New paper finds climate models are unable to reproduce warming during the Holocene Climate Optimum

A new paper published in Climate of the Past finds that climate models are unable to reproduce the warming in East Asia during the Holocene Climate Optimum. According to the authors, "Much effort has been devoted to reconstructing the mid-Holocene climate over East Asia using a variety of proxy data, suggesting that China experienced warmer and wetter than present climate conditions as a whole during that time," however climate model "results are contrary to the warming reconstructed from multiple proxy data for the mid-Holocene." The paper adds to many other peer-reviewed publications demonstrating that climate models are unable to reproduce the Holocene Climate Optimum, Egyptian, Minoan, Roman, and Medieval Warming Periods, all of which were warmer than the present. Climate models are unable to reproduce the known climate of the past, much less the future. 

Clim. Past, 9, 2153-2171, 2013 www.clim-past.net/9/2153/2013/ doi:10.5194/cp-9-2153-2013 Mid-Holocene ocean and vegetation feedbacks over East Asia

Z. Tian^1,2 and D. Jiang^1,3,4
1Nansen–Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
²University of Chinese Academy of Sciences, Beijing, China
³Key Laboratory of Regional Climate–Environment Research for Temperate East Asia, Chinese Academy of Sciences, Beijing, China
⁴Climate Change Research Center, Chinese Academy of Sciences, Beijing, China
Abstract. Mid-Holocene ocean and vegetation feedbacks over East Asia are investigated by a set of numerical experiments performed with the version 4 of the Community Climate System Model (CCSM4). With reference to the pre-industrial period, most of the mid-Holocene annual and seasonal surface-air temperature and precipitation changes are found to result from a direct response of the atmosphere to insolation forcing, while dynamic ocean and vegetation modulate regional climate of East Asia to some extent. Because of its thermal inertia, the dynamic ocean induced an additional warming of 0.2 K for the annual mean, 0.5 K in winter (December–February), 0.0003 K in summer (June–August), and 1.0 K in autumn (September–November), but a cooling of 0.6 K in spring (March–May) averaged over China, and it counteracted (amplified) the direct effect of insolation forcing for the annual mean and in winter and autumn (spring) for that period. The dynamic vegetation had an area-average impact of no more than 0.4 K on the mid-Holocene annual and seasonal temperatures over China, with an average cooling of 0.2 K for the annual mean. On the other hand, ocean feedback induced a small increase of precipitation in winter (0.04 mm day⁻¹) and autumn (0.05 mm day⁻¹), but a reduction for the annual mean (0.14 mm day⁻¹) and in spring (0.29 mm day⁻¹) and summer (0.34 mm day⁻¹) over China, while it also suppressed the East Asian summer monsoon rainfall. The effect of dynamic vegetation on the mid-Holocene annual and seasonal precipitation was comparatively small, ranging from −0.03 mm day⁻¹ to 0.06 mm day⁻¹ averaged over China. In comparison, the CCSM4 simulated annual and winter cooling over China agrees with simulations within the Paleoclimate Modeling Intercomparison Project (PMIP), but the results are contrary to the warming reconstructed from multiple proxy data for the mid-Holocene. Ocean feedback narrows this model–data mismatch, whereas vegetation feedback plays an opposite role but with a level of uncertainty.