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Author Topic: Early Anthropocene  (Read 67082 times)

oren

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Re: Early Anthropocene
« Reply #100 on: October 29, 2018, 10:18:35 AM »
Honestly I don't mind, and we do spend too much time on our butt. But I'd expect at least the first sentence in an article on phys.org to be fact-checked.

Gray-Wolf

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Re: Early Anthropocene
« Reply #101 on: October 29, 2018, 12:28:49 PM »
I believe we find changes to the ankle bones of our prehistoric ancestors where constant 'squatting' altered to bones?

Folk on the move ( hunter gatherers ) would not be carrying chairs with them but would have sticks ( spears ) so squatting with the aid of that 'third leg' would have been their choice of rest positions ( better than permafrost soggy land surface!).

As we know from our folding 'camping chairs' a few sticks and a hide would fashion a comfy seat for in their semi permanent homes but out on the plains a stick and a squat would do just fine!
KOYAANISQATSI

ko.yaa.nis.katsi (from the Hopi language), n. 1. crazy life. 2. life in turmoil. 3. life disintegrating. 4. life out of balance. 5. a state of life that calls for another way of living.
 
VIRESCIT VULNERE VIRTUS

Archimid

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Re: Early Anthropocene
« Reply #102 on: October 29, 2018, 01:51:16 PM »
Vox_Mundi posted an image going from lower primates to the "sitting primate". Has anyone seen that image extended beyond the primates all the way back to the last mass extinction? In such image the earliest ancestor would look a lot more like this:

I am an energy reservoir seemingly intent on lowering entropy for self preservation.

AbruptSLR

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Re: Early Anthropocene
« Reply #103 on: November 04, 2018, 08:30:55 PM »
From the linked reference I focus on the possibility/probability that anthropogenic fires was a large source of the increase in atmospheric methane from 21 kya until the pre-industrial era (circa 1750):

Hopcroft, P, Valdes, P & Kaplan, J, 2018, ‘Bayesian analysis of the glacial-interglacial methane increase constrained by stable isotopes and Earth System modelling’. Geophysical Research Letters.

http://www.bristol.ac.uk/geography/people/paul-j-valdes/pub/148471653

Abstract: "The observed rise in atmospheric methane (CH4) from 375 ppbv during the Last Glacial Maximum (LGM: 21,000 years ago) to 680 ppbv during the late preindustrial era is not well understood. Atmospheric chemistry considerations implicate an increase in CH4 sources, but process‐based estimates fail to reproduce the required amplitude. CH4 stable isotopes provide complementary information that can help constrain the underlying causes of the increase. We combine Earth System model simulations of the late preindustrial and LGM CH4 cycles, including process‐based estimates of the isotopic discrimination of vegetation, in a box model of atmospheric CH4 and its isotopes. Using a Bayesian approach, we show how model‐based constraints and ice core observations may be combined in a consistent probabilistic framework. The resultant posterior distributions point to a strong reduction in wetland and other biogenic CH4 emissions during the LGM, with a modest increase in the geological source, or potentially natural or anthropogenic fires, accounting for the observed enrichment of δ13CH4."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Juan C. García

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Re: Early Anthropocene
« Reply #104 on: February 05, 2021, 08:51:02 PM »
Quote
Paul Crutzen, Nobel Laureate Who Fought Climate Change, Dies at 87
He named our age the “Anthropocene” and warned the world of threats that certain chemicals posed to the ozone layer.

Paul J. Crutzen, a Dutch scientist who earned a Nobel Prize for work that warned the world about the threat of chemicals to the planet’s ozone layer and who went on to push for action against global warming, died on Jan. 28 in Mainz, Germany. He was 87.
https://www.nytimes.com/2021/02/04/science/paul-crutzen-dead.html

A great loss.
Rest in peace.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

gerontocrat

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Re: Early Anthropocene
« Reply #105 on: May 21, 2023, 01:59:18 PM »
I am reading a book entitled "Islands of Abandonment" (which I will,talk about in book reviews") and came across references to William Ruddiman, who published a paper in 2003 claiming that as soon as humans started organised agriculture AGW started.

I found a later paper from 2007 where he revisits that paper and confronts challenges to its conclusions - it's at https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2006RG000207
There are only 175 citations - I guess mainstream climate science poohooed it.

Nevertheless, I find the logic of his hypothesis quite sound, and maybe deserves a revisitation given the amount of additional data collected and developments in climate science over the last 15-20 years.

Incidentally the greatest reforestation in the world today by far is largely involuntary - in the countries that were in the Soviet Union and Warsaw Pact - that started after the collapse of the Soviet Union and the resulting abandonment of much of the vast areas that were collective farms. In just little Estonia tree cover has increased by 500,000 hectares since the fall of the Soviet Union.

Below is a small part of the introduction to the paper.

The early anthropogenic hypothesis: Challenges and responses
Quote
Abstract
[1] Ruddiman (2003) proposed that late Holocene anthropogenic intervention caused CH4 and CO2 increases that kept climate from cooling and that preindustrial pandemics caused CO2 decreases and a small cooling. Every aspect of this early anthropogenic hypothesis has been challenged: the timescale, the issue of stage 11 as a better analog, the ability of human activities to account for the gas anomalies, and the impact of the pandemics. This review finds that the late Holocene gas trends are anomalous in all ice timescales; greenhouse gases decreased during the closest stage 11 insolation analog; disproportionate biomass burning and rice irrigation can explain the methane anomaly; and pandemics explain half of the CO2 decrease since 1000 years ago. Only ∼25% of the CO2 anomaly can, however, be explained by carbon from early deforestation. The remainder must have come from climate system feedbacks, including a Holocene ocean that remained anomalously warm because of anthropogenic intervention.

1. INTRODUCTION
[2] For decades most climate scientists have accepted four views of Holocene climatic change: (1) Rising greenhouse gas concentrations in the atmosphere during the 1800s mark the first major anthropogenic effects on global climate. (2) After the last remnants of the Laurentide ice sheet disappeared near 7000 years ago, orbital-scale temperature has remained nearly stable for natural reasons. (3) A small cooling gradually occurred at north polar latitudes in recent millennia, but it has fallen short of the threshold needed to initiate glaciations. (4) Small suborbital climate oscillations during recent millennia have been driven by variations in solar output and volcanic eruptions and by natural multicentury variability.

[3] These four views can be condensed into a single statement: We live in a naturally warm and stable interglacial climate. Recently, however, Ruddiman [2003] put forward a very different view of the Holocene in the “early anthropogenic hypothesis”: (1) Anthropogenic effects on greenhouse gases and global climate began thousands of years ago and slowly increased in amplitude until the start of the rapid increases of the industrial era. (2) Global climate would have cooled substantially during recent millennia, but anthropogenic greenhouse gas increases countered much of the natural cooling. (3) Had it not been for human interference in the operation of the climate system, ice caps and small sheets would have begun forming in north polar regions. (4) Shorter-term climatic oscillations during the last 2000 years resulted in part from pandemics that caused massive mortality, reforestation, and sequestration of carbon.

[4] This revised view can be summarized in this way: We live in a world in which peak interglacial warmth has persisted only because of the inadvertent impact of early farming.

[5] Several challenges to the early anthropogenic hypothesis have been published. The purpose
of this review is to examine these challenges, summarize the arguments for and against the original hypothesis, update its current status, and suggest future research that could further clarify key issues.

11. CONCLUSIONS
[233] Although slow in developing, the climatic effect of these early agricultural factors by late in the Holocene rivaled that of the subsequent industrial portion (Figure 22c). Because the climate system had time to come to full equilibrium with the slow greenhouse gas increase over thousands of years, the cumulative effect on global temperature during the time just before the industrial era had risen to ∼0.7°C (for a doubled-CO2 sensitivity of 2.5°C and anomalies of 35 ppm for CO2 and 230 ppb for CH4). By the early 2000s the global mean warming of the industrial era had also reached 0.7°C, but the rise in gas concentrations during the past century was so rapid that the climate system has not had time to reach the full equilibrium warming. In addition, part of the greenhouse warming effect has been canceled by cooling from anthropogenic aerosols. As a result the estimated preindustrial anthropogenic warming of ∼0.7°C effectively doubles the total net effect of humans on global temperature to ∼1.4°C.

[234] A final implication of the early anthropogenic hypothesis is that no natural (preanthropogenic) baseline existed at any time in the middle or late Holocene. The natural downward trends in CO2 and CH4 were overridden by human intervention thousands of years ago, and much of the natural cooling that would have occurred was thereby prevented. Anthropogenic factors also played a role in short-term CO2 and CH4 oscillations during the last millennium. A world largely free of human intervention did exist in the early Holocene, when the last of the northern ice sheets were melting and when insolation values were considerably different from those today, but the climate system has been continuously altered by human interference ever since.
« Last Edit: May 21, 2023, 02:06:40 PM by gerontocrat »
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El Cid

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Re: Early Anthropocene
« Reply #106 on: May 21, 2023, 05:26:27 PM »
There are also other theories that link the massacre of Native Americans (and subsequent reforestration) to the onset of the Little Ice Age:

"Nevle et al then got out their calculators and crunched the numbers. They estimate that for a population of some 40 to 80 million indigenous people, the total amount of deforested land would likely have amounted to something the size of California. And since most estimates suggest that close to 90 percent of the native peoples died or were killed after the Europeans arrived, that meant most of that land returned to forest. That many trees, they say, all of a sudden appearing, almost as if out of nowhere, could have resulted in a loss of some 2 to 17 billion tons of carbon dioxide from the air.

To further bolster their argument, they say that core samples taken from the ice in Antarctica have air bubbles in them that show a reduction of carbon dioxide by 6 to 10 parts per million between 1525 and the early 1600s."

https://phys.org/news/2011-10-team-european-ice-age-due.html

Similar things here:

https://www.nationalgeographic.com/environment/article/did-amazon-rainforest-contribute-to-little-ice-age-1600s

kassy

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Re: Early Anthropocene
« Reply #107 on: May 21, 2023, 05:31:35 PM »
I always liked his papers. In mainstream science they are not quoted that much but one of the topics that is discussed where it features is the uncanny stability of the climate in Europe when they built the megaliths. So very niche paleo stuff.

PS: El Cid thanks for that paper. I always thought it was logical (also see reforestation + human migration patterns after the Black Death in Europe for example they show a similar if more limited thing).
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