A climate change signal in the tropical Pacific emerges from decadal variability
Feng Jiang, Richard Seager, Mark A. Cane
Abstract
The eastern tropical Pacific has defied the global warming trend. There has been a debate about whether this observed trend is forced or natural (i.e., the Interdecadal Pacific Oscillation; IPO) and this study shows that there are two patterns, one that oscillates along with the IPO, and one that is emerging since the mid-1950s, herein called the Pacific Climate Change (PCC) pattern. Here we show these have distinctive and distinguishable atmosphere-ocean signatures. While the IPO features a meridionally broad wedge-shaped SST pattern, the PCC pattern is marked by a narrow equatorial cooling band. These different SST patterns are related to distinct wind-driven ocean dynamical processes. We further show that the recent trends during the satellite era are a combination of IPO and PCC. Our findings set a path to distinguish climate change signals from internal variability through the underlying dynamics of each. This study identifies a Pacific Climate Change Pattern, hypothesized to be radiatively-forced, that has been emerging in the tropical Pacific Ocean since the mid-1950s and is distinct from the naturally varying Interdecadal Pacific Oscillation.