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Abstract

Ocean heat content (OHC) provides a measure of ocean warming and is central to the global energy cycle and the other major Earth system cycles. This presentation introduces a community effort to synthesize estimates of past and future OHC changes and understanding of ocean warming trends, from global to regional scales, using observations and models. Since the 1950s, the ocean has become significantly warmer in the top 2000m, and warming rates are increasing. Oceans surged to another record-high temperature in 2022. Ocean warming is somewhat unevenly distributed although present in all ocean basins, revealing different regional driving mechanisms. Constrained projections suggest that current ocean warming is irreversible this century and will persist beyond 2100. By 2100, the global total 0-2000m ocean warming will likely be 2 to 6 times the observed 1958–2019 change, depending on emissions, with inter-basin differences. Ocean warming has extensive impacts and consequences which pose risks to marine ecosystems and human society. Research priorities will be highlighted.