New World Settlement -> Little Ice Age?

[Jimmy Higgins]

A paper is out that ponders the influence the changes in the New World had regarding the Little Ice Age.

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 (CO₂) from the atmosphere to eventually chill the planet.

As a reminder, this is a paper, not professional consensus.

 

[skepticalbip]

As a reminder, this is a paper, not professional consensus.

...That reminder should be stressed...

I find it telling that the paper ignored that the Maunder Minimum coincides with the period of the little ice age. It is well established that solar activity effects global temperature and throughout the Maunder Minimum there was little to no sunspot activity.

 

[bigfield]

As a reminder, this is a paper, not professional consensus.

...That reminder should be stressed...

I find it telling that the paper ignored that the Maunder Minimum coincides with the period of the little ice age. It is well established that solar activity effects global temperature and throughout the Maunder Minimum there was little to no sunspot activity.


View attachment 19953

They do address the Maunder Minimum and the Sporer Minimum: they say it doesn't correlate with global temperatures during the coldest part of the LIA. See page 27.

 

[skepticalbip]

As a reminder, this is a paper, not professional consensus.

...That reminder should be stressed...

I find it telling that the paper ignored that the Maunder Minimum coincides with the period of the little ice age. It is well established that solar activity effects global temperature and throughout the Maunder Minimum there was little to no sunspot activity.


View attachment 19953

They do address the Maunder Minimum and the Sporer Minimum: they say it doesn't correlate with global temperatures during the coldest part of the LIA. See page 27.

I was addressing the article linked in the OP. I didn't see a link to study paper. I still don't but maybe that is my oversight.

The OP link:

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

America colonisation ‘cooled Earth's climate’

etc. etc.

I only saw a brief allusion to sun spots but it was then dropped. It was a quote by someone not involved in the study. (perhaps a reviewer criticizing the study?)

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.

The linked article focused on changes in land use and CO2 and I saw no mention of volcanism or sun spot activity.

 

[lpetrich]

The Little Ice Age was anthropogenic? by PZ Myers -- where I learned of this hypothesis, referring to
America colonisation ‘cooled Earth's climate’ - BBC News, referring to
Earth system impacts of the European arrival and Great Dying in the Americas after 1492 - ScienceDirect (open access)

The paper's abstract:

Human impacts prior to the Industrial Revolution are not well constrained. We investigate whether the decline in global atmospheric CO2 concentration by 7–10 ppm in the late 1500s and early 1600s which globally lowered surface air temperatures by 0.15∘C, were generated by natural forcing or were a result of the large-scale depopulation of the Americas after European arrival, subsequent land use change and secondary succession. We quantitatively review the evidence for (i) the pre-Columbian population size, (ii) their per capita land use, (iii) the post-1492 population loss, (iv) the resulting carbon uptake of the abandoned anthropogenic landscapes, and then compare these to potential natural drivers of global carbon declines of 7–10 ppm. From 119 published regional population estimates we calculate a pre-1492 CE population of 60.5 million (interquartile range, IQR 44.8–78.2 million), utilizing 1.04 ha land per capita (IQR 0.98–1.11). European epidemics removed 90% (IQR 87–92%) of the indigenous population over the next century. This resulted in secondary succession of 55.8 Mha (IQR 39.0–78.4 Mha) of abandoned land, sequestering 7.4 Pg C (IQR 4.9–10.8 Pg C), equivalent to a decline in atmospheric CO2 of 3.5 ppm (IQR 2.3–5.1 ppm CO2). Accounting for carbon cycle feedbacks plus LUC outside the Americas gives a total 5 ppm CO2 additional uptake into the land surface in the 1500s compared to the 1400s, 47–67% of the atmospheric CO2 decline. Furthermore, we show that the global carbon budget of the 1500s cannot be balanced until large-scale vegetation regeneration in the Americas is included. The Great Dying of the Indigenous Peoples of the Americas resulted in a human-driven global impact on the Earth System in the two centuries prior to the Industrial Revolution.