Collaborative Research: P2C2--Implications of the Early Anthropogenic Hypothesis

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This is a project to continuing testing aspects of the Early Anthropogenic Hypothesis, the conjecture that early agricultural practices by humans altered the terrestrial carbon cycle, causing a net increase in atmospheric CO2 and methane that offset a natural decline during the Holocene (the last 10,000 years). The hypothesis is based on observations of orbital climate variability. During previous interglacials atmospheric CO2 and methane began to decline early, leading to cooling and ultimately glacial inception. The Holocene is an outlier in this regard because the greenhouse gases increase in the atmosphere from the mid-Holocene to preindustrial values in the mid 1700s. There is great debate about why.Based on new information that per capita land use has changed, the project will test whether this can account for the rise in greenhouse gases observed during the Holocene. It will invoke a series of novel general circulation experiments for the last 6000 years, comparing the expected natural changes with those that might have been caused by anthropogenic impacts. The researchers will use the Coupled Environmental System Model (CESM1) and compare the results with observational data for the Holocene.Because it is controversial, the Early Anthropogenic Hypothesis has generated much research activity in the field of paleoclimatology, resulting in dedicated symposia, journal volumes, popular books and public lectures.