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A reply to the critical evaluation of the Oscillayers methods and dataset


Gamisch, Alexander (2020), A reply to the critical evaluation of the Oscillayers methods and dataset, Dryad, Dataset,


The authors offered a critical evaluation of theory and methods of the Oscillayers approach and attempted to test its utility by reproducing global circulation model (GCM-)based palaeo-climatic reconstructions of two variables (Bio1 and Bio12) for four different time points (130kyr, 787kyr, 3.2Myr, 3.3Myr). They concluded that Oscillayers show poor agreement with independent GCMs and thus do not provide a robust approximation of palaeoclimate throughout the Plio-Pleistocene. Here, I demonstrate that the authors underestimated the ability of Oscillayers to reproduce independent GCMs by not taking into account inter-framework differences between the models used to generate the Oscillayers and PaleoClim datasets. However, upon correcting this systematic error, differences in Bio1 and Bio12 between Oscillayers and PaleoClim GCMs are less than ± 1°C or ± 50 mm on average in 35.9% (range: 11.8 – 59.0%) or 46.7% (20.8 – 66.0%) of values, respectively. Thus the agreement between Oscillayers and PaleoClim is on average c. 1.5 to 2 times higher than estimated by the authors and mostly well above the inter-model agreement between two commonly used GCMs (CCSM, MIROC) for the Last Glacial Maximum (LGM). Consequently, I conclude that the Oscillayers approach does provide reasonably robust approximations of palaeo-climate throughout the Plio‐Pleistocene. Some clarifications are given.