Why and when the Sahara Desert was green: new research
phys.org
phys.org
Edit: found the mention, he's talking to folks from the dogon tribe in mali, [0]@29min - 30min says that the area was heavily forested 500 years ago. The location is the bandiagara escarpment, old cliff dwellings [1]. All the episode of Sahara are on youtube, I highly recommend the series.
And we are killing it by diverting water from it.
When the problem is caused by all humans in the world, then no one feels pressured to do anything.
If you could instead name people individually, they would have to take a stand to actually do something about the issue.
My point is that this is what it's usually meant by "we are not doing anything about it". It generally means that there is not enough collective awareness about an issue for the people involved to have enough incentives to do the right thing.
Some people observe that the issue is under somebody else's direct responsibility but draw the conclusion that the responsibility chain ends there.
Other people instead think it's their responsibility to apply some sort of pressure from outside and failure to even attempt to do so extends the responsibility of the inaction to them too.
Some of those people extend their feeling of responsibility to also shame people for not shaming other people.
This is all natural and human and as with all human things it functions well until it fails catastrophically
When "scientific" articles write that a model "confirms" some conclusion, they are just wrong. Given enough free variables, you can construct a model that does anything you want. Models confirm nothing.
"The results confirm the North African Humid Periods occurred every 21,000 years"
No, they don't. Did the Sahara green every 21000 years? except when there were ice sheets? Only physical tests can confirm that. Do these greening phases correspond with orbital precession? Statistics can confirm that correlation. Running a model can test hypotheses of causality, but it doesn't "confirm" anything, least of all physical facts.
Or models showing some solution to the Fermi Paradox, and proponents claiming that the mystery is finally solved. How do they know the model is accurate?
Nothing is ever solved or proven. Theories get stronger and stronger evidence. Believing in a theory doesn't in any way help you make sense of the world. We just do it for expediency of communication.
There may be a theory that enjoys better predictive success for a while, but if everyone always believed in a singular “chosen” theory then we’d get nowhere: to evolve a better theory, you have to come up with and believe in something other than the preexisting one. Thus, it is normal for multiple theories to coexist at any given time.
Crucially, a theory is all map no territory, always and necessarily. It describes something we do not understand in terms of something that we do understand. At its core, it is a metaphor—and more than one metaphor can be useful, each in a slightly different context.
What I find tragic is that STEM-inclined crowd might have sort of triggered that defensive reaction by supplanting religion directly with natural sciences. Sometimes when you point out something similar to this thread (that physics does not make statements of absolute truth, there are only models of which none can be fully provably correct and complete, etc.) you encounter vicious insistence that the world is literally the way it is described in physics textbooks or Wikipedia—and it will stay that way until we are blessed with a new explanation for how things really are. You can notice how to a religious person this might feel indistinguishable to a competing religion, rather than an orthogonal aspect of worldview (it is completely possible to be both religious and a natural scientist).
Come to think about it, even your comment sounds slightly off to me in this way, primarily due to the mention of “explanatory limits”. I would prefer another term (possibly “predictive limits”). Again, “explanatory limits” makes it sound as if GR or QM (or X or Y) is capable of “explaining” something. Taking a model, just one metaphor that fits how some aspect of apparent reality behaves in response to input or another observation, and using that metaphor to explain how things are in some objective sense (which is what I take “explanatory” means) is, to me, a misuse of the model. The fact that the model works for some of our purposes makes it useful, but does not grant it explanatory powers.
I wish more of us techies resisted the urge to see in natural sciences explanatory powers that they do not possess, and instead branched a bit into philosophy—which can actually provide some grounds for meaningful discussions on topics that are out of scope of natural sciences per se. (As a side-effect, this might also make us more understanding and bearable to talk to for someone on a different bandwagon than ourselves.)
Beyond this I'd also add that many 'rock solid' theories do contradict each other. The obvious example being relativity and quantum mechanics which have mutually exclusive things to say on countless topics ranging from black holes to the nature of time itself. Both work phenomenally well and have abundant evidence in their own bubbles, but side by side - they can't both be true in their current state.
Better not use a bad map, but there can be more than one good map depending on what you need it for.
Here's mine: there is a "correct" set of theories (or truths) that the universe adheres to, we're just nowhere close to even guessing at them yet. But current theories can be closer or farther to them
But I've long had the pet theory that the Green Sahara is the origin of the Eden Myth.
Homo Sapiens origin, lush vegetation, turns to dessert for some reason beyond our comprehension...
Before agriculture, people lived as hunters and (mainly) gatherers. The life of a Hunter-gatherer is, surprisingly, mostly leisure, because of the abundance of food and the low population density. Even Kalahari Bushmen, who had been forced to live in the dessert, were found to average only about 1 1/2 to 2 1/2 hours of productive labor a day in a study [1].
In the bible, God's punishment is [2]:
“Cursed is the ground because of you;
through painful toil you will eat food from it
all the days of your life.
It will produce thorns and thistles for you,
and you will eat the plants of the field.
By the sweat of your brow
you will eat your food
until you return to the ground,
since from it you were taken;
for dust you are
and to dust you will return.”
[1] Stone Age Economics by Marshall Sahlins (https://archive.org/details/StoneAgeEconomics_201611)
[2] https://www.biblegateway.com/passage/?search=genesis%203&ver...
After eating the fruit God lists a number of consequences, which sounds somewhat like a punishment, but that could just as easily be interpreted as "well, I didn't want this to happen to you, but now that you got to this point, you'll have to deal with the following". That includes increased pain in giving birth (a consequence of having larger brains), and the rise of agriculture. Eve is also only named after eating the fruit, not before.
The snake gets cursed for what it did, and so does the ground, but not Man. God even goes so far to provide them with clothes, and acknowledges their growth.
The tree of knowledge of good and evil is basically just the spark of consciousness. Humans are unique in our ability to consciously foresee and plan for the future.
On the one hand, that's a blessing because we've made tons of progress towards alleviating objective suffering and scarcity.
On the other hand, it's a curse, because we always have to be aware of the impending inevitability of our death. We can't ever completely live in peace and paradise ever again, because we have become conscious of our existence and the context our life experience exists within.
Would it be better to not have gained that spark of consciousness and live the paradise of ignorance as animals in the wildreness? Lives at peace except for occasional bursts of pain and terror.
It's amazing that the majority of the world's population is descended from the couple of hundred individuals that left during one of these greening periods.
[1] https://www.bbc.co.uk/iplayer/episode/b00kfqps/the-incredibl...
Apparently Libya has a huge ancient aquifer (or several aquifers really) that they built pipelines to access, and now that's their main source of fresh water.
The aquifers, being left over from a previous era when Libya got a lot of rain, are not being refilled by anything.
Is this the case, and if so, does that mean the Amazon is only as old as the desert version of the Sahara?
Edit: bit of an answer here for anyone curious: https://earthscience.stackexchange.com/questions/2566/what-w...
https://justdiggit.org/what-we-do/landscape-restoration/wate...
(That site breaks the url bar though; I had to get that via a search engine. Wtf.)
https://www.earthdate.org/episodes/darwins-terraforming-expe...
When settlers showed up, it was essentially river running through a desert landscape. They dug canals to support agriculture and the landscape greened up substantially.
A lot of water law and patented water development tech happened in Fresno County. It's essentially a modern "hanging gardens of Babylon" situation and no one seems to talk about it.
In the Sahara and the Middle East, which are sunny and warm, if you add water plants grow fast.
We can imagine future scenarios in which fusion or solar are used to power large-scale desalination and irrigation to represent deserts from the coasts.
So… as we finally exit the current ice age we should expect a green Sahara?
If by "Ice Age" you mean period of glaciation - the most recent one ended ~ 11,500 years ago after starting some 120,000 years ago.
We're not currently in an "Ice Age" .. although by general expectation of this cycle we should be slowly moving into one . . . save for this recent rapid rise in C02 and atmospheric insulation increase caused by the most recent century of accelerated human activity.
See the enlarged graphic from the Nature article this thread is about:
https://www.nature.com/articles/s41467-023-41219-4/figures/1
or the full original paper:
https://www.nature.com/articles/s41467-023-41219-4
> ... we should expect a green Sahara?
Well, as noted we've rather changed the system parameters a fair bit, it's difficult to know what to expect where anymore other than a general increase in the amount of trapped energy at the lowest sea | land layers globally.
It's enough energy to eventually tip the otherwise periodically stable climate cells into all manner of not seen before new redistributions of climate activity.
The GP to whom I replied referred to the ~ 21 Kyear glaciation cycles associated with humidity changes in the Sahara, I specifically asked about what they meant by "ice age" and pointed out that now other parameters have been altered (the insulative properties of the atmosphere) we can't reliably predict how specific regions will change in the future on the basis of the past.
Your own link clearly differentiaties between geological "Ice Age" (Quaternary glaciation of the past 2.5 million years) and the popular notion of "Ice Age" (glacial cycles during that time).
Hence why I carefully wrote:
> If by "Ice Age" you mean ..
Do by all means contribute to the discussion, that is so much better than just playing the game of "gotcha's" (or whatever it is you're doing in your comment above).
https://en.m.wikipedia.org/wiki/Ice_age
Basic definition is when ice covers both poles
This specific research tightens up the timing and driving factors for the specific Sahara region (Libya, Egypt, Sudan) and doesn't relate to the Arabian Peninsula which is an almost seperate landmass more than three quarters surrounded by sea water.
On that landmass the Arabia Felix region (modern Yeman (mostly)) is known to have been greener in the past.
That would fly in the face of conventional thinking which is that Canada will be temperate and the Sahara will be more arid.
If you go up the hills to the plains of San Augustin where the VLA radio telescope that is around 7000 feet in elevation and I think a bit cooler and wetter and that is a very pretty grassland where you see big herds of antelope grazing and you might think you were in Africa.
It's pretty clear that bad things happen, even when white people aren't around.
With that said, Spanish and American colonization of the Southwest has radically changed the landscape. Much of what's now low brush used to be substantially more vegetated, similar to organ pipe national monument. Mesquite was rare outside intentional cultivation. It's actually an invasive species from the separate Chihuahuan deserts in Texas that was spread alongside cattle. Another fun fact is that prior to colonization, no part of AZ+NM was more than a day's walk from water (~20mi), which was important to long distance travel and later the Apache wars. That's no longer true due to groundwater depletion.
There is some stuff along route 66 that suggests the desert was there longer than humans though. One example is the crater they used for moon landing training. It’s basically undisturbed, and is extremely old.
I imagine many millions of large mammals and birds and insects also died.
Apparently Frankenstein and Dracula were both born that 'summer' at one of Byron's gatherings. Something to pass the time indoors.
That’s very far fetched.
> which is believed
By whom? The little ice age peaked in the 1600s.
> The eruption may have helped trigger the Little Ice Age, a centuries-long cold period during the last thousand years.
https://en.wikipedia.org/wiki/Little_Ice_Age
> In a 2012 paper, Miller et al. link the Little Ice Age to an "unusual 50-year-long episode with four large sulfur-rich explosive eruptions, each with global sulfate loading >60 Tg" and notes that "large changes in solar irradiance are not required."[8]
https://globalnews.ca/news/4924534/little-ice-age-death-55-m...
> The elimination of nearly 55 million, or 90 per cent, of Indigenous people in the Americas during European colonization led to global climate change and the “Little Ice Age” of the 17th century, a recent study finds.
In fairness, the Samalas Eruption did not directly lead to Ghengis Khan or Black Death. But during the Little Ice Age - the populations reduced by ~90%.
Specifically in the Americas, not the whole world. Also I don’t see how climate change was the cause.
European population had already recovered to its pre black death peak by the 1400s and had significantly surpassed it by 1500 (78 vs 90 million).
Your argument is similar to “Everyone would have died anyway; this thermonuclear winter just sped it up. Totally not humanity’s fault we live in a bunker.”