PMIP-CMIP6 Experimental Design Discussion: Mid-Holocene

Please submit your comments in the Discussion section at the end of this page

The mid-Holocene (~6000 years ago) is often described as a warm state, or the most recent “climate optimum”, in which dominant features of the global hydrological cycle, such as the North African and Asian monsoon, were amplified. As such, the mid-Holocene has been the focus for paleo-data syntheses since the beginning of the PMIP project and therefore are well documented in terms of temperature, hydrological cycle and land surface type. Some long standing model-data disagreement are echoing preoccupations for future climate change, such as the systematic underestimation of the northward penetration of the African monsoon rainfall onto the continent compared to available records for the Mid-Holocene.

The reference experiment to which the mid-Holocene is compared to is the pre-industrial control, which is part of the DECK.

For the mid-Holocene, our proposed experimental set-up for PMIP-CMIP6 is unchanged compared to the PMIP3-CMIP5 set-up:

The main forcing is the insolation, and the astronomical parameters must be set to: eccentricity = 0.018682 obliquity = 24.105° perihelion-180° = 0.87°

Concentration of atmospheric trace gases: CO2 = 280 ppm CH4 = 650 ppb N2O = 270 ppb CFC = 0 O3 = same as in CMIP5 PI

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