| Ocean heat content is compared among nine analyses of global ocean temperature during 1960--2002. Two are independent of numerical modeling, and the rest rely on data assimilation, which utilizes an ocean general circulation model and observations to create an analysis. Most analyses show gradual warming of the global ocean with an ensemble trend of 0.77 x 108 J m-2 (10 yr)-1 (=0.24 W m-2) as the result of rapid warming in the early 1970s and again beginning around 1990. Three explanations for this decadal variability are proposed and tested: the effect of three major volcanic eruptions, the uncorrelated contribution of heat content variations in individual ocean basins, and the effect of time-dependent bias in the set of historical observations. It was found that the second hypothesis contributed significantly to heat content variability. |
