Global Patterns of Increasing Interannual Variability of Surface Air Temperature throughout the Holocene

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Abstract We examine the interannual variability of surface air temperature throughout the Holocene and the associated mechanisms by using our new set of Holocene transient simulations spanning from 11.5 ka before present to the preindustrial period. The interannual variability of annual, winter, and summer temperature increases with a linear trend of 0.005°, 0.007°, and 0.005°C ka −1 globally since 11.5 ka, respectively. The temperature variability evolution can be explained by the orbital forcing in most regions, with an additional impact from the retreat of ice sheets over North America and Europe but, overall, little effect from the change in atmospheric greenhouse gas concentrations. In response to the insolation change from the early to late Holocene, primarily due to the precession, variations in energy balance components contribute to the enhanced temperature variability by a global mean of 8%–10%. Specifically, surface net heat flux and radiation flux at the top of atmosphere generally play dominant roles, while atmospheric energy convergence minus storage partially offsets them at the global scale. Regionally, cloud effects and sea surface temperature variability are important in low latitudes, while sea ice changes are the main factors in mid- to high-latitude oceans. Due to the seasonal contrast in insolation, various responses of global surface mean temperature and its meridional gradient, sea ice fraction, total cloud, and surface soil moisture result in the seasonal difference in temperature variability change, particularly in the Arctic Ocean and northern continents. The simulated temperature variability change throughout the Holocene is qualitatively consistent with most of the available proxy data, although uncertainties still exist on both sides. Significance Statement The purpose of this article is to investigate the year-to-year variability of surface air temperature throughout the Holocene from a global perspective. This is important because enhanced temperature variability increases the risk of cold and warm extremes, causing more profound socioeconomic impacts than the mean state. Based on our new set of Holocene transient simulations spanning from 11.5 ka before present to 1850, the results display a globally increasing variability of annual and seasonal temperatures since 11.5 ka primarily due to the orbital forcing. Associated mechanisms, including cloud effects, sea surface temperature variability, and sea ice changes, are highlighted from an energy balance decomposition. This study deepens our understanding of the evolution and mechanism of global temperature variability under warming backgrounds.

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