Oceans Heat Fast, Even with Slower Warming at Earth's Surface

The amount of heat soaked up by the oceans has surged in the past two decades in a sign of worsening global warming despite a slowdown in temperature rises at the Earth's surface, a U.S. study showed on Monday.

The trend of warmer oceans, blamed on man-made emissions of greenhouse gases, is pushing fish stocks towards the poles, damaging coral reefs and nudging up world sea levels because water expands as it heats up.

The report, examining ocean temperatures to depths of more than 2,000 meters (6,500 ft), found that "half of the total global ocean heat uptake since 1865 has accumulated since 1997".  The year 1865 is taken as the start of wide use of fossil fuels.

And more than a third of the surge in heat in the oceans since 1997 was at depths exceeding 700 meters - a part of the ocean rarely studied, the scientists wrote in the journal Nature Climate Change.

"We expect that the deep ocean will absorb an increasing amount of heat," lead author Peter Gleckler, of the U.S. Department of Energy's Lawrence Livermore National Laboratory (LLNL) in California, told Reuters in an email.

The increase in the oceans' uptake of heat has coincided with a puzzling slowdown in the pace of temperature rises at the Earth's surface since the late 1990s, even as man-made emissions of heat-trapping gases have kept rising.

That slowdown may now be over with record temperatures in 2015 and 2014.

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