The expansion of oceans as the climate warms has contributed to a rise in global sea levels of about 1.38 millimetres per year — roughly twice that of previous estimates.

Roelof Rietbroek at the University of Bonn in Germany and his colleagues analysed sea-surface heights from satellite radar data, and looked at changes in water storage from the Gravity Recovery And Climate Experiment (GRACE). They found that between 2002 and 2014, sea levels have increased in total by roughly 2.74 mm per year, with 1.38 mm of that coming from ocean thermal expansion and 1.08 mm from melting ice sheets, glaciers and other water sources on land, such as rivers.

The team also uncovered large regional differences. For example, the Philippines experienced a sea-level rise of about 14.7 mm per year, mostly because of thermal expansion of the ocean, whereas the central and eastern Pacific saw decreases.

Proc. Natl Acad. Sci. USA (2016)