My own introduction to this topic was from the Encyclopedia Britannica. I was a small child and the encyclopedia was way out of date, so it said that there had been four ice ages. That's what they could see from looking at rocks.

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:

The climate swings back and forth between long glacial periods and short interglacials. — Tate

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.

It's just a picture of glacial cycling. There's no motive other than it's fascinating. This is going to be a long thread. Stick with me. :grin:

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. — Wikipedia

That's a fair summary. :up:

This thread should not be confused with global warming created by humans!

Fair warning.

That's a fair summary. :up: — 180 Proof

: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:

This. We can end this thread here and now.

This. We can end this thread here and now. — Benkei

:lol:

Likely so.

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.)

The Toba supereruption was a supervolcanic eruption that is believed to have occurred some time between 69,000 and 77,000 years ago at Lake Toba (Sumatra, Indonesia).

It is recognized as one of the Earth's largest known eruptions. The related catastrophe hypothesis holds that this event plunged the planet into a 6-to-10-year volcanic winter and possibly an additional 1,000-year cooling episode. This change in temperature is hypothesized to have resulted in the world's human population being reduced to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution.

@Agent Smith

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. — Wikipedia

Cool. So let's look at the science behind this. How could you object to that?

Quaternary glaciation

The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began 2.58 Ma (million years ago) and is ongoing. Although geologists describe the entire time period up to the present as an "ice age", in popular culture the term "ice age" is usually associated with just the most recent glacial period during the Pleistocene or the Pleistocene epoch in general. Since planet Earth still has ice sheets, geologists consider the Quaternary glaciation to be ongoing, with the Earth now experiencing an interglacial period.

So different people are using the term "ice age" in different ways.

@Tate

around 50,000 years — Wikipedia

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!

So different people are using the term "ice age" in different ways. — Michael

:up: I've been saying "large scale ice age" to try to specify.

That's a frigging long, long waiting time. — 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 we know is that we're moving into a trigger point now. — Tate

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

What is this "trigger point" you keep talking about? — Metaphysician Undercover

@Tate is pulling it out of his rear end. This is CC denial, hidden behind yet another mask.

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: — Metaphysician Undercover

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.

We don't take kindly to people inquirin' 'bout climate change 'round these places.

What do you think causes the shape of earth's orbit to abruptly change?

What do you think causes the shape of earth's orbit to abruptly change? — Metaphysician Undercover

It doesn't.

Can I suggest that we take this slowly, and provide sufficient detail to avoid misunderstandings as much as possible. I'm going to start with this https://en.wikipedia.org/wiki/Geologic_time_scale

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.)

it said that there had been four ice ages. That's what they could see from looking at rocks. — Tate

Do you mean looking at ice cores? Looking at rocks would involve much longer timescales.

The Last Glacial Period (LGP), also known colloquially as the last ice age or simply ice age,[1] occurred from the end of the Eemian to the end of the Younger Dryas, encompassing the period c. 115,000 – c. 11,700 years ago. The LGP is part of a larger sequence of glacial and interglacial periods known as the Quaternary glaciation which started around 2,588,000 years ago and is ongoing.

https://en.wikipedia.org/wiki/Last_Glacial_Period


Assuming you are talking about the cycles of the Quaternary glaciation, we need to consider This:

The 100,000-year-problem refers to the lack of an obvious explanation for the periodicity of ice ages at roughly 100,000 years for the past million years, but not before, when the dominant periodicity corresponded to 41,000 years. The unexplained transition between the two periodicity regimes is known as the Mid-Pleistocene Transition, dated to some 800,000 years ago.

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.

. 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 — Tate

Does this M.I.T. Technology review article jibe with what you are reading?

“…cyclic gravitational tugs from Jupiter and Saturn periodically elongate Earth’s orbit, and this effect combines from time to time with slow changes in the direction and degree of Earth’s 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 it’s 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)

We don't take kindly to people inquirin' 'bout climate change 'round these places. — Tzeentch

Enquiring is a-okay. Lying is not.

Can I suggest that we take this slowly, and provide sufficient detail to avoid misunderstandings as much as possible. I'm going to start with this — unenlightened

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.

Perhaps you can shed some light on that? — unenlightened

I'm familiar with the 100,000 year problem. We'll get to it.

Do you mean looking at ice cores? Looking at rocks would involve much longer timescales. — 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.

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 — 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!

Yes. He's saying the world is going to experience a climate whiplash which will likely make it difficult to maintain civilization.

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?

Have you read that whole article? — Tate

Yes, I did. It makes one appreciate that from
the planet’s 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.

the time scale of climate change will be barely noticeable compared with that of the next ice age. — Joshs

True.

What do you think causes the shape of earth's orbit to abruptly change? — Metaphysician Undercover

It doesn't. — Tate

"Abrupt" was your word.

This explains why reglaciation is always so abrupt. — 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.

They're caused by changes in the circularity of the Earth's orbit. — Tate

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.

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? — 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?