The Amazon and global warming

[lemit]

I recently heard a theory that intrigues me:

The Amazon basin was populated by millions in highly developed cultures and technologies until the end of the Fifteenth Century, in other words, during the Medieval Warm Period.

When the native cultures died and the forests reclaimed the Amazon, we entered the Little Ice Age.

Now, accelerated destruction of the Amazon forests and the acceleration of global warming seem to coincide.

That's the logic. Can anybody tell me what the science says?

Thanks.

--lemit

[lemit]

Also, I have long considered the Amazon to be the third pole or the fifth ocean in its influence on climate. That's why I was thrilled to hear this theory.

Are there other areas that might compete for the designation of third pole? Fifth ocean? I know about the Antarctic. For this discussion, it's a redundancy.

--lemit

[Moontanman]

I'm not sure about a third pole but check out this link for the connection with the plague.

Way of the Woo: The Pandemic vs. The Maunder Minimum

[Essay]

Very cool idea! Well, I should say a hot idea and a cool link! Thanks MTM!!!

While I like the implications of the article, it places the LIA from 1250-1650. I thought the LIA was more like wiki says: "Some confine the Little Ice Age to approximately the 16th century to the mid 19th century. It is generally agreed that there were three minima, beginning about 1650, about 1770, and 1850, each separated by slight warming intervals."

Implications: Massive collapses of local civilizations due to population collapses, from the 1350's to the 1650's may have led to a large drawdown of CO2 as jungles, forests and animal herds burgeoned--and nobody remained to manage the herds, burn off the underbrush and litter, and clear/cultivate the lands. This applies to all of the Americas (and Europe), but maybe Africa and Asia too.

I thought the MWP was from 800-1500. This would coincide with when the lands were being intensively managed--20 million Incas, Cahokia, etc.--releasing CO2.

Well, I was close: wiki says, "The Medieval Warm Period was a time of warm weather around AD 800-1300 during the European Medieval period."

p.s. wiki says: "Cahokia is the site of an ancient Native American city (650-1400 CE) near Collinsville, Illinois in the American Bottom floodplain, across the Mississippi River from St. Louis, Missouri. The 2,200-acre (8.9 km2) site includes at least 109 man-made earthen mounds. Cahokia Mounds is the largest archaeological site related to the Mississippian culture, which developed advanced societies in eastern North America centuries before the arrival of Europeans."

p.p.s. I did not know this, but wiki also says: "The plague resurfaced in the mid-18th century; like the Black Death, the Third Pandemic began in Central Asia. It spread worldwide, killing millions, into the early 20th century."

[lemit]

Now I'm confused. I'd always heard that the Little Ice Age started in the Fifteenth Century and finally disappeared in the late Nineteenth Century. I think that has been demonstrated.

So, what about the importance of the Amazon to the world's climate? That's still the essential question.

--lemit

[Essay]

Originally Posted by lemit

So, does that mean the Amazon isn't as important to the earth's climate as I thought it was or just that the specific theory is questionable, or neither?

I think it lends support to the idea that humans have been affecting the climate for over a millinneum; we're just affecting it much more in the 20th century and now.

[Essay]

Originally Posted by from MTM's link

Now, another contender has entered the arena, vying for its place in history as the cause of the Little Ice Age: the pandemic. Richard Nevle and Dennis Bird of Stanford have examined sediment cores and soil samples dating back 5000 years and noted a precipitous drop in charcoal ash following periods of major pandemics. This indicated a massive decrease in the clearing of forests by burning to create more land for crops. While the population recovered (remember, Europe lost 20-30 million people in the span of six years), abandoned land began to regrow. Whole new forests sprouted, sucking CO2 out of the atmosphere, effectively removing layers from the Earth's thermal blanket. Moreover, their data aligns nearly perfectly (or so they say) with other information (heavy/light carbon isotope ratios) detailing the drop in atmospheric CO2 at the same time.

This (above) is the point that I thought was supporting.

I think the dates for LIA in that link are way off, though.
But with the correct dates, it supports the idea even more--though I'm not sure "how" their data lines up with "which" dates....
...or words to that effect.

[engineerdude]

Don't the world's oceans, which cover 70% of our planet, soak up the vast majority of planetary CO2? There's many articles that discuss this, but here's one:

Carbon dioxide: where does it all go? | Science News | Find Articles at BNET

Don't get me wrong I think the Amazon is cool and all, but as far as being a CO2 sink it isn't very significant.

[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.

[engineerdude]

Originally Posted by 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.

I find this collapse of civilizations around 1500 intriguing as well - but I seriously doubt it has anything to do with CO2. Perhaps there is something that both causes large-scale disruptions and also causes a change in CO2 levels, but I do not see how the Amazon can have anything to do with it, at least not directly.

To explain, look at this:

total biomass of all land plants: 1.25 billion tons
total biomass of blue-green algae in oceans: 44 billion tons

Far from being a "desert" of life, the oceans contain 97.2% of all the plant life on our planet, by mass.

The blue-green algae (cyanobacteria) are what gave us our current atmosphere starting 2.8 billion years ago, and they continue, through sheer volume, to say what happens in our air.

Here's a nice article on cyanobacteria:

Cyanobacteria - Wikipedia, the free encyclopedia