated with pseudoscience are not scientific. This is a problem which our computer driven society, which greatly facilitates model making, presents us with, unscientific models which people are inclined to call science.
And I disagree with you. Weather forecasting has become hugely more accurate since the advent of computer modelling, but it hasn't become more scientific, just better informed and capable of faster calculation. Science includes speculation and guesswork in every prediction - the more mature the science, the better the predictions, but perfection - never. The estimation of error is an important aspect of experimental science.
What are you saying here? We shouldn't have any opinions about anything scientific?
is a slippery slope. Many physicists and philosophers deny that psychology is a science by either physicists' or philosophers' standard, or for that matter by the standards of research psychologists themselves. But they're all wrong. Science is what science does.
We wouldn't be alive without the greenhouse effect. We just don't want to screw it up.
Weather forecasting has become more scientific. The computers use observational data in producing
their models. It is the increase in available observational data, and the computer's increased capacity to process observational data which has made weather forecasting more accurate. A prediction made with an absence of observational data is completely unscientific, relying on something other than science. And observational data is essential to science. So an increase in observational data in the forecast, which is what computer modeling gives us. means a more scientific forecast.
Quoting unenlightened
This I think is a feature lacking from common weather forecasts, which would improve the forecast, the estimation of error. Under some weather conditions, the forecast for tomorrow, or even the next day, is made with a high degree of certainty. Under other conditions the forecast is made with a lower degree of certainty. So the forecasters could include in the forecast a declaration of confidence. They could give the forecast for tomorrow for example, and qualify it with 'ninety per cent confidence', or maybe only 'seventy per cent confidence', or something like that. Then the further into the long range that the forecast extended, the lower the degree of confidence would be. It would be another tool in the forecaster's kit, giving interpretational guidance to the audience.
Quoting Changeling
That may be true, but as I've explained already, this thread is not concerned with a matter of science, it is concerned with a matter of speculation, and that is where a metaphysician is right at home.
Ah, of course. Well, there's a lot to do if we want to make the place like the surface of Venus. :wink:
Quoting Changeling
:up: I always like it when metaphysicians put things in the perspective of science because they could get outside of it and critique. Scientists must think within the context of scientific situation, otherwise, they lose their credibility. I only started appreciating science when I got into philosophy.