Reply to comment by W. F. Ruddiman on ‘‘A note on the relationship between...

Schmidt, G. A., and D. Shindell (2005), Reply to comment by W. F. Ruddiman on ‘‘A note on the relationship between ice core methane concentrations and insolation’’, Geophys. Res. Lett., 32, L15704, doi:10.1029/2005GL022982.

Schmidt et al. [2004] pointed out that linear correlations between CH4 and insolation used by Ruddiman [2003] to project CH4 trends over the Holocene were not appropriate. We note that this principal point of our paper is not disputed by Ruddiman [2005b]. Instead, Ruddiman’s comment uses an analogy with the end of Stage 11 to support his hypothesis: an argument that is not made by Ruddiman [2003], although it is made by Ruddiman [2005a] and was briefly addressed by Schmidt et al. [2004]. This analogy depends on one principle issue: the association of uncertain timing of the end of Stage 11 in Vostok, EPICA Dome C and ocean sediment cores [McManus et al., 2003] to the (well-dated) changes in insolation (the implicit link between Figures 1a and 1b by Ruddiman [2005b]). We maintain that dating uncertainties preclude such a strong identification, while Ruddiman does not. We do not dispute the size of CH4 changes at glacial inception, only whether glacial inception was to be expected in the Holocene. Much of the response to Ruddiman’s comment is already clearly covered by Schmidt et al. [2004], but we nevertheless address his four points in turn.

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