Scientists Say New Method of Analyzing Ocean Heat Content Provides 'Key Metric' for Measuring Global Warming

New methods of measuring ocean heat levels now provide a “key metric” for determining how fast Earth is warming and how much it will warm in the future.

An international group of five climate scientists recently described the new methods – and how their measurements compare to computer models – in a study published recently in the journal Ocean Sciences.

John Abraham

John Abraham

The scientists are Lijing Cheng and Jiang Zhu from the International Center for Climate and Environment Sciences in Beijing, China; Kevin Trenberth from the National Center for Atmospheric Research in Colorado; Matthew Palmer from the Met Office Hadley Centre for Climate Science in the United Kingdom; and John Abraham from the University of St. Thomas School of Engineering.

The study, titled “Observed and Simulated Full-Depth Ocean Heat Content Changes for 1970-2005,” analyzed ocean heating throughout its full depth and used new techniques to learn about ocean temperature changes in areas where there are very few measurements.

Abraham said the study found “excellent agreement” between the new ocean heat measurements and a large group of computer models that predict global warming rates.

According to the measurements, Earth has gained 0.46 watts per square meter between 1970 and 2005. Since 1992, however, the rate has been 0.75 watts per square meter, showing an acceleration of the warming.

The global warming models, meanwhile, show a warming of 0.41 watts per square meter from 1970 through 2005, and from 1992 to 2005, the rate was 0.77 watts per square meter.

That means, Abraham said, that since 1992 the models have been within 3 percent of the actual measurements.

“In my mind, this agreement is the strongest vindication of the models ever found,” he wrote in a column recently published in the British newspaper The Guardian. “These numbers are the most accurate measurements of the rate at which the Earth is warming.”

“To put this in perspective, this is the equivalent of 5,400,000,000,000 60-watt light bulbs running continuously day and night,” Abraham wrote. “Another way to look at this is the Earth is gaining the equivalent of approximately six Hiroshima bombs of heat every second, day and night.”

Cheng said, “Ocean heat content is a vital climate indicator and is a key metric for global warming. How well ocean heating can be assessed by observations and can be simulated by climate models is a cornerstone of climate studies.

“By collecting the state-of-the-art observational ocean warming estimates and climate model results, this study gives the current status of measurements and models to better understand climate change.”