A new paper claims that the die-off of indigenous Americans in the sixteenth century after colonization caused the Little Ice Age.
I’m skeptical.
[Update a while later]
A response to a query to Judith Curry.
Just spotted this. Its an interesting hypothesis, but a global impact seems a bit far fetched
— Judith Curry (@curryja) January 31, 2019
Carried to its logical conclusion, I predict the Left calling for genocidal wars to fight global warming. Not like they don’t have a history of this sort of thing with Mao’s awesome agricultural plans, Stalin’s famines, and Pol Pot’s killing fields.
Yet, the Black Death caused no such disruption. Can we say cum hoc ergo propter hoc?
The authors fail to address the increase in carbonyl sulfide reported on by Rubino, et al three years ago.
https://www.nature.com/articles/ngeo2769
You can’t have a flush of new growth and an increase in COS. Something caused a decrease in photosynthesis which resulted in the change in CO2.
Sounds fishy. A lot of forested land when native Americans arrived was under ice or transitioning. Why wouldn’t the explosion of growth after the ice sheets retreated have caused glaciation to return? It seems that our climate would be even more chaotic than it is now if such a small change could have such a large impact. What about forest or grassland fires?
Earlier today I’d left a link to the story in a comment at Judith Curry’s blog, along with a mention of David Henige’s book “Numbers from Nowhere: The Native American Pre-Contact Population Debate.” He puts forth a wide array of well-reasoned arguments against the “high counters”, which indulge themselves with bad data, unreliable sources, bad math, and circular reasoning. As he argues, the pre-contact population is probably not discoverable by any archaeological or historical method.
There was a recent paper that used a different technique, looking for signs of population bottle-necks in the DNA of Native Americans by looking at lineage diversity. They found signs of one, but they thought it occurred somewhere around 1000 AD.
I’ve long been fascinated by the wide range of estimates of pre-Columbian native American populations. I’ve seen figures as high as 60 million for South and Central America, 5 million for what is now the United States, and 2 million for what is now Canada.
These are highs, but I have also heard numbers as low as 100,000 for all of North America. Who to believe?
Compare Europe in 1492 (population 60 million) with the high estimate for South America (60 million). South America’s land area is 6.888 million square miles, while Europe’s is 3.93 million square miles, for a ratio of 1.75:1. So the population densities would be within an order of magnitude.
But Europeans of that age had one thing the Native Americans did not: several modes of transportation, and the one that was roughly equivalent to the automobile was the horse. Native Americans moved around on foot, or by boat – that’s it. People on foot can only move a certain distance per day, AND perform the work required to stay alive (hunting, fishing, gathering, and performing whatever limited agriculture they practiced). I don’t know what the limits to “sustainable” populations are with only foot transportation, but I imagine they are far less than the high numbers.
In any event, the disappearance of 67 million people who didn’t have that big of an effect on their environment is unlikely to cause any kind of detectable drop in atmospheric CO2. I mean, an estimated 50 million people died of the Spanish Flu in 1919, right after 37 million being killed in WWI. We didn’t have much of an Ice Age after that.
Well, as Hinige noted, some of the methods used to arrive at the estimates are exactly the same as the methods used to estimate the number of Orcs in Middle Earth. For example, taking an unreliable population estimate of a village (a guess found in some adventurer’s letter), a guess as to how much land area it took to feed the village, and then a guess as to how many such villages there could have been in the X square miles of the region. The method doesn’t work because travelers only wrote about a village they found, so there might have been three similar ones or thirty thousand similar ones. It’s just up to the imagination.
The disease method is different, and circular. That argument is that the original population O was reduced to a surviving population S by a disease which had a lethality rate of L=(O-S)/O, or a survival rate of S/O. How do they know the original population was O? Because the rough population count that finally shows up in a record is S, and the survival rate of the imagined disease L, let’s them calculate it. But L was calculated based on O and S, which were based on L.
Smallpox is often blamed, and Jared Diamond won a Pulitzer advancing the notion that Europeans brought diseases that they’d developed herd immunity to, specifically smallpox. There are major flaws in his argument.
One is that European have zero immunity to smallpox to this day. That’s why the DoD freaked out about it after 9/11.
Another is that herd immunity means enough people have gotten the disease (with the usual percentage of deaths it inflicts) that outbreaks are less common among the surviving population. That would also happen with Indians. Europe went through this, yet didn’t depopulate.
Another reason Europeans wouldn’t have had herd immunity is that recent DNA analysis finds that smallpox first appeared in Europe sometime between 1588 and 1645. National Geographic story. That means the early Spanish explorers couldn’t have brought smallpox to the New World because they had never been exposed to it. No European had. That also means that Europeans couldn’t have had herd immunity, and were just as much “virgin soil” for it as the Native Americans.
Anything to reroute the Narrative around inconvenient truths, as in, now that the next grand minumum has arrived on schedule and will smother AGW, even if it exists, find something else to blame.
The one reasonably well documented New World population collapse, Mexico in the 16th century, appears to have been due to salmonella carried by pigs, Norwegian rats, European house mice, and maybe Eurasian dogs, in the context of sanitation degradation due to a long-lasting drought in Mexico. There was a measles epidemic in the middle of all this, which hardly makes a blip on the population collapse graph. You can make a start at the Wiki article, though I’d be quick as these are being edited away quickly.
https://en.wikipedia.org/wiki/Cocoliztli_Epidemic_of_1545-1548
That’s one still intact article. Others have been edited down to be called “questionable.” It’s a start for the curious.
A Harvard trained Mexican epidemiologist thinks that outbreak was a native virus, a hemorrhagic fever spread by rodents, and was linked to the end of severe drought conditions in Mexico City.
CDC.gov article
The disease kept making reappearances (ten plagues in all) but hasn’t caused trouble since the mid-1600’s. I figure that maybe the European domestic cats killed off the right rodents.