Published: Sun, November 04, 2018
Research | By Raquel Erickson

Oceans have absorbed more heat than previously thought, study finds

Oceans have absorbed more heat than previously thought, study finds

Earth's oceans have retained 60% more heat each year over the past quarter century than scientists thought, Laure Resplandy, a geoscientist at the New Jersey, US-based Princeton University who led the study, is quoted as saying by the Washington Post.

The study reveals that oceans around the world have absorbed heat energy that is equivalent to 150 times the amount of energy produced by humans every year...and that's only over the past 25 years.

A new report suggests that this has made seawater even warmer than we thought. But it also means that far more heat than we thought has been generated by the warming gases we have emitted.

"We thought that we got away with not a lot of warming in both the ocean and the atmosphere for the amount of Carbon dioxide that we emitted", she is quoted as saying. It says that rainfall, warm spells, and the number of "tropical nights" - when temperatures stay above 20 degrees Celsius - are all on the rise. The world has already warmed 1 Celsius since the past century.

"Imagine if the ocean was only 30 feet deep", Resplandy said. "This is a new complementary method, and the results are quite compatible with our estimates for the most part", he wrote in an email.Dr. Resplandy said her work did not upend the I.P.C.C. report's warnings that humanity has only a couple of decades to ward off some of climate change's most catastrophic effects."It doesn't change the results", she said.

As well as potentially making it more hard to keep warming below 1.5 or even 2C this century, all that extra heat going into the oceans will prompt some significant changes in the waters.

Measurements of ocean temperatures are also used to determine impacts on marine life and sea-level rise.

Since 2007, scientists have been able to rely on a system of nearly 4,000 Argo floats that record temperature and salinity in the oceans around the world.

Much of the data on ocean temperatures now relies on the Argo array - robotic devices that float at different depths, surfacing roughly every 10 days to transmit readings to satellites.

Researchers used Scripps' high-precision measurements of oxygen and Carbon dioxide in the air to determine how much heat the oceans have stored during the time span they studied. This allows them to accurately measure ocean temperatures globally, dating back to 1991, when accurate data from a global network of stations became available.

Scientists know that the ocean takes up roughly 90 percent of all the excess energy produced as the Earth warms, so knowing the actual amount of energy makes it possible to estimate the surface warming we can expect, said co-author Ralph Keeling, a Scripps Oceanography geophysicist and Resplandy's former postdoctoral adviser.

"When the ocean warms, it loses some gas to the atmosphere", said Resplandy.

Climate change is rapidly warming the world's oceans, killing off aquatic organisms - like coral reefs and kelp forests - that anchor entire ecosystems.

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