Decadal-scale variability of warm season temperature in Beijing over the past 2650 years

A continuous record of surface temperature for the past 2650 years was obtained in an earlier study from a Beijing stalagmite based on sedimentary layer counting and thickness measurements. Singular spectrum analysis, multi-taper and wavelet spectral analyses are used in this study to identify decadal-scale signals and their origins in this record. Besides long-term cycles of solar origin identified in earlier studies, this record contains cycles that dominate temperature with periods of 102-70, 66-50, 31, 25-22, 19, 15, 12 and 9 years. The 102-70, 25-22, 12 and 9 year cycles are attributable to solar variation, while the others are likely to be related to low-latitude ocean forcing. These results suggest that century-scale changes in the Beijing summer temperature over the past 2650 years are primarily controlled by solar variation, while ocean-atmospheric interactions play a prominent role in modulating decadal-scale variability.