A recent nature study has observed that half of the warming of the world’s oceans, which started in the pre-industrial era, happened over the past 20 years. The study has found that a considerable volume of the extra heat can be found under great depths of the ocean.

US scientists observed that 35 percent of the extra heat is retained at depths below 700 meters. This indicates that more heat could be trapped at greater depths compared with the situation 20 years ago. The report also brought to the notice the amount of heat being absorbed by the oceans.

“The ocean has stored more than 90 percent of the Earth’s uptake of heat associated with greenhouse-gas-attributed warming since 1970,” the report said. It added that the observed changes in the global ocean heat content primarily focused on the temperature measurement of the upper ocean, as not much is known about the difference between temperature measurement and model simulations below 700 meters.

The Guardian reported that the scientists at the Lawrence Livermore National Laboratory studied the changes in temperature at varying depths of the ocean by referring to the data and model available since 1865.

Almost 30 percent of the carbon dioxide produced by consumption of fossil fuel has been absorbed by the oceans. The Southern Ocean has sopped up 1.2 billion of carbon, which is equivalent to the annual carbon output of the European Union, in 2011 alone.

“In recent decades the ocean has continued to warm substantially, and with time the warming signal is reaching deeper into the ocean,” Common Dreams quoted lead author Peter Gleckler, a scientist with Lawrence Livermore National Laboratory (LLNL), as saying. “The takeaway is that the rate, at which the global ocean is absorbing excess heat, has rapidly increased—so that in more recent times since 1997, it has absorbed as much heat as it took over 100 [years] to absorb. That is alarming.”