Solar luminosity on the early Earth was significantly lower than today. Therefore, solar luminosity models suggest that, in the atmosphere of the early Earth, the concentration of greenhouse gases such as carbon dioxide and methane must have been much higher1,2. However, empirical estimates of Proterozoic levels of atmospheric carbon dioxide concentrations have not hitherto been available. Here we present ion microprobe analyses of the carbon isotopes in individual organic-walled microfossils extracted from a Proterozoic (∼ 1.4-gigayear-old) shale in North China. Calculated magnitudes of the carbon isotope fractionation in these large, morphologically complex microfossils suggest elevated levels of carbon dioxide in the ancient atmosphere—between 10 and 200 times the present atmospheric level. Our results indicate that carbon dioxide was an important greenhouse gas during periods of lower solar luminosity, probably dominating over methane after the atmosphere and hydrosphere became pervasively oxygenated between 2 and 2.2 gigayears ago.
This is a preview of subscription content
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Kasting, J. F. Earth's early atmosphere. Science 259, 920–926 (1993)
Pavlov, A. A., Hurtgen, M. T., Kasting, J. F. & Arthur, M. A. Methane-rich Proterozoic atmosphere? Geology 31, 87–90 (2003)
Xiao, S., Knoll, A. H., Kaufman, A. J., Yin, L. & Zhang, Y. Neoproterozoic fossils in Mesoproterozoic rocks? Chemostratigraphic resolution of a biostratigraphic conundrum from the North China Platform. Precambr. Res. 84, 197–220 (1997)
Brasier, M. D. & Lindsay, J. F. A billion years of environmental stability and the emergence of eukaryotes: New data from northern Australia. Geology 26, 555–558 (1998)
Javaux, E. J., Knoll, A. H. & Walter, M. R. Morphological and ecological complexity in early eukaryotic ecosystems. Nature 412, 66–69 (2001)
Shively, J. M. & Barton, L. L. Variations in Autotrophic Life 1–346 (Academic, New York, 1991)
Schulz, H. et al. Dense populations of a giant sulfur bacterium in Namibian shelf sediments. Science 284, 493–495 (1999)
Cristy, S. S. in Inorganic Mass Spectrometry (eds Barshick, C.M., Duckworth, D.C. & Smith, D.H.) 159–221 (Marcel Dekker, New York, 2000)
House, C. H. et al. Carbon isotope composition of individual Precambrian microfossils. Geology 28, 707–710 (2000)
Ueno, Y., Isozaki, Y., Yurimoto, H. & Maruyama, S. Carbon isotopic signatures of individual Archean microfossils(?) from Western Australia. Int. Geol. Rev. 43, 196–212 (2001)
Hayes, J. M., Strauss, H. & Kaufman, A. J. The abundance of C-13 in marine organic matter and isotopic fractionation in the global biogeochemical cycle of carbon during the past 800 Ma. Chem. Geol. 16, 103–125 (1999)
Laws, E. A., Popp, B. N., Bidigare, R. R., Kennicutt, M. C. & Macko, S. A. Dependence of phytoplankton carbon isotopic composition on growth rate and [CO2(aq)]: Theoretical considerations and experimental results. Geochim. Cosmochim. Acta 59, 1131–1138 (1995)
Laws, E. A., Bidigare, R. R. & Popp, B. N. Effect of growth rate and CO2 concentration on carbon isotopic fractionation by the marine diatom Phaeodactylum tricornutum. Limnol. Oceanogr. 42, 1552–1560 (1997)
Popp, B. N. et al. Effect of phytoplankton geometry on carbon isotopic fractionation. Geochim. Cosmochim. Acta 62, 69–77 (1998)
Bidigare, R. R. et al. Consistent fractionation of C-13 in nature and in the laboratory: Growth-rate effects in some haptophyte algae. Glob. Geochem. Cycles 13, 251–252 (1999)
Knoll, A. H. Microbiotas of the late Precambrian Hunnberg Formation, Nordaustlandet, Svalbard. J. Paleontol. 58, 131–162 (1984)
Grotzinger, J. P. & Kasting, J. F. New constraints on Precambrian ocean composition. J. Geol. 101, 235–243 (1993)
Rye, R., Kuo, P. H. & Holland, H. D. Atmospheric carbon-dioxide concentrations before 2.2-billion years ago. Nature 378, 603–605 (1995)
Holland, H. D. in Early Life on Earth (ed. Bengtson, S.) 237–244 (Columbia Univ. Press, New York, 1994)
Karhu, J. & Holland, H. Carbon isotopes and the rise of atmospheric oxygen. Geology 24, 867–870 (1996)
Habicht, K. S., Gade, M., Thamdrup, B., Berg, P. & Canfield, D. E. Calibration of sulfate levels in the Archean oceans. Science 298, 2372–2374 (2002)
Farquhar, J., Hauri, E. & Wang, J. New insights into carbon fluid chemistry and graphite precipitation: SIMS analysis of granulite facies graphite from Ponmudi, South India. Earth Planet. Sci. Lett. 171, 607–621 (1999)
We thank the following for technical assistance; E. Hauri, J. Wang, J. Orloff, R. Dotson, K. Livi, D. Veblen and P. Piccoli. We also thank A. Knoll and L. Yin for providing samples for bulk rock analyses, and J. Hayes for comments on an earlier version of this manuscript. This research was supported by NASA Exobiology, NSF Geology and Paleontology, and China MOST 973 programs.
The authors declare that they have no competing financial interests.
About this article
Cite this article
Kaufman, A., Xiao, S. High CO2 levels in the Proterozoic atmosphere estimated from analyses of individual microfossils. Nature 425, 279–282 (2003). https://doi.org/10.1038/nature01902
Journal of Earth Science (2022)
Scientific Reports (2019)
Environmental Earth Sciences (2018)
Nature Communications (2016)