Fri, Aug 23, 2013 - Page 9 News List

Ocean could reveal the depth of human role in global warming

By Gerard Wynn  /  Reuters, LONDON

OBSERVED WARMING

The two recent papers based on Argo data found that ocean heat content had risen most rapidly in depths below 700m in the past decade.

One study ran the Argo and other historical data through models, which simulate ocean systems in a technique called reanalysis.

“The deep ocean has continued to warm, while the upper 300m OHC [ocean heat content] appears to have stabilized,” said the authors of the paper “Distinctive climate signals in reanalysis of global ocean heat content.”

DYNAMIC SYSTEMS

Reanalysis is often used to estimate values in complex, dynamic systems and inherently depends on the accuracy of the underlying model and the consistency of the observational data.

By necessity, the technique combines “inaccurate and incomplete observations with imperfect models, using methods and procedures that are technically and scientifically complex,” according to the US National Center for Atmospheric Research’s Climate Data Guide.

Its strength is that it allows scientists to combine millions of observations in a single, coherent model which can be continually improved and updated.

The reanalysis study supported another paper that used raw observations alone and found that the rate of increase in heat content was slowing only to depths of about 700m.

“Leveling is not as pronounced in our ocean heat content to 2,000m estimates, indicating that heat is being stored in the 700m to 2,000m layer,” it said.

Such studies are at the forefront of analysis of this new trove of data and may well prove right.

The implication is that emissions are indeed warming the planet as much as scientists had thought, and the heat will eventually return to the surface. However, it could take another decade of observations to be sure the oceans partly account for the recent slowdown in warming.

Gerard Wynn is a Reuters market analyst. The views expressed are his own.

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