Tropical Ocean Temperatures Over the Past 3.5 Million Years

Abstract

Birth of the Cool: Over the past 4 million years or so, tropical sea surface temperatures have experienced a cooling trend (see the Perspective by Philander ). Herbert et al. (p. 1530 ) analyzed sea surface temperature records of the past 3.5 million years from low-latitude sites spanning the world's major ocean basins in order to determine the timing and magnitude of the cooling that has accompanied the intensification of Northern Hemisphere ice ages since the Pliocene. Martínez-Garcia et al. (p. 1550 ) found that the enigmatic eastern equatorial Pacific cold tongue, a feature one might not expect to find in such a warm region receiving so much sunlight, first appeared between 1.8 and 1.2 million years ago. Its appearance was probably in response to a general shrinking of the tropical warm water pool caused by general climate cooling driven by changes in Earth's orbit.