Evaluation of PMIP2 and PMIP3 simulations of mid-Holocene climate in the Indo-Pacific, Australasian and Southern Ocean regions

Abstract

Abstract. This study uses the "simplified patterns of temperature and effective precipitation" approach from the Australian component of the international palaeoclimate synthesis effort (INTegration of Ice core, MArine and TErrestrial records -OZ-INTIMATE) to compare atmosphere-ocean general circulation model (AOGCM) simulations and proxy reconstructions. The approach is used in order to identify important properties (e.g. circulation and precipitation) of past climatic states from the models and proxies, which is a primary objective of the Southern Hemisphere Assessment of PalaeoEnvironment (SHAPE) initiative. The AOGCM data are taken from the Paleoclimate Modelling Intercomparison Project (PMIP) mid-Holocene (ca. 6000 years before present, 6 ka) and pre-industrial control (ca. 1750 CE, 0 ka) experiments. The synthesis presented here shows that the models and proxies agree on the differences in climate state for 6 ka relative to 0 ka, when they are insolation driven. The largest uncertainty between the models and the proxies occurs over the Indo-Pacific Warm Pool (IPWP). The analysis shows that the lower temperatures in the Pacific at around 6 ka in the models may be the result of an enhancement of an existing systematic error. It is therefore difficult to decipher which one of the proxies and/or the models is correct. This study also shows that a reduction in the Equator-to-pole temperature difference in the Southern Hemisphere causes the midlatitude westerly wind strength to reduce in the models; however, the simulated rainfall actually increases over the southern temperate zone of Australia as a result of higher convective precipitation. Such a mechanism (increased convection) may be useful for resolving disparities between different regional proxy records and model simulations. Finally, after assessing the available datasets (model and proxy), opporPublished by Copernicus Publications on behalf of the European Geosciences Union.

Human Influence on the Climate System

“…CMIP6 models tend to underestimate the cooling over land, but agree better with oceanic reconstructions. For the mid-Holocene, the regional biases found in CMIP5 simulations are similar to those in pre-industrial and historical simulations (Harrison et al, 2015;Ackerley et al, 2017), suggesting common causes. CMIP5 models underestimate Arctic warming in the mid-Holocene (Yoshimori and Suzuki, 2019).…”

Late Quaternary Climate Variability and Change from Aotearoa New Zealand Speleothems: Progress in Age Modelling, Oxygen Isotope Master Record Construction and Proxy-Model Comparisons

“…Spatially heterogeneous atmospheric circulation features across the Southern Hemisphere for the mid-Holocene, as seen climate model simulations, indicate reduced zonal flow across South American and Australian sectors of the high-middle and polar latitudes [68,132]. As a consequence, extratropical westerlies may have been weaker during the mid-Holocene over certain parts of the southern hemisphere, for certain seasons, despite a more intense overall upper tropospheric southern jet stream at times [68].…”