Impact of dust in PMIP-CMIP6 mid-Holocene simulations with the IPSL model

Abstract

Abstract. We investigate the climate impact of reduced dust during the mid-Holocene using\nsimulations with the IPSL model. We consider simulations where dust is\neither prescribed from an IPSL PI simulation or from CESM simulations\n(Albani et al., 2015). In\naddition, we also consider an extreme mid-Holocene case where dust is\nsuppressed. We focus on the estimation of the dust radiative effects and the relative responses of the African and Indian monsoon, showing how local dust forcing or orography affect atmospheric temperature profiles, humidity and precipitation. The simulated mid-Holocene climate is statistically different\nin many regions compared to previous mid-Holocene simulations with the IPSL\nmodels. However, it translates to only minor improvements compared to\npalaeoclimate reconstructions, and the effect of dust has little impact on\nmid-Holocene model skill over large regions. Our analyses confirm the\npeculiar role of dust radiative effect over bright surfaces such as African\ndeserts compared to other regions, brought about by the change of sign of\nthe dust radiative effect at the top of atmosphere for high surface albedo.\nWe also highlight a strong dependence of results on the dust pattern. In\nparticular, the relative dust forcing between West Africa and the Middle East\nimpacts the relative climate response between India and Africa and between\nAfrica, the western tropical Atlantic and the Atlantic meridional\ncirculation. It also affects the feedback on the Atlantic Ocean thermohaline\ncirculation. Dust patterns should thus be better constrained to fully\nunderstand the changes in the dust cycle and forcing during the mid-Holocene,\nwhich also informs on the potential changes in key dust feedbacks in the\nfuture.