Science Forums 2

[Essay]

I think the oceans and lands are about equivalent in CO2 cycling abilities; with most of the oceans being a "desert" for life--coastal waters being the main productive areas.

...and the oceans remained mostly as a constant in equation of CO2 balance--until the industrial age. I was focusing on the land-based contribution to CO2 balance as the factor being strongly influenced by civilization; with the Amazon being a prime example.
Being the fastest growing forests, they may have drawn down the most CO2 after the American civilizations collapsed.

It's something like 100 billion tons of carbon dioxide exchanged by the lands each year. If globally, or even regionally at various times through history, we shifted that balance by just 2-3 billion tons/year, then climate could be influenced over the course of decades or longer--assuming CO2 does act as a fine-tuning thermostat. After a large collapse the shift could be 5-10 billion tons/year, for decades or even a century or longer.

The point of this thread seems to be that globally there was a large collapse in many civilizations around 1500--the transition between the MWP & LIA--especially the intensively agrarian New World civilizations that seem to have cultivated two continents.