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Palaeoclimate

Atmospheric carbon footprints?

Nature Geoscience volume 2, pages 170–172 (2009)Cite this article

According to one controversial idea, increases in atmospheric greenhouse-gas concentrations due to human activities can be detected as early as several thousand years ago. Eight years after the publication of this hypothesis, controversy continues.

The large increase in greenhouse gases since AD 1750 (ref. 1) is an unequivocal marker of humanity's influence on the planet. Climate scientists tend to draw a sharp division between this recent industrial period and earlier times wherein greenhouse-gas variations are attributed to natural causes. However, this view is not universal: Bill Ruddiman champions an 'early anthropogenic hypothesis' instead, stating that humans already had a significant effect on the Earth's climate many thousands of years ago, through carbon emissions mainly associated with rice farming, animal husbandry, biomass burning and deforestation2,3. Although elements of this idea have been discussed before4, Ruddiman's initial paper on the topic2 made the hypothesis popular and generated a lively scientific debate. An American Geophysical Union (AGU) session 'Origin of Late Holocene (Pre-Industrial) Increases in Atmospheric CO2 and CH4' at the Fall Meeting in December 2008 in San Francisco5 was devoted to discussing this hypothesis in light of the current understanding of natural climate and greenhouse-gas cycles.

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Figure 1: Debated human footprint5.

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  1. Edward J. Brook is at the Department of Geosciences, Oregon State University, Corvallis, Oregon 97330, USA. brooke@geo.oregonstate.edu,

    Edward J. Brook

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  1. Edward J. Brook
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Brook, E. Atmospheric carbon footprints?. Nature Geosci 2, 170–172 (2009). https://doi.org/10.1038/ngeo446

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