Global imprint of a 70-yr oscillatory-like behavior in sea surface temperature: possible implications for the 'hiatus' in global warming

The increase of global mean surface temperature shows three stagnation periods since the 1860s, including the current ‘hiatus', which began in the late 1990s. Cooling over the eastern tropical Pacific, linked by previous studies to the observed remarkably strong trade wind intensification, has been noted also to contribute markedly to the observed reduced global warming rate in the last decade. However, the attribution of such behavior to a physical mechanism is still an unresolved issue.

In this study, a statistical approach is applied to decompose near-global sea surface temperature (SST) records, using Multi-Channel Singular-Spectrum analysis (MCSSA). Derived results suggest that not only anthropogenic and natural forcing agents, but also long-term internal climate variability, may have had a significant impact on the past temperature records, and therefore could also significantly influence global temperature behavior in the coming decades. A cooling component, we find over the central and eastern tropical Pacific, is part of a global pattern--with a ~70-yr time scale—that was apparently common to all three hiatus periods. The central and eastern tropical Pacific cooling leads the major global-mean cool phase of the mode (e.g., the global mean or northern hemisphere mean SST anomaly) by about ¼ cycle, or 16 years. Thus current cool conditions in the tropical Pacific could be a precursor to a continued global cooling contribution from the mode, which, in combination with anthropogenic warming, could lead to continued hiatus conditions for the next decade or two. North Atlantic SST anomalies (AMO-like signal) are coherent with the surface wind field and sea level pressure anomalies in the tropical Pacific, suggestive of coupled feedback processes in this region. In summary, while the physical origin(s) of the MCSSA-derived mode are still uncertain, if the phenomenon is predominantly due to natural internal variability, it could lead to a prolongation of the hiatus for the next few decades.