Eos, Transactions American Geophysical Union

On “The Holocene CO2 rise: Anthropogenic or natural?”



Because the rising carbon dioxide (C02) trend in the late Holocene differs markedly from the natural C02 drops that occurred during the three previous interglaciations, I proposed that the Holocene increase is anthropogenic [Ruddiman, 2003]. Broecker and Stocker [2006] recently proposed using the stage 11 interglaciation (the fourth one before the present) as a potentially better analog for the Holocene because low orbital eccentricity produced similar insolation trends. They aligned termination V (the deglaciation that led into stage 11) with termination I (the most recent deglaciation) and counted forward in ‘elapsed time’ (Figure la).They noted that trends in C02 and deuterium (δD) remained at full interglacial levels early in both interglaciations and on that basis concluded that the late Holocene warmth is not only natural in origin but is also likely to last thousands of years into the future.