An isotopic (δ18O) enrichment trend from 1887 to 1998 recorded in the Malan ice core from the northern Tibetan Plateau indicates that temperatures there have warmed in the past century. Statistical analyses suggest that the annual δ18O in this ice core largely reflects air temperature variations in the warm season. Statistically significant modest to weak correlations were found between the annual δ18O and the North Atlantic Oscillation (NAO) index from May through October and the Southern Oscillation (SO) index from August through November, respectively. A multivariate linear regression shows that when combined, the NAO and SO account for 55% of the total variance in δ18O over the past century. Moreover, the correlations between δ18O and the NAO and the SO vary over the study period, as might be expected due to changes in the strength and amplitude of the NAO and SO over the past century.