Comparison of climate responses to orbital forcing at different latitudes during the Holocene

Abstract

Climate variability during the Holocene has become a widespread concern, and recent studies have compared the annual mean climate variability of the orbital forcing in the Holocene. Little is known about the response of the JJA (June to August) and DJF (December to February) mean surface temperature and precipitation to orbital forcing at different latitudes. In this study, using the outputs of the climatic sensitivity experiments of orbital forcing in models (NNU and TraCE), we compared the linear trends and spatial patterns of JJA and DJF mean surface temperature and precipitation at different latitudes. In addition, we compared the results of the models with the proxy data. The results of the models suggest that the decreased linear trends of JJA mean surface temperature occur in the middle and high latitudes of the Northern Hemisphere (NH-MHL) and tropics, but in the middle and high latitudes of the Southern Hemisphere (SH-MHL), which show increasing trends. The increased linear trends of the DJF mean surface temperature appeared in the NH-MHL, tropics, and SH-MHL. Moreover, the annual mean surface temperature shows increasing trends in the tropics and SH-MHL, and the decreasing trends of annual mean surface temperature arise in the NH-MHL. As for the results of precipitation, the linear trends of JJA and DJF mean precipitation in the low latitudes of the Northern Hemisphere (NH-LL) show decreasing trends. In the low latitudes of the Southern Hemisphere (SH-LL), the JJA mean precipitation shows increasing trends, whereas the DJF results increase first then decrease. By comparing the temperature proxies, we found that simulation results appear in agreement with most temperature proxies, however, they do not match few temperature reconstructions. Furthermore, the trends of JJA and annual mean temperature in the tropics cannot reproduce the reconstructed temperature. We note that the results of NNU are more similar to the temperature reconstructions than those of the TraCE. In summary, we analysed the linear trends of JJA and DJF mean surface temperature and precipitation at different latitudes, and compared the results of models with temperature reconstructions. Our results provide a reference for paleoclimatic research.