I’m going to admit to a healthy skepticism about this conclusion from scholars at University College London reported by the BBC:
Colonisation of the Americas at the end of the 15th Century killed so many people, it disturbed Earth’s climate.
That’s the conclusion of scientists from University College London, UK.
The team says the disruption that followed European settlement led to a huge swathe of abandoned agricultural land being reclaimed by fast-growing trees and other vegetation.
This pulled down enough carbon dioxide (COâ‚‚) from the atmosphere to eventually chill the planet.
It’s a cooling period often referred to in the history books as the “Little Ice Age” – a time when winters in Europe would see the Thames in London regularly freeze over.
“The Great Dying of the Indigenous Peoples of the Americas led to the abandonment of enough cleared land that the resulting terrestrial carbon uptake had a detectable impact on both atmospheric COâ‚‚ and global surface air temperatures,” Alexander Koch and colleagues write in their paper published in Quaternary Science Reviews.
Let’s assume that their estimates of the pre-Columbian population of the Americas is correct. That’s by no means a given. Estimates have been everywhere from 10 million to 100 million or thereabouts. But let’s assume it anyway. That means that 55 million people died over the course of a century.
That’s just about how many people died from 1930 to 1960 due to the activities of Stalin, Hitler, and Mao. If the consequences of that many deaths had so great an impact on the climate, wouldn’t that throw all of the climate models off?
I would also think that we would find a lot more remains than have been found but that’s another story.
You could just as well blame climate change on the invention of the carbonated soft drink.
And this story nicely illustrates how far researchers have to bend over to the Climate Change Industry to get their study funded. Plus paying homage to the same is the sure path to tenure.
As to the ‘nother story, I’m sure there were some tens of millions of Natives in the “new world”, but 80-100 M seems incompatible with estimates of 80 M bison on the plains. Just as stories of lands teeming with game and rivers so thick with fish you could walk across on their backs are incompatible with the journals of Lewis and Clark. (They almost starved.)
Via Wikepedia, the Black death killed 75 to 100 million Europeans in the last half of the 14th century. We know that some of the improved farmland in the UK was not brought back to agricultural use until WW2. More death and destruction if we look at Eurasia overall.
Granted large margin of errors, I think 40 million Americans before Columbus. (Henige, “Numbers from Nowhere”) A lot of uncertainty has to with a lot of variability in lifestyles, with central Mexico perhaps having 5 to 10 million people, making it one of the most dense places on earth, while places like the Great Plaines had less intensive habitation and farming.
That’s another example that is probably not factored into the climate models.
That would not be surprising. Consider the yields of the various grain crops:
You can feed more people per acre cultivated with corn or rice than with wheat, barley, or oats.
It has been a while since I read about it, but at that time, the leading cause of the Little Ice Age was believed to be a disruption in the Gulf Stream. If I remember correctly, the output from the St. Lawrence River got blocked, and the Gulf Stream was not able to deliver warm water to the north.
“That’s just about how many people died from 1930 to 1960 due to the activities of Stalin, Hitler, and Mao. If the consequences of that many deaths had so great an impact on the climate, wouldn’t that throw all of the climate models off?”
Did those deaths result in a lot of cleared land going back to forests? I dont think so. The point is that it is not the deaths per se but the loss of cleared lands that resulted in a drop in CO2.
Absent access to the original article, not given at your link, I would assume that as pointed out late in your article, that the Little Ice Age is still seen as multi-factorial, and this research is just offering an explanation for the drop in CO2. So if you use PDs example, you may be lacking the other components besides a drop in CO2.
“Ed Hawkins, professor of climate science at Reading University, was not involved in the study. He commented: “Scientists understand that the so-called Little Ice Age was caused by several factors – a drop in atmospheric carbon dioxide levels, a series of large volcanic eruptions, changes in land use and a temporary decline in solar activity.”
It helps to read the entire article. It also claims that the article estimated 60 million people,
Steve
It should be understood human respiration is part of the carbon cycle, and not a net CO2 contributor. Steve is correct the determining factor here is land-use changes, which are factored into all climate models.
It has been suggested the activity of land animals in the Triassic and Jurassic cleared vast areas of plant life and contributed to elevated CO2 of the time.
“It should be understood human respiration is part of the carbon cycle, and not a net CO2 contributor.”
You do understand that the essence of the claim is that in the biological carbon cycle the re-uptake of CO2 by newly prosperous land began growing plants, trees, crops etc which raced ahead of CO2 emission. As the biological CO2 cycle is 1000 greater that the ecological cycle the claim is that almost by definition human respiration was a newly influential net contributor.
Be that as it may, what I really want to know is what the exercise, dietary and magic elixir regimens of these scientists was that they could have been born way back then, taken such excellent and accurate measurements so as to quantify this, and still be alive to write about it.
Human respiration is entirely accounted for in the carbon cycle. It cannot build up, which is why it’s called a carbon cycle.
Ironically, there is a fierce debate in the scientific community about the actual effects of forests. Specifically, the climate benefits of carbon uptake by trees can be counteracted by the albedo of trees.
https://www.nature.com/articles/d41586-019-00122-z
As far as this particular study, I haven’t been able to find it either, but it appears to be part of an explanation for the measured drop in CO2 at that time (as determined from ice cores). The drop was small and, from what I understand, not enough to, by itself, cause the little ice age. How big a factor it was is speculation.
So this is yet another example of the media sensationalizing and mis-reporting science – or at least burying the lede near the end.