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Author Topic: America colonisation ‘cooled Earth's climate’  (Read 236 times)

kassy

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America colonisation ‘cooled Earth's climate’
« on: January 31, 2019, 01:20:40 PM »
Colonisation of the Americas at the end of the 15th Century killed so many people, it disturbed Earth's climate.

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"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 CO₂ and global surface air temperatures," Alexander Koch and colleagues write in their paper published in Quaternary Science Reviews.

...

What does the study show?
The team reviewed all the population data it could find on how many people were living in the Americas prior to first contact with Europeans in 1492.

It then assessed how the numbers changed in following decades as the continents were ravaged by introduced disease (smallpox, measles, etc), warfare, slavery and societal collapse.

It's the UCL group's estimate that 60 million people were living across the Americas at the end of the 15th Century (about 10% of the world's total population), and that this was reduced to just five or six million within a hundred years.

The scientists calculated how much land previously cultivated by indigenous civilisations would have fallen into disuse, and what the impact would be if this ground was then repossessed by forest and savannah.

The area is on the order of 56 million hectares, close in size to a modern country like France.

This scale of regrowth is figured to have drawn down sufficient CO₂ that the concentration of the gas in the atmosphere eventually fell by 7-10ppm (that is 7-10 molecules of CO₂ in every one million molecules in the air).

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There is a marked cooling around that time (1500s/1600s) which is called the Little Ice Age, and what's interesting is that we can see natural processes giving a little bit of cooling, but actually to get the full cooling - double the natural processes - you have to have this genocide-generated drop in CO₂."

lots more on:
https://www.bbc.com/news/science-environment-47063973

paper:
https://www.sciencedirect.com/science/article/pii/S0277379118307261

I find this really interesting because i always had a hunch this played a role (there are older papers on the effects of the black death had on reforestation).

El Cid

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Re: America colonisation ‘cooled Earth's climate’
« Reply #1 on: January 31, 2019, 01:42:05 PM »
I read about this before. It is plausible, although there is a significant disagreement about the number of people who died during the conquest of the Americas