Historical co2 levels

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Historical CO2 Levels: A Comprehensive Overview

Introduction to Historical CO2 Levels

Understanding historical CO2 levels is crucial for comprehending the Earth's climate system and its changes over geological time. Atmospheric CO2 concentrations have varied significantly, influencing global temperatures and climate patterns. This article synthesizes research findings on CO2 levels from various geological periods, highlighting key trends and methodologies used to reconstruct past atmospheric conditions.

CO2 Levels in the Past 800,000 Years

Ice Core Data and Recent Trends

Ice core data provide a direct and continuous record of atmospheric CO2 levels over the past 800,000 years. These records show that pre-industrial CO2 levels ranged between 260 and 280 ppmv, with significant increases observed in the past two centuries due to industrial activities 25. The Mauna Loa Observatory has recorded a rise from 315 ppmv in 1958 to over 400 ppmv today, marking unprecedented levels in recent history .

Pleistocene Epoch CO2 Levels

Research using finely disseminated carbonates in paleosols from the Chinese Loess Plateau indicates that CO2 levels during the Pleistocene epoch (2.6–0.9 million years ago) were consistently below 300 ppmv. This suggests that the Earth has operated under low CO2 conditions for an extended period, with no significant changes across the mid-Pleistocene Transition .

CO2 Levels Over the Past 23 Million Years

Miocene to Quaternary Periods

A novel high-resolution CO2 record based on the δ13C value of terrestrial C3 plant remains reveals that CO2 levels ranged between 230 ppmv and 350 ppmv over the past 23 million years. The highest levels were observed during the early and middle Miocene, while the middle Pliocene experienced CO2 levels below present-day concentrations . This data underscores the significant deviation of current CO2 levels from long-established historical trends.

Middle Miocene Climatic Optimum

Studies using alkenone-pCO2 methodology and boron isotope-pH data indicate that CO2 levels during the Middle Miocene Climatic Optimum (17–14 million years ago) were between 400 and 500 ppmv. This period of global warmth was followed by a decline in CO2 during the Middle Miocene Climate Transition 89.

CO2 Levels Over the Past 60 Million Years

Early Cenozoic Era

Boron-isotope ratios of ancient planktonic foraminifer shells suggest that CO2 concentrations were over 2,000 ppmv during the late Paleocene and early Eocene (60–52 million years ago). A subsequent erratic decline in CO2 levels occurred between 55 and 40 million years ago, likely due to reduced volcanic outgassing and increased carbon burial .

Long-Term Trends

A comprehensive model of atmospheric CO2 over the past 570 million years indicates high CO2 levels during the Mesozoic and early Paleozoic, with significant reductions during the Permo-Carboniferous and late Cenozoic periods. These trends align with independently deduced paleoclimates, supporting the role of CO2 as a major climate control mechanism over geological timescales .

Conclusion

Historical CO2 levels have fluctuated widely, with significant implications for Earth's climate. From the high levels of the early Cenozoic to the low levels of the Pleistocene, these variations have been driven by natural processes such as volcanic activity, carbon burial, and weathering. Current CO2 levels, driven by anthropogenic activities, are unprecedented in recent geological history, highlighting the urgent need to understand and mitigate their impact on global climate.

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Most relevant research papers on this topic

A 23 m.y. record of low atmospheric CO2

Current atmospheric CO2 levels exceed the highest levels experienced since the Miocene, highlighting the disruption of long-established trends within Earth's atmosphere.

2020·

16citations

·Ying Cuiet al.

Geology

Evidence from polar ice cores for the increase in atmospheric CO2 in the past two centuries

The atmospheric CO2 concentration has increased from 250-290 p.p.m.v. preindustrial times to 345 p.p.m.v. today, with a new ice core from Siple Station providing valuable data for understanding the role of CO2 and climate sensitivity.

Highly Cited

1985·

627citations

·A. Neftelet al.

Nature

Historical greenhouse gas concentrations for climate modelling (CMIP6)

This study provides consolidated datasets of historical greenhouse gas concentrations for the CMIP6 project, focusing on the period 1850-2014 and including seasonality and latitudinal resolution.

Highly Cited

2016·

459citations

·M. Meinshausenet al.

Geoscientific Model Development

Atmospheric carbon dioxide concentrations over the past 60 million years

Atmospheric carbon dioxide concentrations were higher in the early Cenozoic era, but have stabilized since the early Miocene, with reduced CO2 outgassing and increased carbon burial contributing to the decline.

Highly Cited

2000·

1708citations

·P. Pearsonet al.

Nature

Evidence of changing concentrations of atmospheric CO2, N2O and CH4 from air bubbles in Antarctic ice

Antarctic ice measurements reveal that atmospheric CO2, N2O, and CH4 concentrations have increased by 90 and 8% since 1600, with the latter likely due to expanding anthropogenic combustion processes.

Highly Cited

1986·

204citations

·G. Pearmanet al.

Nature

Low CO2 levels of the entire Pleistocene epoch

Low CO2 levels (300 ppm) were observed throughout the Pleistocene interglacials, suggesting CO2 was not the driver of this important climate change event.

2019·

42citations

·Jiawei Daet al.

Nature Communications

Warm climate under high CO2 level in the early Pleistocene based on a leaf fossil assemblage in central Japan

High CO2 levels during the early Pleistocene led to a warm climate with a mean annual temperature of 11.0 degrees C, highlighting the vital role of CO2 in controlling early Pleistocene interglacial temperature.

2018·

6citations

·Yuqing Wanget al.

Review of Palaeobotany and Palynology

A 40-million-year history of atmospheric CO2

The new pCO2 record from Ocean Drilling Program Site 925 suggests that atmospheric CO2 levels were highest during the Middle Miocene Climatic Optimum, followed by a decline during the Middle Miocene Climate Transition.

Highly Cited

2013·

443citations

·Yi Ge Zhanget al.

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

Atmospheric CO2 estimates for the Miocene to Pleistocene based on foraminiferal δ11B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific

Ocean Drilling Program Sites 806 and 807 provide valuable data on atmospheric CO2 levels during major climate transitions, supporting a coupling between CO2, temperature, and ice sheet expansion over the past 17 million years.

2021·

10citations

·M. Guillermicet al.

Climate of the Past

Atmospheric Carbon Dioxide Levels Over Phanerozoic Time

Atmospheric carbon dioxide levels were high during the Mesozoic and early Paleozoic and low during the Permo-Carboniferous and late Cenozoic, supporting the greenhouse effect on climate over long time scales.

Highly Cited

1990·

566citations

·R. Berner

Science

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