Oceans may be warming at a faster rate, study says

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Oceans are heating at a rate up to 40 percent faster than what was estimated a few years ago by the 2014 Intergovernmental Panel on Climate Change, or IPCC, report, according to a new study published in the journal Science.

“This study is an assessment that pulls in our own work along with other recent work that proves to give answers to how rapidly the ocean is warming that are significantly higher than in the last IPCC report,” said co-author Kevin Trenberth.

Head author Lijing Cheng of the Chinese Academy of Sciences and co-authors John Abraham of the University of St. Thomas, Zeke Hausfather of the Energy and Resources Group of UC Berkeley and Trenberth of the National Center for Atmospheric Research pulled results from four different studies conducted by independent groups of researchers.

The 2014 IPCC Fifth Assessment Report, or AR5, identified a discrepancy between climate models and observations of ocean heat content, or OHC. Oceans seemed to be warming at a slower rate than previous models had predicted, according to the 2014 report.

“Over the past five years the research community has made substantial progress in improving long-term OHC records and has identified several problems with prior OHC estimates,” Hausfather said in an email. ”Improvements include properly accounting for limitations in some older OHC instruments and taking advantage of better methods of accounting for gaps in the coverage and completeness of ocean temperature measurements.”

The presentation of four updated OHC estimates published in the past few years reflect a 40 percent faster OHC warming than the estimates featured in the IPCC AR5, according to the study.

Anthropogenic climate change stems primarily from an energy imbalance in the Earth’s climate due to higher concentrations of heat-trapping gases, according to the study. Roughly 93 percent of the energy imbalance accumulates in the ocean as increased OHC.

As oceans warm, more water evaporates into the atmosphere, which increases humidity and makes rainfall heavier, according to Abraham. Warmer oceans contribute to more rain, exacerbating the intensity of hurricanes. To determine humidity, the land rainfall is measured through the use of instruments such as rain gauges and then compared with the amount of evaporated ocean water, Abraham said.

The temperature of the top 2,000 meters of the world’s oceans will rise 0.78 degrees Celsius by the end of the century if humans continue to follow a non-interventionist approach, according to the Coupled Model Intercomparison Project Phase 5 models.

This spike in temperature would raise sea levels nearly 12 inches, in addition to ongoing thermal expansion caused by melting glaciers and ice sheets. Warmer oceans could also produce stronger storms, hurricanes and extreme precipitation, according to the study.

“The fingerprint of human influence on the climate is much easier to detect in the oceans, as it is much less affected by year-to-year natural variability than more commonly used surface temperature records,” Hausfather said in an email.

Contact Alexa VanHooser at [email protected] and follow her on Twitter at @dailycalexa.