|Figure: Typical scale gap between a coarse ESM and the actual topography that induces regional climates leaving a footprint in the proxy record. The RCM is able to explicitly resolve such processes, therefore bridging the scale gap.|
The understanding of past climates and prediction of future climate change relies on climate models that include the relevant physical processes of the climate system. The comparison of results from long term paleoclimate simulations with General Circulation Models (GCM) or Earth System Models (ESM) and paleoclimate reconstructions based on proxy data (e.g. ice cores, tree rings, sediments) gains understanding of the climate system dynamics and variability during the last 100.000 years (e.g. the BMBF founded PalMod Project, http://www.palmod.de) and assess possible future climate trajectories beyond this century during the next millennia.
However, the comparison between GCM/ESM and proxy data is burdened by the fact that most climate reconstructions are based on local or regional proxy data, whereas the paleoclimate GCM/ESM simulations have a rather coarse spatial resolution. This can lead to large biases over extensive regions and inhibits a realistic representation of the small-scale features or climate extremes that affect the proxy records.
To overcome this scale gap, different techniques are applied, ranging from a ‘naive’ approach based on selecting the closest grid point of the climate model to complex approaches that refine the simulated large-scale fields with the help of statistical or dynamical methods, i.e. by applying Regional Climate Models (RCM). To evaluate existing and developing new downscaling strategies, the PALEOLINK project (http://pastglobalchanges.org/ini/wg/2k-network/projects/paleolink/intro) has been initiated in cooperation with Patrick Ludwig from the Institute of Meteorology and Climate Research. PALEOLINK is imbedded in the PAGES (Past Global Changes) project (http://pastglobalchanges.org), which is an international effort to coordinate and promote past global change research. The PALEOLINK kickoff-meeting took place in April during the EGU 2018 in Vienna. A recent dynamical downscaling study for glacial conditions already indicates the benefit of the application of RCM in the paleoclimate context (Ludwig et at. 2017, DOI: 10.1002/2017GL073622).
Reference: Ludwig P, Gómez-Navarro JJ, Pinto JG, Raible CC, Wagner S, Zorita E (2018) Perspectives of Regional Paleoclimate Modelling. Ann NY Acad Sci doi:10.1111/nyas.13865
[Working group: Regional Climate and Weather Hazards]