Fine-grained paleoclimate surfaces as a key input to understanding and projecting patterns of biodiversity persistence under climate change

Chris Ware (1), Tom Harwood (1), James Gilmore (1), Simon Ferrier (1)

1 Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land & Water, GPO Box 1700, Canberra, ACT 2601, Australia *

Paleoclimatic stability has been shown to be fundamental in explaining patterns of biological persistence. Improving our understanding of paleoclimate-persistence relationships is critical to developing more robust projections of climate-change impacts on biodiversity. Previous descriptions of global paleoclimates fall into two categories: the use of coarse-grained global circulation model (GCM) climate surfaces, and statistically downscaled GCM surfaces based on current fine-grained climatologies. The former omit, by necessity, fine-grained detail which may be vital to explaining patterns of biological persistence, while the latter approach relies on several questionable assumptions (e.g. treating distance-to-coast effects as stationary, despite shifting coastlines). We have developed a new downscaling method which adjusts coarse-grained GCM surfaces to fine-grained surfaces (e.g. 1km resolution) based on physical relationships between radiation, climate, and surface terrain. Our method ensures internal consistency with GCM output by avoiding common assumptions in downscaling methods. The approach can be applied to past land extents presently under ocean, is amenable to independent evaluation, and is applicable to any past time for which GCM outputs and topographical data are available. These fine-grained paleoclimate surfaces open up considerable potential to develop novel approaches to analysing processes shaping biodiversity persistence under climate change. For example, we are currently using the surfaces to develop measures of cross-taxa habitat connectivity across space and time. Such approaches should improve our understanding of how paleoclimate dynamics have enabled the persistence of biological diversity, providing a stronger theoretical basis from which to project patterns of biological persistence into the future.

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