New research indicates that a current "pause" in global warming could be caused by the Atlantic Ocean, which is pulling heat from the atmosphere and taking it to its depths.
The break in global warming has recently stumped many scientists. Although the early 20th century saw rapid warming, the 21st century has seen relatively stable average temperatures on the Earth's surface.
Scientists have many theories about this period, including blaming it on air pollution, sunspots and even volcanoes. However, this new research suggests that some heat from the surface is now missing because it is going deep into the waters of the Atlantic Ocean and that this is all part of a natural 30-year cycle.
Measurements taken of the ocean's temperature show that Earth is heating up. However, those higher temperatures aren't being recorded on Earth's surface.
So where is the extra heat going? The study, led by the University of Washington, believes it's going into the depths of the Atlantic Ocean. After observing deep-sea temperatures of over 6,500 feet of the Atlantic Ocean, researchers noticed more heat being trapped there around 1999, when the rapid warming of the Earth's surface slowed down.
The slow current in the Atlantic that carries heat to and from the poles, started speeding up around the year 2000. This is a result of the water becoming saltier and denser, which causes it to sink to the bottom of the ocean and sucks the heat down into the speeding current.
After the cycle is over, the heat rises back to the surface and there's a warming trend on Earth's surface.
"There are recurrent cycles that are salinity-driven that can store heat deep in the Atlantic and Southern oceans," says Ka-Kit Tung, one of the study's authors. "After 30 years of rapid warming in the warm phase, now it's time for the cool phase."
Other studies have named the Pacific Ocean as the culprit of the warming slowdown, so scientists disagree with the research done by the University of Michigan. Jet Propulsion Laboratory climate scientist Josh Willis called it an "interesting hypothesis," but urged that scientists need more data from other tools on the ocean's heat content.
Regardless of the reason behind the slowing of global warming, scientists insist that this cooler period doesn't mean that global warming isn't occurring.
"It's important to note that a pause in rising temperatures doesn't mean global warming isn't happening, says NCAR senior scientist Gerald Meehl. "Global warming hasn't stopped, it has temporarily shifted to the subsurface ocean."