The world's oceans have absorbed more than 90 percent of the excess heat trapped by greenhouse gas emissions, and new ocean heat content measurements show that warming rates in both the deep ocean and surface layers are exceeding projections from climate models used in the most recent IPCC assessment report. The acceleration suggests that climate sensitivity, the amount of warming produced by a given increase in atmospheric CO2, may be at the higher end of the uncertainty range that climate models have estimated.
The consequences of accelerating ocean warming are already apparent. Global coral bleaching events are becoming more frequent and severe, with the current bleaching episode affecting the largest geographic extent of coral reef area ever recorded. Ocean warming is also intensifying tropical cyclone maximum wind speeds and expanding the geographic range of hurricane-force storms into latitudes that historically experienced only tropical storms, creating new risk profiles for coastal populations that have not historically prepared for such events.
