Graph showing monthly changes in ocean heat content for the entire water column (seabed to surface) from 1992 to 2019 in zettajoules. One zettajoulse is equal to 1,000,000,000,000,000,000,000 joules. The oceans have a very high heat capacity and have absorbed 90% of the warming that has occurred in the atmosphere in recent decades. As water warms it expands leading to higher sea levels, which increase flood risks and displace populations. Warmer oceans also bleach corals, increase sea ice loss and intensify hurricanes and typhoons.