Global‐scale modes of surface temperature variability on interannual to century timescales

Abstract

Using 100 years of global temperature anomaly data, we have performed a singular value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio‐temporal “modes” of global climate variability. Statistical significance is determined from confidence limits obtained by Monte Carlo simulations. Secular variance is dominated by a globally coherent trend, with nearly all grid points warming in phase at varying amplitude. A smaller, but significant, share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude North Atlantic with a roughly centennial timescale. Spatial patterns associated with significant peaks in variance within a broad period range from 2.8 to 5.7 years exhibit characteristic El Niño‐Southern Oscillation (ENSO) patterns. A recent transition to a regime of higher ENSO frequency is suggested by our analysis. An interdecadal mode in the 15‐to‐18 years period range appears to represent long‐term ENSO variability. This mode has a sizeable projection onto global‐average temperature, and accounts for much of the anomalous global warmth of the 1980s. A quasi‐biennial mode centered near 2.2‐years period and a mode centered at 7‐to‐8 years period both exhibit predominantly a North Atlantic Oscillation (NAO) temperature pattern. A potentially significant “decadal” mode centered on 11‐to‐12 years period also exhibits an NAO temperature pattern and may be modulated by the century‐scale North Atlantic variability.