Sea Surface Temperatures in the Eastern Equatorial Pacific and Surface Temperatures in the Eastern Cordillera of Colombia During El Niño: Implications for Pliocene Conditions

Abstract Regressions of surface temperatures in the Eastern Cordillera of Colombia with sea surface temperatures (SSTs) in the equatorial Pacific, and specifically with Niño1+2 and Niño3 temperature anomalies, show that the Eastern Cordillera warms or cools by approximately half of the amplitude of the variation of SSTs in the eastern tropical Pacific. Because Pliocene SSTs in the eastern tropical Pacific resemble those during major El Niño events, when SSTs warm by ~4°C, these regressions suggest that the Pliocene Eastern Cordillera was warmer by ~2°C at both high and low elevations. Such post‐Pliocene cooling is smaller than the ~9–12°C inferred from fossil pollen assemblages, but comparable to recent estimates of Anderson et al. of 3 ± 1°C (1 σ ) since ~8 Ma. This change in surface temperature could be explained by a change in regional climate associated with a different tropical Pacific SST distribution and therefore would require neither an elevation change of the Eastern Cordillera since that time nor a change between Pliocene and present‐day temperatures in the tropics that is as large as estimates of the global change of ~2.5–4°C.