Geology News Items
Dr. William Ruddiman to give talk at Baylor.Feb. 2, 2010
Early Agriculture Started the Anthropogenic Era Thousands of Years Ago.
Late in 2003, I posed the hypothesis indicated by the title of this talk by claiming that very early farming caused initially small releases of CO2 (by deforestation) and methane (by rice farming and livestock) that grew to be surprisingly large before 1850, the time when industrial-era emissions caused an explosive increase in greenhouse-gas concentrations. One of the claims of the hypothesis was that the warming effect from these agricultural emissions of CO2 and methane offset most of a natural cooling driven by Earth-orbital variations that would by now have caused the start of the next(natural) glaciation. Six years later, the hypothesis has generated a vigorous and still-growing debate in several scientific fields, including the interpretation of greenhouse-gas trends during previous interglaciations in ice cores, interpretations of pre-industrial versus industrial-era land clearance from land-use models, and the spread of agriculture across Eurasia, Africa, and the Americas during the last 7000 years. This lecture will summarize the evidence for the hypothesis, as well as the basis for some of the criticisms against it.