Earth's deep ocean must be shivering, because this dark abyss hasn't warmed since 2005, according to new NASA research.
These cold waters are leaving scientists puzzled as to why global warming appears to have slowed in recent years.
Scientists at NASA's Jet Propulsion Laboratory (JPL) analyzed satellite and direct ocean temperature data from 2005 to 2013 and found the ocean abyss 1.24 miles (1,995 meters) below the sea's surface hasn't experienced any measureable warming.
"The combination of satellite and direct temperature data gives us a glimpse of how much sea level rise is due to deep warming. The answer is - not much," JPL's William Llovel, lead author of the study, said in a statement.
Greenhouse gases are still abundant in the Earth's atmosphere, but global average surface air temperatures have stopped rising in tandem with the gases. The temperature of the top half of the world's ocean - above the 1.24-mile mark - is still climbing, as was demonstrated in a related study on the Southern Hemisphere's oceans, but not fast enough to account for the stalled air temperatures.
Some scientists believe this "missing heat" is being absorbed by Earth's deep oceans, but this new study is the first to test the theory, given that these parts are difficult to measure.
JPL scientists based their findings on combined data from NASA's Jason-1 and Jason-2 satellites, the agency's Gravity Recovery and Climate Experiment (GRACE) satellites, and a network of 3,000 floating temperature probes called Argo. They quite simply just subtracted the amount of sea level rise from the expansion in the upper ocean, and the amount of rise that came from added meltwater.
What remained - the amount of sea level rise caused by warming in the deep ocean - was essentially zero.
Though, that's not to say that climate change isn't still a current problem.
"The sea level is still rising," added study co-author Josh Willis. "We're just trying to understand the nitty-gritty details."
The findings were published in the journal Nature Climate Change.