Abstract
Abstract. The pre-industrial millennium is among the periods selected by the Paleoclimate Model Intercomparison Project (PMIP) for experiments contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and the fourth phase of the PMIP (PMIP4). The past1000 transient simulations serve to investigate the response to (mainly) natural forcing under background conditions not too different from today, and to discriminate between forced and internally generated variability on interannual to centennial timescales. This paper describes the motivation and the experimental set-ups for the PMIP4-CMIP6 past1000 simulations, and discusses the forcing agents orbital, solar, volcanic, and land use/land cover changes, and variations in greenhouse gas concentrations. The past1000 simulations covering the pre-industrial millennium from 850 Common Era (CE) to 1849 CE have to be complemented by historical simulations (1850 to 2014 CE) following the CMIP6 protocol. The external forcings for the past1000 experiments have been adapted to provide a seamless transition across these time periods. Protocols for the past1000 simulations have been divided into three tiers. A default forcing data set has been defined for the Tier 1 (the CMIP6 past1000) experiment. However, the PMIP community has maintained the flexibility to conduct coordinated sensitivity experiments to explore uncertainty in forcing reconstructions as well as parameter uncertainty in dedicated Tier 2 simulations. Additional experiments (Tier 3) are defined to foster collaborative model experiments focusing on the early instrumental period and to extend the temporal range and the scope of the simulations. This paper outlines current and future research foci and common analyses for collaborative work between the PMIP and the observational communities (reconstructions, instrumental data).
Highlights
Based on a vast collection of proxy and observational data sets, the Common Era (CE; approximately the last 2000 years) is the best-documented interval of decadalto centennial-scale climate change in Earth’s history (PAGES2K Consortium, 2013; Masson-Delmotte et al, 2013)
Paleoclimate Model Intercomparison Project (PMIP) discriminates between the experiments that are endorsed by the World Climate Research Program (WCRP) CMIP6 committee (PMIP4 Tier 1: past1000, Mid Holocene and Last Interglacial, Last Glacial Maximum, and Mid Pliocene Warm Period; see Kageyama et al, 2016) and additional simulations (PMIP4 Tier 2 and Tier 3) that are more tailored to specific interests of the palaeoclimate modelling community
The PMIP4-CMIP6 past1000 simulations provide a framework for integrated studies of climate evolution during the pre-industrial period
Summary
Based on a vast collection of proxy and observational data sets, the Common Era (CE; approximately the last 2000 years) is the best-documented interval of decadalto centennial-scale climate change in Earth’s history (PAGES2K Consortium, 2013; Masson-Delmotte et al, 2013). González-Rouco et al, 2003; Raible et al, 2014; Ortega et al, 2015; Zanchettin et al, 2015; Landrum et al, 2013), and regional processes in greater detail (Goosse et al, 2006, 2012; PAGES2k-PMIP3 Group, 2015; Coats et al, 2015; Luterbacher et al, 2016) They have allowed individual groups to study specific components of the climate system, such as the carbon cycle (Jungclaus et al, 2010; Lehner et al, 2015; Chikamoto et al, 2016), or aerosols and short-lived gases The CMIP6 protocols ensure a better interaction between related MIPs. For example, the PMIP4 past1000 experiment is closely related to the more process-oriented suite of simulations in the Model Intercomparison Project on the climatic response to volcanic forcing (VolMIP, Zanchettin et al, 2016).
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