Ocean temperatures chronicle the ongoing warming of Earth

To the Editor — e global ocean has absorbed 93% of the extra heat trapped by the Earth since 19701 and the rate of change in ocean heat content is a good estimate of the radiation imbalance at the top of the atmosphere2. Previously we reported3 a robust warming rate over the Earth’s area of 0.5–0.7 W m–2 during 2006–2014 using the global ocean data from the Argo array and three contrasting mapping methods: an optimal interpolation (OI), reduced space optimal interpolation (RSOI) and robust parametric t (RPF). We have extended these analyses over the additional 23 months of data from Argo to probe ocean heat content evolution through to November 2015.