Abstract
Abstract. We carry out three sets of last interglacial (LIG) experiments, named lig127k, and of pre-industrial experiments, named piControl, both as part of PMIP4/CMIP6 using three versions of the MIROC model: MIROC4m, MIROC4m-LPJ, and MIROC-ES2L. The results are compared with reconstructions from climate proxy data. All models show summer warming over northern high-latitude land, reflecting the differences between the distributions of the LIG and present-day solar irradiance. Globally averaged temperature changes are −0.94 K (MIROC4m), −0.39 K (MIROC4m-LPJ), and −0.43 K (MIROC-ES2L). Only MIROC4m-LPJ, which includes dynamical vegetation feedback from the change in vegetation distribution, shows annual mean warming signals at northern high latitudes, as indicated by proxy data. In contrast, the latest Earth system model (ESM) of MIROC, MIROC-ES2L, which considers only a partial vegetation effect through the leaf area index, shows no change or even annual cooling over large parts of the Northern Hemisphere. Results from the series of experiments show that the inclusion of full vegetation feedback is necessary for the reproduction of the strong annual warming over land at northern high latitudes. The LIG experimental results show that the warming predicted by models is still underestimated, even with dynamical vegetation, compared to reconstructions from proxy data, suggesting that further investigation and improvement to the climate feedback mechanism are needed.
Highlights
The last interglacial (LIG, 130–116 ka) is referred to as the warmest period in the recent glacial–interglacial cycle (NGRIP members, 2004; Overpeck et al, 2006; Lang and Wolff, 2011)
A look at the globally averaged annual mean temperature changes in the present study shows that there is a slight cooling from PI for all three models: −0.94 K (MIROC4m), −0.39 K (MIROC4m-LPJ), and −0.43 K (MIROC-ES2L)
All models show the largest regional warming (> 6 K) in June–July–August (JJA) over northern high-latitude land and the largest global cooling in December–January–February (DJF), which corresponds to increased boreal summer solar irradiance and decreased boreal winter solar irradiance in the LIG, respectively
Summary
The last interglacial (LIG, 130–116 ka) is referred to as the warmest period in the recent glacial–interglacial cycle (NGRIP members, 2004; Overpeck et al, 2006; Lang and Wolff, 2011). Leaf area indices, MIROC-ES2L prescribes modern vegetation distribution but allows leaf area indices to respond to the simulated climate, and MIROC4m-LPJ simulates both vegetation distribution and leaf area indices in response to climate change. Comparisons of these three models provide an opportunity to loosely reveal the effect of no, partial, and full vegetation feedbacks. We apply the LIG boundary conditions provided by the PMIP4 to three different versions of atmosphere–ocean coupled general circulation models (AOGCMs), which belong to the Model for Interdisciplinary Research on Climate (MIROC) family, and compare results with the pre-industrial simulations, focusing on the different treatment of vegetation among the three models. The feedback mechanism for the Arctic warming amplification is discussed
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