Oceans heat fast, even with slower warming at Earth's surface

Alister Doyle Reuters Yahoo News 19 Jan 16;

OSLO (Reuters) - 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.

Understanding ocean heat "is vital to improving projections of how much and how fast the Earth will warm and seas rise in the future," LLNL wrote in a statement. Most of the extra heat from man-made global warming ends up in the oceans.

The scientists said it was hard to judge the role of ocean heat in what the United Nations panel of climate scientists calls a "hiatus" in surface warming, which had heartened those who doubt big man-made impact on the climate.

"The 'hiatus' is a surface phenomenon. The Earth is still warming, and the oceans have been taking up the bulk of that heat," Matt Palmer, a climate scientist at the British Met Office Hadley Centre who was not involved in the study, wrote in a statement.

John Shepherd, of the University of Southampton, said it was unclear if the extra heat absorbed by the oceans would return to the atmosphere or stay in the depths. "It's certainly not a cure for climate change, nor any reason to be less concerned with it," he said in a statement on ocean warming.

Last month, almost 200 governments agreed a deal in Paris meant as a turning point from fossil fuels, blamed for causing more heat waves, downpours and rising sea levels.

(Editing by Jeremy Gaunt)

Study: Man-made heat put in oceans has doubled since 1997
SETH BORENSTEIN Associated Press Yahoo News 19 Jan 16;

WASHINGTON (AP) — The amount of man-made heat energy absorbed by the seas has doubled since 1997, a study released Monday showed.
Scientists have long known that more than 90 percent of the heat energy from man-made global warming goes into the world's oceans instead of the ground. And they've seen ocean heat content rise in recent years. But the new study, using ocean-observing data that goes back to the British research ship Challenger in the 1870s and including high-tech modern underwater monitors and computer models, tracked how much man-made heat has been buried in the oceans in the past 150 years.

The world's oceans absorbed approximately 150 zettajoules of energy from 1865 to 1997, and then absorbed about another 150 in the next 18 years, according to a study published Monday in the journal Nature Climate Change.

To put that in perspective, if you exploded one atomic bomb the size of the one that dropped on Hiroshima every second for a year, the total energy released would be 2 zettajoules. So since 1997, Earth's oceans have absorbed man-made heat energy equivalent to a Hiroshima-style bomb being exploded every second for 75 straight years.

"The changes we're talking about, they are really, really big numbers," said study co-author Paul Durack, an oceanographer at the Lawrence Livermore National Lab in California. "They are nonhuman numbers."

Because there are decades when good data wasn't available and computer simulations are involved, the overall figures are rough but still are reliable, the study's authors said. Most of the added heat has been trapped in the upper 2,300 feet, but with every year the deeper oceans also are absorbing more energy, they said.

But the study's authors and outside experts say it's not the raw numbers that bother them. It's how fast those numbers are increasing.

"After 2000 in particular the rate of change is really starting to ramp up," Durack said.

This means the amount of energy being trapped in Earth's climate system as a whole is accelerating, the study's lead author Peter Gleckler, a climate scientist at Lawrence Livermore, said.

Because the oceans are so vast and cold, the absorbed heat raises temperatures by only a few tenths of a degree, but the importance is the energy balance, Gleckler and his colleagues said. When oceans absorb all that heat it keeps the surface from getting even warmer from the heat-trapping gases spewed by the burning of coal, oil and gas, the scientists said.

The warmer the oceans get, the less heat they can absorb and the more heat stays in the air and on land surface, the study's co-author, Chris Forest at Pennsylvania State University, said.

"These finding have potentially serious consequences for life in the oceans as well as for patterns of ocean circulation, storm tracks and storm intensity," said Oregon State University marine sciences professor Jane Lubchenco, the former chief of the National Oceanic and Atmospheric Administration.

One outside scientist, Kevin Trenberth, climate analysis chief at the National Center for Atmospheric Research, also has been looking at ocean heat content and he said his ongoing work shows the Gleckler team "significantly underestimates" how much heat the ocean has absorbed.

Jeff Severinghaus at the Scripps Institute of Oceanography praised the study, saying it "provides real, hard evidence that humans are dramatically heating the planet."

Global warming strikes deep into oceans: study
Marlowe Hood AFP Yahoo News 19 Jan 16;

Paris (AFP) - The oceans have soaked up as much heat from global warming over the last two decades as during the preceding 130 years, according to a study published Monday.

While this accelerated absorption has helped keep human habitats cooler, in the long run it could be a ticking time bomb that disrupts weather and climate globally, scientists warned.

"We estimate that half of the total global ocean heat uptake since 1865 has accumulated since 1997," a team of scientists led by Peter Gleckler of the Lawrence Livermore National Laboratory in California reported.

A third of that recent build up, they found, occurred at depths of 700 metres (2,300 feet) or greater, beyond the reach of sunlight.

This may explain a pause or "hiatus" in warming observed at the sea surface since the end of the 20th century, according to the study.

Some had interpreted this as a slowdown in warming overall.

Surface waters are thought to have previously absorbed the bulk of heat taken up by the ocean. Why the ratio is changing is not fully understood.

The findings, published, in Nature Climate Change, were based in large part on observation.

The earliest data was gathered in the 19th century by the HMS Challenger expedition, a scientific foray launched by Britain's Royal Society that is often credited with laying the foundation for modern oceanography.

More recent inputs came from multi-decade ship logs, and -- for measurements up to 2,000 metres (6,500 feet) deep -- so-called Argo floats scattered across the oceans.

- Mixed blessing -

Covering two-thirds of Earth's surface, the oceans have absorbed more than 90 percent of the excess heat generated by man-made greenhouse gases.

In a stroke of luck for humankind, this has made the surface of the planet less hot than it would otherwise have been.

View galleryIce chunks are seen in the Northwest Passage in the …
Ice chunks are seen in the Northwest Passage in the Canadian High Arctic on September 23, 2015 (AFP …
But there could be severe consequences further down the road, scientists cautioned.

"It's a bit of a mixed blessing," said John Shepherd, a researcher at the University of Southampton's National Oceanography Centre, who was not involved in the study.

If the extra heat remains in the ocean it could disturb sea and atmospheric circulation, playing havoc with weather patterns, he explained.

And if it is released back into the atmosphere, it could accentuate warming already poised to punch through the threshold for dangerous impacts.

The ocean's ability to absorb surplus heat is not unlimited, and "certainly not a cure for climate change," said Shepherd.

At current rates, Earth is on track for warming of about three degrees Celsius (5.4 degrees Fahrenheit) by the end of the century.

There is growing scientific evidence that even an increase of 2 C (3.6 F) -- once considered a safe upper boundary -- could unleash severe human misery.

Matt Palmer, a climate scientist at Britain's national Met Office, said the study "shows the strengthening of the climate change signal over time, and that more of this signal is finding its way into the deep ocean."

The results showed that the so-called hiatus was merely a surface phenomenon, he added.

"The Earth is still warming, and the oceans have been taking up the bulk of that heat."

Because the carbon dioxide which drives global warming stays in the atmosphere for centuries, oceans will continue to heat up long after humanity stops spewing carbon pollution into the air.

Besides heat, the oceans are also a sink for carbon dioxide, which has caused sea water to become a quarter more acidic since the onset of the Industrial Age.

That acidification -- already at its highest level in 300 million years -- has ravaged coral reefs, and could have even broader consequences for other marine fauna and flora.

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