Geographical distribution of surface temperature change over the 2003-2013 decade.

Abstract:

Global surface temperatures have increased less rapidly since the early 2000s than during the previous decades. This slowdown in global surface evolution (also called hiatus) has several possible causes, ranging from decreased net radiative forcing to internal rearrangement of heat inside the ocean between the surface and the deep ocean. Several studies have favored the latter explanation and have invoked different ocean basins as potential warming sinks. Here we investigate the regional distribution of the reported temperature slowdown during the 2003-2013 decade. We successively analyse land and ocean surface temperatures using different data sets. For the ocean, we use sea surface temperature data as well as ocean thermal expansion of the upper 100 m estimated with Argo measurements and ocean reanalyses. We find that during the study period (largely representative of the hiatus), land surface temperatures have increased at a rate not significantly lower than over the previous century. For the oceans, we estimated the surface temperature (and 0-100 m thermal expansion) in different latitudinal bands and different ocean basins and found that the most of the observed slowdown of the global mean surface temperature comes from the eastern tropical Pacific (20°S-20°N, 80°W-150°W). This region shows a significant cooling during the 2003-2013 decade, not seen elsewhere. Looking at seasonal variations, we also found that cooling dominantly occurs during the December-January-February season. Comparison of the eastern tropical Pacific sea surface temperature cooling with the global mean shows that the observed pause in the global mean surface temperature evolution of the recent years can be largely explained by this region. This result is well compatible with some recently proposed mechanisms of heat redistribution inside the ocean.