Researchers launched more than 3,600 robotic profiling floats into the planet’s oceans that provide crucial information on upper layers of currents. Alicia Navidad/CSIRO

Just how much heat has been added to the world's oceans has been greatly underestimated, two studies published Sunday in the journal Nature Climate Change indicate. The planet’s oceans are like a sink for excess heat that has accumulated in Earth’s atmosphere over the last 100 years.

Oceans in the Southern Hemisphere have warmed twice as quickly after 1970 as scientists previously thought, according to the studies. The discrepancy, researchers say, comes from poor sampling data in the last decade and limitations in the technology that provides such data.

Beginning in 2004, researchers have deployed some 3,600 robotic devices called Argo floats into the world’s oceans to gather more accurate heat measurements. The floats measure temperatures in the upper layers of currents and provide data that is “really critical” to understanding global warming, Paul Durack, a researcher from the Lawrence Livermore National Laboratory, which led the study, told Scientific American. “The estimates that we had up until now have been pretty systematically underestimating the likely changes,” he said.

Researchers compared the data to sea-level rise and ocean warming in the Northern Hemisphere. The results suggest that scientists have misjudged global ocean warming by a huge factor of 24 to 58 percent. This is the first time scientists “have tried to estimate how much heat we’ve missed,” Durack said in a statement.

Over the past century, ocean temperatures have risen by an average of 0.18 degree Fahrenheit, or 0.1 degree Celsius. The warming has occurred up to a depth of 2,300 feet, or 700 meters, according to National Geographic. Higher ocean temperatures are associated with stronger and more frequent tropical storms and the spread of invasive species and marine diseases.

The new findings are important because the Southern Hemisphere accounts for about 60 percent of the world’s oceans. Oceans absorb roughly 90 percent of the planet’s excess heat, according to Discovery.