A study of the variability of the global climate system has revealed that global ocean temperatures have increased in recent months.
“This summer has seen the highest global mean sea surface temperatures ever recorded since their systematic measuring started. Temperatures even exceed those of the record-breaking 1998 El Niño year,” says Axel Timmermann, climate scientist and professor at the International Pacific Research Center, University of Hawaii at Manoa.
Recorded ocean surface temperatures had been rising steadily alongside rising greenhouse gas concentrations. Then came the so-called Global Warming Hiatus, the period between 2000 and 2013 when sea surface temperatures stopped rising despite the continuing increase in greenhouse gas concentrations. The Hiatus raised a lot of public and scientific interest. However, as of April 2014 ocean warming has picked up speed again, according to Timmermann’s analysis.
“The 2014 global ocean warming is mostly due to the North Pacific, which has warmed far beyond any recorded value (Figure 1a) and has shifted hurricane tracks, weakened trade winds, and produced coral bleaching in the Hawaiian Islands,” explains Timmermann.
According to the research findings, several events preceded the latest upswing in ocean temperatures. In January 2014, sea surface temperatures started to rise unusually quickly in the extratropical North Pacific. Then in April and May, westerly winds pushed a huge amount of very warm water from the western Pacific eastward along the equator. This warm water has spread along the North American Pacific coast, releasing into the atmosphere enormous amounts of heat that had been confined to the Western tropical Pacific for nearly a decade.
“Record-breaking greenhouse gas concentrations and anomalously weak North Pacific summer trade winds, which usually cool the ocean surface, have contributed further to the rise in sea surface temperatures. The warm temperatures now extend in a wide swath from just north of Papua New Guinea to the Gulf of Alaska (Figure 1b),” Timmermann explains.
The current record-breaking temperatures suggest that the thirteen-year pause in ocean warming has come to an end.