Discussion in 'Earth Science' started by sculptor, Aug 9, 2017.
That gap between this one and the next is the issue.
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That doesn't seem to be what was being discussed. What was being discussed was whether history would repeat itself, and - not to put too fine a point on it, but - that would include a gap between successive civilizations.
At some length of gap, it no longer gets the label of "successive".
This is especially the case when it immigrates, rather than arising in place.
The point being: civilizations have ruined themselves by ruining their environment - and not recovered, in any normal sense of being the same civilization, a successive civilization, or even the same or successive people. And the civilization currently risking that, the environment currently at risk - very high risk - is global.
The glaciers will probably return, eventually. But not for many thousands of years.
Wood to coal, no gap. Coal to oil, no gap. That pretty much covers the lifetimes of all living people. Any gap would be devastating in terms of modern lifestyles. Starting over if all science is lost could take millennia.
No they won't.
No they won't ... ever? I mean, nobody can predict the future, but best as anybody can tell, whatever humans do only delays the inevitable by a few millennia at most. The cycle of glaciation may well be triggered by rapid ice melt in the poles with shift the thermohaline conveyor by decreasing oceanic salinity. And that is of course, a bit too much speculation for my comfort. But the Earth has roughly a billion or so years before the Sun starts making it too toasty for life, so we're going to have some more glaciation cycles before it finally ends.
I suspect they will. Heck, humanity could wipe itself out in a few centuries, and within a million years or so we'll see another Milankovitch cycle start glaciation again.
OK, so very recent history. You don't count, say, the Dark Ages, where much of human technology was lost for centuries? Rome, Egypt, etc. You don't count anything BC?
They all depended on draft animals for labor and wood or charcoal for fire. If and when fossil fuels become impractical, we could be entering another dark age.
Presuming that we either don't engineer our way out, that fossil fuels will suddenly disappear faster than we can adapt (which is very doubtful).
That depends on the civilizations. Several civilizations have deforested and suffered the consequences, with the transition to coal or oil coming much later and in the form of a quite different civilization.
It seems most likely that we are still in an ice age, and the glaciers will return.
That being said: We may well be in a superinterglacial much like mis 11 or mis 39.
The thing is that we do not know why we are in an ice age, what brought us into this one, and what will bring us out, nor the signs that will signal the end of this ice age. We also do not know why the glacial cycles within this ice age come and go, nor why the glacial/inter-glacial cycles were about 41 k years in the beginning of this ice age and are about 100k years long now.
Pretending knowledge when one is ignorant is just silly.
But we are not completely ignorant. We have no complete and nailed down explication, but we do know some stuff and can exclude some hypotheses as well as identify significant factors. CO2 and methane and sulfides (both oceanic and volcanic), say. Orbital circumstances.
Ice ages are long term reductions in global temperatures, resulting in large polar ice sheets and glaciers.
So no, we're not in an ice age. We are currently seeing the exact opposite.
Most of the ice melting is a pretty good sign that the last ice age is over. We are now in a period of rapid warming, which is the opposite.
And the "argument from ignorance" is a classic logical fallacy.
In order to have an intelligent conversation, perhaps we first need to agree on the meanings of the terms in discussion?
"An ice age is a geologic period characterized by the presence of polar ice sheets and alpine glaciers(which we still have). Periods of major glaciation (commonly also referred to as ice ages) are scientifically termed glacial periods."
"By this definition, we are in an interglacial period—the Holocene—of the ice age. The ice age began 2.6 million years ago at the start of the Pleistocene epoch, because the Greenland, Arctic, and Antarctic ice sheets still exist."
(good so far? can we agree on the above?)
Ok that covers the northern hemisphere, but then we have Antarctica which seems to have been covered in ice by about 23 million years ago.
So, when did this "ice age" start?
65 million years of cooling, then 23 million years ago, then 2,6 million years ago----------to say nothing of the struggles of Cesare Emiliani.
We are living in the Holocene which is an interglacial period within this Quaternary ice age.
There is no evidence nor reason to believe that we are no longer in the Quaternary ice age.
Dr. Julie Brigham Grette introduced us to the existence of superinterglacials which may last 2-3 times as long a"normal" interglacial.
Which brings up the 400kyr problem. ( a beat frequency within the Milankovitch cycles?)
The last superinterglacial was roughly 400kyrs ago
So if the 400kyr theory holds true, then we may have the anthropocene within the holocene which may be a superinterglacial period
So, can we agree on the above?
If so, then the glaciers will return, the question of "When?" then becomes relevant.
Most of the ice melted during at-least 3 of the last 4 interglacials.
And, when the glaciers return will they be greater or lesser than the recent 4 glacial periods, and will they once again avoid the driftless area of north america?
I see lots of reasons to doubt that.
No, we are in the post-glacial age.
How do you know that?
Why is it that you think that we are in the post-glacial age?
Is it only you who thinks he/she knows this?
I read it in New Scientist. The amount of energy retained as a result of human industrial activity has disrupted the cycle permanently.
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