Temporal and spatial response of Holocene temperature to solar activity

Based on the latest database, we analyze the characteristics of the changing trends of sunspot number (SSN) and temperatures of the global mean surface (GMST) as well as six latitude bands during the Holocene, aiming to explore the long-term responses of the Holocene temperatures to solar activity. We adopt two methods, i.e., the 300-year moving average and the singular spectrum analysis to obtain the long-term trends of signals. We find that the average changes in the amplitude of temperatures in the Northern Hemisphere (NH) (3.65 °C) was greater than that in the Southern Hemisphere (SH) (1.28 °C) during the entire Holocene. There was one peak of temperatures (at 6500 BP) and two peaks of solar activity (at 4500 BP and 2000 BP) during our study interval. Spatially, the temperatures in the NH were more sensitive to solar forcing than those in the SH, especially in the latitude bands of 0°–30°N and 60°N-90°N. Moreover, the latitude band 0°-30°N had the strongest correlation with solar activity (C.C. = 0.38 for the 300-year moving average and C.C. = 0.55 for the singular spectrum analysis, p < 0.01), while the latitude band 60°S-90°S had the weakest correlation with solar activity (not significant in the statistical sense). Regarding the time response, solar forcing nearly did not affect the terrestrial temperatures in the early Holocene (8700 BP-6500 BP). While positive correlations started to be strong since 4500 BP and became stronger during 2000 BP-100 BP. All in all, the terrestrial temperatures were consistent with solar activity in the long-term trend during the Holocene, especially in the NH. Although many mysteries in historical climate reconstructions remain un-resolved, evaluating the impact of solar force on terrestrial temperature is crucial to reconstruct and predict terrestrial climate. Much deeper specific research on solar-terrestrial mechanisms deserves to be put on the agenda.