texas a&m study: humankind never co-existed with a high-carbon-dioxide atmosphere until 1965 texas a&m oceanographys yige zhang co-authored a new study that shows earths carbon dioxide atmospheric concentrations averaged 230 parts per million for 25 million years; todays levels are about 410 parts per million sep 25 2019the loess plateau in central china researchers analyzed soil carbonates from the plateau to quantify ancient atmospheric carbon dioxide levels (photo courtesy of jiawei da nanjing university)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 25 million years of the pleistocene era carbon dioxide concentrations averaged 230 parts per million todays levels are more than 410 parts per million in 1965 earths carbon dioxide atmospheric concentrations exceeded 320 parts per million a high-point never reached in the past 25 million years this study shows according to this research from the first homo erectus which is currently dated to 21–18 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 its also an experiment for us for ourselves he said carbon dioxide is a greenhouse gas that contributes to the warming of earths atmosphere and is considered a driver of global climate change zhang explained its 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 earths 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 ancient soil reveals millions of years of data the scientists analyzed soil carbonates from the loess plateau in central china to quantify ancient atmospheric carbon dioxide levels as far back as 25 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 earths carbon dioxide levelsdr yige zhangthe loess plateau in central china (photo courtesy of jiawei da nanjing university)the loess plateau is an incredible place to look at aeolian 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 universitys jiawei da reconstructing a carbon dioxide history for clues about our future 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 todays carbon-dioxide levels is yet to be seen by leslie lee '09