New climate model and satellite data suggests that ocean warming from 1970 to 2004 in the upper levels of Southern Hemisphere oceans has been massively underestimated. The findings are reported in two new studies in the journal Nature Climate Change.
"This underestimation is a result of poor sampling prior to the last decade and limitations of the analysis methods that conservatively estimated temperature changes in data-sparse regions," said oceanographer Paul Durack, from Lawrence Livermore National Laboratory, and the lead author of one of the papers.
The findings are important because oceans absorb about 90 percent of the planet's excess heat, and the Southern Hemisphere accounts for 60 percent of the world's oceans. The latest data suggests that the planet is warming faster than previously thought.
"By using satellite data, along with a large suite of climate model simulations, our results suggest that global ocean warming has been underestimated by 24 to 58 percent," Durack said in a press release. "The conclusion that warming has been underestimated agrees with previous studies, however it's the first time that scientists have tried to estimate how much heat we've missed."
In 2004, researchers began collecting more accurate measurements by deploying 3,600 robotic measuring devices, called Argo floats, which relayed information on the heat stored in the upper layers of the world's ocean currents.
Determining how fast the oceans are warming relates directly to how fast the atmosphere is warming and how much sea levels will rise, the researchers wrote.
"Our other new study on deep-ocean warming found that from 2005 to the present, Argo measurements recorded a continuing warming of the upper-ocean," said co-author Felix Landerer of NASA's Jet Propulsion Laboratory, who contributed to both studies. "Using the latest available observations, we're able to show that this upper-ocean warming and satellite measurements are consistent."