Summer amplification of interannual variability changes in surface air temperature during the last interglacial period

Temperature variability refers to temperature fluctuations around the mean state, which closely connects with the probability of extreme events. Examining temperature variability during past warm periods in Earth's history is essential for elucidating its future trends. We quantitatively analyze the interannual variability changes in near-surface air temperature and associated mechanisms during the last interglacial period (LIG, ∼127 ka) using the Paleoclimate Modeling Intercomparison Project Phase 4 (PMIP4) models. Relative to the preindustrial period, the LIG interannual variability of temperature increases slightly at the global scale. Summertime variability varies more dramatically at the regional scale, especially in high latitudes, East Asia, and North Africa, where it increases by more than 15 % in comparison to small changes for the winter and annual mean. In high-latitude oceans, radiation fluxes notably contribute to temperature variability change due to sea ice melting. Cloudiness changes dominate enhanced summer temperature variability in East Asia and both tropical land and oceans, while net surface heat flux and atmospheric energy convergence minus storage (CONV) influence other land regions. Additionally, CONV plays a larger role in the mid-to-high latitudes during winter than during summer. In low-latitude oceans, the distribution of temperature variability change is shaped by the mutual compensation between net surface heat flux and CONV. Simulated temperature variability changes generally agree with proxy data, although discrepancies exist in North Asia, East Asia, North Africa, North America, and South America.