Washington: A layer of the Indian and Pacific oceans, between 100-300 metres below the surface, has been accumulating more heat than previously recognized, thus temporarily hiding global warming, NASA has reported.
The study of ocean temperature measurements shows that in recent years, extra heat from greenhouse gases has been trapped in the waters of the Pacific and Indian oceans.
According to researchers, this shifting pattern of ocean heat accounts for the slowdown in the global surface temperature trend observed during the past decade.
“Greenhouse gases continued to trap extra heat but for about 10 years starting in the early 2000s, global average surface temperature stopped climbing, and even cooled a bit, explained Josh Willis from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
During the 20th century, as greenhouse gas concentrations increased and trapped more heat energy on Earth, global surface temperatures also increased.
However, in the 21st century, this pattern seemed to change temporarily.
The study, published in the journal Science, also found that the movement of warm water has affected surface temperatures.
Researchers Veronica Nieves, Willis and Bill Patzert analysed direct ocean temperature measurements, including observations from a global network of about 3,500 ocean temperature probes known as the Argo array.
These measurements show temperatures below the surface have been increasing.
The Pacific Ocean is the primary source of the subsurface warm water found in the study, though some of that water now has been pushed to the Indian Ocean.
Since 2003, unusually strong trade winds and other climatic features have been piling up warm water in the upper 1,000 feet of the western Pacific, pinning it against Asia and Australia.
“The western Pacific got so warm that some of the warm water is leaking into the Indian Ocean through the Indonesian archipelago,” Nieves noted.
Pauses of a decade or more in Earth’s average surface temperature warming have happened before in modern times, with one occurring between the mid-1940s and late 1970s.
“In the long term, there is robust evidence of unabated global warming,” Nieves said.