The early anthropogenic hypothesis: Challenges and responses
Article first published online: 31 OCT 2007
Copyright 2007 by the American Geophysical Union.
Reviews of Geophysics
Volume 45, Issue 4, December 2007
How to Cite
2007), The early anthropogenic hypothesis: Challenges and responses, Rev. Geophys., 45, RG4001, doi:10.1029/2006RG000207.(
- Issue published online: 31 OCT 2007
- Article first published online: 31 OCT 2007
- Manuscript Accepted: 26 MAR 2007
- Manuscript Revised: 15 JAN 2007
- Manuscript Received: 22 JUN 2006
 Ruddiman (2003) proposed that late Holocene anthropogenic intervention caused CH4 and CO2 increases that kept climate from cooling and that preindustrial pandemics caused CO2 decreases and a small cooling. Every aspect of this early anthropogenic hypothesis has been challenged: the timescale, the issue of stage 11 as a better analog, the ability of human activities to account for the gas anomalies, and the impact of the pandemics. This review finds that the late Holocene gas trends are anomalous in all ice timescales; greenhouse gases decreased during the closest stage 11 insolation analog; disproportionate biomass burning and rice irrigation can explain the methane anomaly; and pandemics explain half of the CO2 decrease since 1000 years ago. Only ∼25% of the CO2 anomaly can, however, be explained by carbon from early deforestation. The remainder must have come from climate system feedbacks, including a Holocene ocean that remained anomalously warm because of anthropogenic intervention.