Interesting: "Towards the base, the ice is more than 120,000 years old and dates back to the last interglacial period, a time when the atmospheric temperature above Greenland was 5°C warmer than today."
It also shows how crazy it would be if we get the projected 2-3 degrees average temperature increase. Even in a period where we'd expect to be going into a new ice age; instead shooting to a previously unseen high temperature.
Yeah a warmer climate brings all kinds of horrible changes. But food still grows in the northern hemisphere. A colder climate is arguably even worse for us.
By the way, that’s no excuse to keep doing what we’re doing. Limiting warning at 2-3 degrees will be nice. Things get really horrific above 4. At some unknown point feedback cycles really kick in and we go to 5-10 degrees and get completely fucked. We really have to not find out where that threshold is.
The time scales for anthropogenic climate change and the previous temperature cycles are so different as to not be comparable.
I think you are overestimating the probability that humanity would be "long gone by then". Even if a series of catastrophic events + climate change make life as we know it (modern civilization, globalized society/trade) untenable, humans are smart and many places on earth are reasonably forgiving to survival. Not saying it would be comfortable tho.
I’m just saying that a silver lining of the mess we’ve made is that we probably won’t have that ice age in 50,000 years. We’ve likely disrupted the cycle.
The earth varies in distance to the sun and axial tilt and precession. Like waves, there factors can either overlap and somewhat cancel or they can stack for a larger effect.
It’s unclear that it would play out that way. One could look at what happened the last time it stopped to get some idea, but things are different this time. We have a lot more atmospheric CO2.
IPCC predicts some local tipping points at 4C but global tipping points are much higher.
* 170,000 years ago: humans are wearing clothing by this date.
* 125,000 years ago: the peak of the Eemian interglacial period.
* ~120,000 years ago: possibly the earliest evidence of use of symbols etched onto bone
* 75,000 years ago: Toba Volcano supereruption that may have contributed to human populations being lowered to about 15,000 people
The Eemian climate is believed to have been warmer than the current Holocene. Changes in the Earth's orbital parameters from today (greater obliquity and eccentricity, and perihelion), known as Milankovitch cycles, probably led to greater seasonal temperature variations in the Northern Hemisphere. During the northern summer, temperatures in the Arctic region were about 2-4 °C higher than in 2011.
The hippopotamus was distributed as far north as the rivers Rhine and Thames. . . . The prairie-forest boundary in the Great Plains of the United States lay further west near Lubbock, Texas, whereas the current boundary is near Dallas. . . . Sea level at peak was probably 6 to 9 metres (20 to 30 feet) higher than today . . . .
https://en.wikipedia.org/wiki/Cerutti_Mastodon_site#Criticis...
This article is much more sympathetic (and also a fun read):
https://www.latimes.com/local/california/la-me-cerutti-masto...
I’m no expert but it seems like this is still a controversial idea.
The usual shallow, reflexive objection is that the bones must have been broken and carefully re-arranged via being run over by construction equipment. This absurd suggestion has been very thoroughly demolished without assistance from construction equipment. It is hard for dump truck tires to produce green-stick fractures in 130,000-year-old bone, or to put bone fragments into the pores of stones and then move them yards away, all while underground.
Given that we're so close to being able to do it, we honestly need a Manhattan project initiative to push it through to reality (with the outcome being the machine and process to do the drilling).
Which is to say: You Will Be Having Bigger Problems.
Recovery from regional meterological catastrophes is well within human capabilities.
How can people not generally understand the connection?
I'm honestly a bit shocked.
And what's with the weird tone? It's a super banal point that our food requires sun. I highly doubt you're "shocked" by it.
Though as a corollary, such an event would be civilisation-ending in any regard.
It's also ... highly rare. Somewhere in the 1 in a million to 100 million year range, which is to say, not only longer than the planning horizon of most human institutions, but well outside the existence of the human species for the most part.
It's also well beyond the available supply of terrestrially-minable uranium,[1] and possibly of ocean-extracted uranium,[2] and thorium[3]. Breeders might be another option, though I've seen no substantive estimates of total fuel availability for that case either.[4]
But as an argument favouring nuclear over other energy options ... this is pretty silly, really.
About the only viable defence against such a risk would be, and I say this as someone who's markedly pessimistic on space colonisation, independent and self-sufficient habitations off-Earth: YACP.[5]
________________________________
Notes:
1. If we relied on naturally-occurring terrestrially-mined uranium for all present human energy consumption ... supplies would last fewer than two decades. This is seldom mentioned by nuclear advocates.
2. This offers a potentially much larger supply, as uranium is present as a solute in seawater, but viable industrial-scale extraction is unproven and would require filtering vast quantities of seawater.
3. Thorium is reasonably abundant, though I'm not quite sure how abundant. Thorium-based reactors are not much used, and the concept of molten-salt reactors (MSR) which gained some popularity in the past decade ... faces some very significant engineering hurdles. Managing high-temperature highly-corrosive radioactive salts is ... challenging.
4. Breeders produce plutonium. And now you have two, or more, problems.
5. Yet Another Challenging Proposition.
The key question is: How much CO2 did that super-eruption emit into the atmosphere?
In our hurry to attribute climate change to our meager impact on this planet, we tend to forget what horrors an eruption of this magnitude can cause. And who knows how many of them happened during the past millennia.
I've never found a CO2 estimate, but did find that it's a significant amount of that mass, as is SO2.
It wasn't worth me doing more of a sketch since it's not clear how to model the effects of such a massive system.
I was struck tho, that the magnitude of this and a few other events in the not too distant past, are vastly larger than even all put nuclear war
It's not clear to me that our CO2 emissions are very significant in comparison
<https://en.wikipedia.org/wiki/List_of_largest_volcanic_erupt...>
As for the gaseous component of ejecta:
Water vapour is consistently the most abundant volcanic gas, normally comprising more than 60% of total emissions. Carbon dioxide typically accounts for 10 to 40% of emissions.
<https://en.wikipedia.org/wiki/Volcanic_gas>
Citing: H. Sigurdsson et al. (2000) Encyclopedia of Volcanoes, San Diego, Academic Press.
(Late edit: though I note that this seems to discuss percentages of gaseous emissions, not total ejecta. Anyone have a better source here?)
One of the largest volcanic events I'm aware of is the Siberian Traps eruption, about 250 mya, with a volume of about 4 million km^3, another three orders of magnitude greater than Tomba.
This has been linked to the Permian–Triassic mass extinction event, with the mechanism being release of methane clathrates and/or stimulating growth of a microbe which released vast quantities of methane into the atmosphere, killing ~81% of all extant marine species and 70% of terrestrial vertebrate species.
<https://en.wikipedia.org/wiki/Siberian_Traps>
"The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system during this period."
-- Wikipedia, citing Wu, Yuyang; Chu, Daoliang; Tong, Jinnan; Song, Haijun; Dal Corso, Jacopo; Wignall, Paul B.; Song, Huyue; Du, Yong; Cui, Ying (9 April 2021). "Six-fold increase of atmospheric pCO2 during the Permian–Triassic mass extinction". Nature Communications. 12 (1): 2137. Bibcode:2021NatCo..12.2137W. doi:10.1038/s41467-021-22298-7.
<https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extin...>
Yeah, it's the comparison between DRE and Gas ejecta that got me bogged down before.
Having now given up, I asked ChatG4. It says "the mass ratio between DRE and gaseous emissions might be on the order of 20:1 to 100:1", no citations ofc.
So, just as a strawman and using your 10-40%, on the low end .01.1 = 0.001, high end .05.4 = 0.02. So .1%-2% of ejecta by mass is CO2 emissions. Hah :)
Using my orig figure for Toba of a billion gigatons of ejecta, of which roughly a million gigatons would be CO2. Correct math?
Human GHG emissions are ~50 Gt/year.
Mt St Helens, for example. Not the largest eruption.
But a landslide of approximately 2.5km^3 (over 3 billion cubic yards).
Okay, some say, so that is a lot of earth...
and then you learn that the landslide was moving at speeds of up to 160mph.
That's a LOT of energy.
Geologists. And the answer is "none" for the past 25 or so millenia, and "one" since Toba.
Also, unless you've had supervolcanoes go off in your bedroom and didn't tell anybody, the evidence for human impact is exceedingly clear.
Geologists might know, same as astronomers might know what Black Holes and Pulsars really are.
On the other hand, it is a geologist's call to search for answers and for truth. Saying that they truly know is the same as saying nothing.
We at least have a significantly large list of what we know [1] - that's part of the purpose of core drilling, the ash deposits worldwide can be linked together to estimate where ash traveled to. Also, craters and their surrounding can be drilled into to determine eruption events.
[1] https://en.wikipedia.org/wiki/List_of_large_volcanic_eruptio...
The size and frequency of the largest explosive eruptions on Earth, Mason 2004
https://www.researchgate.net/publication/227000709_The_size_...
Of course the people will feel the local rise of temperature in asphalt-ridden and industry-polluted streets. It's logical.
This does not mean that global climate has changed.
Bottom line: we need large scale carbon capture quickly because even if we reach net zero CO2 will take millenia to drop back to the level it was pre-industrial revolution.
Edit: I wouldn't focus on "pre-industrial levels" specifically, the point is that there is too much now so we most likely want concentration to drop as soon as possible.
The CO2 curve 800000 years back is an excellent example.
CO2 in air bubbles in ice will diffuse into the ice during the many millenia the ice have been stored under pressure. You can therefore expect the ice core CO2 to be lower than hypothetical atmospheric measurements at the same time.
The diffusion is expected to progress fastest at the start, and then more slowly.
Still the artifact is absolutely obvious as the CO2 concentration peaks are lower and lower the further back in time it goes.
Yet of course someone had to splice it all together and not even add error bars.
[0]: https://www.antarcticglaciers.org/glaciers-and-climate/ice-c...
https://www.cambridge.org/core/journals/journal-of-glaciolog...
They have found some meltwater layers with unexpectedly large quantities of CO2 > 750ppm.
But they also show that there is unexpected heavy diffusion around the meltwater layers. And they argue very compellingly, that the ice core CO2 records have been smoothed through natural diffusion.
Why is this information not given when showing this graph?
What's the causal explanation behind that much CO2 though? Super-volcano eruptions?
But from the layers around it, it becomes clear that through the years these high CO2 bubbles leak CO2 to nearby layers.
And so CO2 highs are diminished in the ice core record and CO2 lows have been raised.
It is well-understood that many ice cores give the same relative shape of peaks of various gasses through time.
Going from there to claiming knowing the absolue concentrations without very large error bars, is just not science.
"Carbon dioxide measurements from older ice in Greenland is less reliable, as meltwater layers have elevated carbon dioxide (CO2 is highly soluble in water)."
The short term solution/bandaid is pumping SO2 into the stratosphere while we figure out carbon capture.
Because it would be expensive, but it would kill several birds with one stone: we (1) prove whether the concept would work on Mars, (2) develop the technology to do it, and (3) unlike SO2 in the atmosphere, "switching it off" or modifying the scale of the effect can be done almost instantly (you could remove the swarm by having it fall back to an Earth orbit).
As a layperson, it's just one more reason I so wish we'd invest in nuclear. Nuclear powered DAC plants might be the only way to scale it fast enough. Sure, it would still be expensive, but that's much cheaper than not massively reducing CO2 in the atmosphere.
Which is why keeping temperature down with SO2 during that time makes sense.
The mechanism is well known from volcanic eruptions, and it only lasts (from memory) 1-2 years in the stratosphere, so if something goes wrong, it can easily be tapered off.
We also have a great deal of methane leakage, which is usually cited as 25-100x, and we may soon have a lot of hydrogen leakage, at >100x. Rocket launches are installing water vapor, another one, into the stratosphere like never before.
So even if we got CO2 down to a pre-industrial level, we would still have heat forcing from the fluorine- and other compounds.
Capturing CO2 is kind of pointless until we get emissions under control. I.e., a dollar spent preventing emissions buys much more than a dollar spent capturing. Solar panels and wind turbines directly displace mass emitters of CO2.
On the other hand, as said, CO2 stays for centuries if not 1,000+ years so at this point net zero is only half the job though probably the hardest part.
"The planet did exist/will exist just fine without us" is a pretty worn truism. You might as well wryly note that water isn't natural because everything was hydrogen once.
Empirically observed, atmospheric CO2 went from ~320ppm to ~410ppm from 1970 to 2020[0], during which period the human population more than doubled from ~3.7B to ~7.8B and yet deaths caused by climate dropped threefold[1] (not 1/3 the rate; 1/3 in absolute number).
[0]: https://www.climate.gov/news-features/understanding-climate/...
Polonium by that ultra-short-relative-term reckoning is not only harmless as it you still feel fine 10 minutes later, but actually healthsome as you rather feel refreshed by the delicious green tea you just drank in that 5-star hotel bar.
1. https://energyeducation.ca/wiki/images/8/8f/Ice_ages2.gif
We want to return to pre-industrial levels because we’re used to it and we liked it more then.
Scrappy because, well the planet doesn't quite become uninhabitable and we're starting from the end-game. Science fiction also had me expecting some very cool terraforming infrastructure, not psy-ops to get the serfs to eat bugs.
A colossal volcanic eruption could do the trick, and those seem to happen rather unnervingly frequently.
And I agree: the history of the Earth is interesting. Which is why so many people study and work in the field of geology.
I'm completely an armchair ponderer.
It does make one wonder if any ancient sea fearing humans happened to carve a world map into a durable material such as granite which could have survived until the modern historic era. Maybe such a map, or other mythological artifact fueld the Roman idea of Terra Australis Incognita
/End rampant unsupported armchair speculation
With no evidence I believe navigation cues were built into the vessel. By keeping celestial bodies aligned with marks on the vessel one can achieve a seasonal calendar as well as documentation on how to modify the configuration for the next leg of the journey.
Source: Have a Pacific art collection, have been to most of the major museums on the subject, interested in sailing, authored some of the Wikipedia (featured) articles on related watercraft.
What I think is interesting is the physical representation of an oral tradition. This is different than writing as employed today.
What I seem to be noticing is that the ancients used calculus all the time but it was the geometric tools that they used.
This gave technology a form.
Arabic numerals made tabular data more useful leading to the more number based tools.
This seems to have removed the form from technology.
The American south (Arizona, Florida) were tiny and unimportant until air conditioning entered the chat. Phoenix was at 100 thousand people in the fifties.
The cold makes us think, the cold make us survive, keeps us on the edge - where we need to be. Respek the cold!
Sumeria and Egypt both had seasonal flooding. Italy and Greece have winters that are cold enough to disrupt agriculture. The Aztecs and Mayans had seasonal floods. The ancient Chinese empires had both. Japan has winters. The list goes on.
The Inuits of Greenland and Sami people of Lapland didn’t have Aristotle or Confucius.
I find it hard to believe they wouldn't philosophise at all. Confucius got famous (like sun tzu et al) because his ideas were written down, published and spread.
- What caused the temperature above Greenland to be 5°C warmer than today? Why is it cooler now compared to 120,000 years ago? What causes the interglacial periods? Is glaciation the more common state of the climate?
- The article says the ice sheet is melting at the bottom? Why? Pressure from above? Friction from movement? Heat from the Earth? Something else?
- Was the ice sheet shrinking or growing when the temperatures above Greenland were 5°C warmer than now? Does existence of the ice sheet imply that 5°C warmer for some period of time is not enough to melt the Greenland ice sheet?
- How much climate data has been lost to melting from the bottom? Is the ice sheet thickening or thinning compared 120,000 years ago? How would we know?
- How much has the Greenland land mass moved in 120,000 years due to plate tectonics? Could this have impacted the ice sheet in this short amount of time?
- Humans adapt. How did humans adapt to a climate that was warmer by up to 5°C 120,000 years ago?
- How long did the warm temperatures persist 120,000 years ago? 10,000 years? 50,000 years? Or more?
- Could a cooling climate be more worrisome to humanity than a warming one?