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Humankind did not live with a high-carbon dioxide atmosphere until 1965

#1
C C Offline
https://today.tamu.edu/2019/09/25/humank...ntil-1965/

RELEASE: Humans have never before lived with the high carbon-dioxide atmospheric conditions that have become the norm on Earth in the last 60 years, according to a new research study. Titled "Low CO2 levels of the entire Pleistocene Epoch" and published in Nature Communications today, the study shows that for the entire 2.5 million years of the Pleistocene era, carbon dioxide concentrations averaged 230 parts per million.

Today's levels are more than 410 parts per million. In 1965, Earth's carbon dioxide atmospheric concentrations exceeded 320 parts per million, a high-point never reached in the past 2.5 million years, this study shows. "According to this research, from the first Homo erectus, which is currently dated to 2.1-1.8 million years ago, until 1965, we have lived in a low-carbon-dioxide environment -- concentrations were less than 320 parts per million," said Dr. Yige Zhang, a co-author of the research study and an assistant professor in the Department of Oceanography, in the College of Geosciences, at Texas A&M University. "So, this current high-carbon-dioxide environment is not only an experiment for the climate and the environment -- it's also an experiment for us, for ourselves," he said.

Carbon dioxide is a greenhouse gas that contributes to the warming of Earth's atmosphere and is considered a driver of global climate change, Zhang explained. "It's important to study atmospheric CO2 (carbon dioxide) concentrations in the geological past, because we know that there are already climate consequences and are going to be more climate consequences, and one way to learn about those consequences is to look into Earth's history," he said. "Then we can see what kind of CO2 levels did we have, what did the climate look like, and what was the relationship between them."

Mr. Jiawei Da, Dr. Xianqiang Meng, and Dr. Junfeng Ji, all of Nanjing University in China; and Dr. Gen Li, of the California Institute of Technology, co-authored the research. The scientists analyzed soil carbonates from the Loess Plateau in central China, to quantify ancient atmospheric carbon dioxide levels, as far back as 2.5 million years ago. Climate scientists often use ice cores as the 'gold standard' in physical climate records, Zhang said, but ice cores only cover the past 800,000 years.

Analyzing pedogenic carbonates found in the ancient soil, or paleosols, from the Loess Plateau, the scientists reconstructed the Earth's carbon dioxide levels "The Loess Plateau is an incredible place to look at Eolian, or wind, accumulation of dust and soil," Zhang said. "The earliest identified dust on that plateau is from 22 million years ago. So, it has extremely long records. The layers of loess and paleosol there contain soil carbonates that record atmospheric carbon dioxide, if we have very careful eyes to look at them."

"Specifically, carbonates formed during soil formation generally reach carbon isotopic equilibrium with ambient soil CO2, which is a mixture of atmospheric CO2 and CO2 produced by soil respiration. Through the application of a two-component mixing model, we can reconstruct paleo-CO2 levels using carbonates in fossil soils," said Nanjing University's Jiawei Da.

Using those materials and the techniques, the researchers constructed a carbon dioxide history of the Pleistocene."Our reconstructions show that for the entire Pleistocene period, carbon dioxide averaged around 230 parts per million, which is the same as the last 800,000 years' values," Zhang said. "Our paleosol-based CO2 estimates are in line with snapshots of early-Pleistocene CO2 retrieved from Antarctic old, blue ice, suggesting that the Earth system has been operating under low CO2 levels throughout the Pleistocene," said Dr. Junfeng Ji of Nanjing University.

"We evolved in a low-carbon-dioxide environment," Zhang said, and how humans will evolve and be affected by today's carbon-dioxide levels is yet to be seen.
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#3
billvon Offline
(Sep 25, 2019 10:16 PM)C C Wrote: "We evolved in a low-carbon-dioxide environment," Zhang said, and how humans will evolve and be affected by today's carbon-dioxide levels is yet to be seen.
No we didn't.  We've been sleeping inside for at least 10,000 years.
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#4
C C Offline
(Sep 25, 2019 11:04 PM)confused2 Wrote: Given that exhaled air is about 40,000 ppm CO2 a difference between 230ppm and 410ppm in the incoming air is unlikely to be significant. Sleeping in a closed room (not normally fatal):-
https://vair-monitor.com/2016/09/29/slee...2-analyze/

(Sep 26, 2019 02:23 AM)billvon Wrote:
(Sep 25, 2019 10:16 PM)C C Wrote: "We evolved in a low-carbon-dioxide environment," Zhang said, and how humans will evolve and be affected by today's carbon-dioxide levels is yet to be seen.

No we didn't.  We've been sleeping inside for at least 10,000 years.

There's no mention of human beings in the original paper or the year 1965 (that I can find). The connection to current climate change seems to boil down to: "Quantifying ancient atmospheric pCO2 provides valuable insights into the interplay between greenhouse gases and global climate...". Which is similarly expressed in the article: "...one way to learn about those consequences is to look into Earth’s history,” Zhang said. “Then we can see what kind of CO2 levels did we have, what did the climate look like, and what was the relationship between them.”"

There's no source given by the (Texas A&M) article for the quotes in the article. Since he's an assistant professor there, I guess we're to assume those from Zhang came from statements, lectures, or interviews he's made on campus or elsewhere. Apparently we're left to fill in the blank that the shift and emphasis in Zhang's public talks to people -- and our not evolving in an overall Earth environment with general atmospheric conditions like the current one -- comes from academic prodding to attach something politically relevant or politically decorative to the research.
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