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Lazaridis 2024 - Associated Climate Data
#1
I wanted to post some climate data for the area and time-frame highlighted in the Lazaridis paper, basically based on this map:

   

First up are some measurements taken from peat samples, near the southern extent of area 1. These charts show a very significant increase in temperature and a decrease in precipitation between 5500-5000 ybp. The coldest months notably go above freezing, while the warmest months spike to 2x the long-term average, since then. Precipitation drops by 40-50%. Unfortunately, measurements only cover back to 5500 ybp, or 3550 BCE, while the Lazaridis paper indicates migration from this region ca. 4400-4000 BCE (6350-5950 ybp).

   

However, I also made some plots from climate models/simulations, which fortuitously focus on 6000 ybp, the period when migration from 1 is indicated. These show 100-year average temperatures for summer and winter months. These show winter temperatures in area 1 generally at or above freezing south, decreasing north. Summer temperatures are warm, in the 23-25 range. Combined with the peat samples above, this indicates that there was a sharp dip in temperatures between 6000 ybp and 5500 ybp, before temperatures spiked again.

   

Next up is a look at sediment samples from Lake Van, near area 4 from the study. These temperatures and precipitation plots are a little more stable. While there are oscillations, the magnitude is generally smaller. Potentially worth noting is that precipitation increased roughly 33% prior to indicated migration into the region, and while it oscillated from there, the long term average remained generally elevated for the next 1000 years, dropping again around the time of migration from area 3. 

   

Finally, I have included precipitation and temperature plots from peat samples near area 3. To me, the only really notable change is prior to migration from 1 to 3 (shown in black dotted line), specifically regarding coldest-month temperatures. The indicated date of migration immediately follows recovery from a cold period, during which winters dropped below freezing, returning to above-freezing temperatures year-round. There is a similar reduction and recovery in GDD5 (growing degree-days). I don't notice any massive changes on the later date (grey dotted line) which corresponds to migration from area 3 and expansion across the Steppe.

   

I'm still working on conclusions. It is hard to identify a climate-driven motivation for migrations from area 1, given discontinuity in data, aside from a hint of some temperature changes. However, one general pattern that emerges is expansion into areas recovering from changes. In other words, it doesn't seem to have been necessarily local climate changes driving people from an area. Rather, it may have been that nearby areas were put under stress and became relatively depopulated, opening up room for expansion and drawing people to new areas. I think particularly if these areas were inhabited by farmers, and precipitation or temperatures drastically changed, this would have put stress on that kind of economy. This would have been particularly true if plague also accompanied it. None of this is groundbreaking work, but I think that's what I'm seeing here, and seeing this made me think about it a little differently.

Edit: Adding sources...

Oghaito et al 2021 - https://gmd.copernicus.org/articles/14/1195/2021/ (ultimate source of the gridded model climate data I used)
https://esgf-node.ipsl.upmc.fr/search/cmip6-ipsl/ (where I accessed the gridded model climate data)
https://lipdverse.org/Temp12k/current_version/ (where I accessed peat and lake sediment samples)
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#2
It is always important to consider climate in migrations and an even bigger mistake to assume the climate of a said period was identical to that of today. That's why I think Davidski is barking up the wrong tree when he thinks R1a came from the east Baltic to Corded Ware. The east Baltic was a backwater in Corded Ware; with farming difficult, the people seem to have reverted to a hunter-gatherer, fisherman lifestyle. The finding of the R1a in Bulgaria is important, I think, because even though it may seem counter-intuitive to place R1a west of R1b at a period of time, I believe Podillya to be the ultimate source of R1a in Corded Ware and later Indo-European cultures.
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#3
wow, where did you get all this data?
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#4
Could you make similar graphs for the mountainous northeastern Caucasus, in particular Dagestan, from the Mesolithic to the Early Bronze Age, how conditions changed there
thank you in advance
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#5
(05-08-2024, 04:04 PM)Арсен Wrote: Could you make similar graphs for the mountainous northeastern Caucasus, in particular Dagestan, from the Mesolithic to the Early Bronze Age, how conditions changed there
thank you in advance

I do not have the ability (nor the resources) to run the simulations, I'm just plotting data (from https://esgf-node.ipsl.upmc.fr/search/cmip6-ipsl/, which houses data from a large number of climate studies) in a map, so unfortunately I can't select time-frames.

From my understanding, the main goal of the researchers who created the data I used is essentially to help calibrate climate models in order to simulate climate systems more accurately. It's part of the CMIP, a huge collaborative effort, and the paleoclimate (PMIP) side of things is just one part. Within these paleoclimate efforts, three of the main experiments include modeling the climate of the last glacial maximum (~127kya), the mid Holocene (~6kya), and the last millenium. It just happens that the mid Holocene experiment lines up with part of the Lazaridis paper. I think there are some studies that have modeled longer periods, but I haven't found that data yet. I will try to update things if I do find it, and can figure out how to use it.

Somewhat similarly, the peat and lake sediment samples (which I took from https://lipdverse.org/Temp12k/current_version/) are from discrete sites where academic studies were conducted. The closest samples to Dagestan are those from the northwest Caucasus I shared above, and they unfortunately only go back to 5500 ybp.
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#6
(05-08-2024, 04:42 PM)Cejo Wrote:
(05-08-2024, 04:04 PM)Арсен Wrote: Could you make similar graphs for the mountainous northeastern Caucasus, in particular Dagestan, from the Mesolithic to the Early Bronze Age, how conditions changed there
thank you in advance

I do not have the ability (nor the resources) to run the simulations, I'm just plotting data (from https://esgf-node.ipsl.upmc.fr/search/cmip6-ipsl/, which houses data from a large number of climate studies) in a map, so unfortunately I can't select time-frames.

From my understanding, the main goal of the researchers who created the data I used is essentially to help calibrate climate models in order to simulate climate systems more accurately. It's part of the CMIP, a huge collaborative effort, and the paleoclimate (PMIP) side of things is just one part. Within these paleoclimate efforts, three of the main experiments include modeling the climate of the last glacial maximum (~127kya), the mid Holocene (~6kya), and the last millenium. It just happens that the mid Holocene experiment lines up with part of the Lazaridis paper. I think there are some studies that have modeled longer periods, but I haven't found that data yet. I will try to update things if I do find it, and can figure out how to use it.

Somewhat similarly, the peat and lake sediment samples (which I took from https://lipdverse.org/Temp12k/current_version/) are from discrete sites where academic studies were conducted. The closest samples to Dagestan are those from the northwest Caucasus I shared above, and they unfortunately only go back to 5500 ybp.

I see, thanks anyway!
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