Oceans Trapped Startling Amount of Heat in Last 18 Years
The oceans have soaked up as much heat from global warming over the last two decades as during the preceding 130 years, a study by scientists has found. →
The oceans have soaked up as much heat from global warming over the last two decades as during the preceding 130 years, a study by U.S. scientists has found.
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, the 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 meters 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, the study said.
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 1.2 miles deep -- so-called Argo floats scattered across the oceans.
Absorption ‘could play havoc with weather'
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.
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.
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," Mr Shepherd said.
At current rates, Earth is on track for warming of about three degrees Celsius by the end of the century.
There is growing scientific evidence that even an increase of 2C - 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.
The effects of global warming are frequently projected decades into the future, but two recent reports -- one from the
and the other
-- put into sharp focus visible consequences of our warming planet. An increase in temperature, extreme weather, loss of ice and rising sea level are just a few of changes we can measure right now. Let's take a look at some of the most concerning trends.
Glaciers are shrinking worldwide and permafrost is thawing in high-latitude and high-elevation areas, reports this year's Fifth Assessment Report from the Intergovernmental Panel on Climate Change.
Only a few extinctions are attributed to climate change, reports the IPCC, but climate change that occurred much more slowly, over millions of years, caused major ecosystem shifts and species extinctions. Land and sea animals are changing their geographic ranges and migratory patterns due to climate change.
Sea level around the world has increased by about 8 inches since 1880, reports the 2014 National Climate Assessment, which projects a 1 to 4 foot rise by the end of the century.
Excess CO2 is dissolving in the ocean and decreasing the pH of seawater. The ocean is about 30 percent more acidic than it was in pre-industrial times. More acidity in the oceans makes it harder for animals to form calcium carbonate shells and skeletons and erodes coral reefs.
The probability of a Sandy-like storm deluging New York, New Jersey and other parts of the East Coast has nearly doubled compared to 1950, according to the American Meteorological Society. Even weaker storms will be more damaging now than they were 10 years ago because of rising sea levels. Superstorm Sandy cost the nation $65 billion, according to the 2014 National Climate Assessment, and 2012's Hurricane Isaac cost $2.3 billion.
The global sea level rises along with the temperature for two major reasons. For one, heat causes water to expand, which causes the existing water to take up more space and encroach on the coast. At the same time, ice at the poles and in glaciers melts and increases the amount of water in the oceans.
Across the United States, heavy downpours are on the rise, especially in the Northeast and Midwest. Increases in extreme precipitation are expected for all U.S. regions, reports the 2014 National Climate Assessment.
The most recent IPCC report states with "very high confidence" that current climate-related extremes like heat waves, droughts, floods, cyclones and wildfires are showing that countries around the world, at all development levels, are significantly unprepared. The American Meteorological Society estimates that approximately 35 percent of the extreme heat in the eastern United States between March and May 2012 resulted from human activities' effects on climate. The AMS warned that deadly heat waves will become four times more likely in the north-central and northeastern United States as the planet continues to warm.