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Until 1965, humans have lived in low-CO2 environment: Researchers

ANI | Updated: Sep 28, 2019 18:36 IST

Washington D.C. [USA], Sept 28 (ANI): While the world is already grappling with climate change, a new study has pointed out another startling fact.
Human have inhabited this planet for millions of years but have never lived with the high carbon-dioxide atmospheric conditions that have become the norm on Earth in the last 60 years, the study stated.
Titled 'Low CO2 levels of the entire Pleistocene Epoch' and published in the journal Nature Communications, it highlighted that 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 co-author on the study Dr. Yige Zhang, 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 added.
"It's important to study atmospheric CO2 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.
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. The earliest identified dust on that plateau is from 22 million years ago. So, it has extremely long records," Zhang said.
"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. (ANI)

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