The international study, co-authored by Josh Willis of NASA's Jet Propulsion Laboratory, determined the energy currently stored in the ocean is enough to power nearly 500 100-watt light bulbs for each of the roughly 6.7 billion people on the planet.
"We are seeing the global ocean store more heat than it gives off," said John Lyman, an oceanographer at the National Oceanic and Atmospheric Administration's Joint Institute for Marine and Atmospheric Research. Lyman led the study that analyzed nine different estimates of heat content in the upper ocean from 1993 to 2008.
"The ocean is the biggest reservoir for heat in the climate system," Willis said. "So as the planet warms, we're finding that 80 to 90 percent of the increased heat ends up in the ocean."
The researchers explained a warming ocean is a direct cause of global sea level rise, since seawater expands and takes up more space as it heats. The researchers said that expansion accounts for about one-third to one-half of global sea level rise.
The team that included scientists from Britain's Headley Center for Climate Prediction and Research, the University of Hamburg in Germany and the Meteorological Research Institute in Japan reports its findings in the journal Nature.