The early anthropogenic hypothesis: Challenges and responses

Abstract

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.

Science with Society in the Anthropocene

“…Paul Crutzen proposes that the Anthropocene Age started with the industrial revolution, and that phenomena such as the ozone hole and climate change now demonstrate that the human species can be regarded as a geological factor modifying the earth system (Ruddiman 2003(Ruddiman , 2007. This notion of the Anthropocene indicates fundamental challenges to mankind in general and to sciences in particular, as the interaction between human and social systems have to be addressed on all scales (Steffen et al 2011).…”

The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean

“…Medieval climate was also characterized by hydrometeorological variability across North America (Cook et al, 2007) and Eurasia (Treydte et al, 2006). Solar and volcanic activity (Crowley, 2000;Ammann et al, 2007), solar-oceanic feedbacks (Bond et al, 2001), ocean circulation (Broecker, 2001), Pacific Ocean-atmospheric processes (Cook et al, 2007), and land-use changes Ruddiman, 2007) have all been proposed as factors influencing MCA-LIA climate.…”

Devils Hole, Nevada--A Primer

“…The most recent portion of the Devils Hole record suggests-as do SST records off California-that the warmest portion of the current interglaciation began by 17,000 years before present (Winograd and others, 2006). From these data one might infer that in the absence of any mitigating conditions, such as anthropogenically induced climate warming, the onset of a period of global cooling is imminent or even overdue on a geologic time scale (Ruddiman, 2007). However, some researchers have suggested that the current interglaciation might continue for tens of thousands of years (Berger and Loutre, 2002).…”