Global mean sea level (GMSL)—the height of the oceans averaged over the globe (or over a large portion of the globe) is a crucial barometer of climate change because it reflects both the amount of heat being added to the oceans and the mass loss of global ice reservoirs (Greenland, Antarctica, glaciers, etc.). As such, it is important to precisely measure changes in GMSL and determine what is causing these changes. GMSL can also be used as a metric for assessing the impacts of sea level rise on coastal infrastructure and populations, and so knowledge of changes in GMSL is important for communicating climate change impacts to policymakers, stakeholders, and the public.