A recent study suggests that global oceans are warming at mind-boggling rates since they absorbed more than 90 percent of the heat generated by the greenhouse gas effect and 30 percent of the excess carbon dioxide released in the atmosphere by human activities since pre-industrial times.
Scientists from National Oceanic and Atmospheric Administration (NOAA) and the Lawrence Livermore National Laboratory found that it took our planet’s ocean water thousands of years before the industrial era to warm as much as it did in the last 20 years.
The team of researchers also found that while 35 percent of the excess heat is usually stored at depths of 2,300 feet (700 meter) or more, the bulk must be found in the deeper layers. The situation is unseen since two decades ago just 20 percent of the excess heat was stored in those depths.
The study, which was published this week in the journal Nature Climate Change, sought to zoom in on the excess heat that is trapped by global oceans.
Study authors explained that oceans have a much larger capacity of storing heat than the atmosphere. About 90 percent of heat generated through greenhouse gas emissions is trapped by the world’s oceans. Five years ago, a report showed that the Southern Ocean was able to absorb 1.2 billion tons of carbon per year, which is about how much Europe produces in a year.
In the recent research, investigators studied heat variations at various depths in multiple sites across the world. They also sifted through similar data dating back to 1865.
For superficial layers, i.e. those located within 2,300 feet from the oceanic surface, the team used data collected by HMS Challenger expedition, which measured heat content in ocean water in the mid-1870s.
More up-to-date data was gathered by a fleet of “Deep Argo” robots, which can take water samples and measure heat content at far greater depths than the 1870s expedition.
Peter Gleckler, senior researcher involved in the study, explained that old and new data suggested that ocean water temperature rose by “several tenths of a degree” since the pre-industrial times. Gleckler noted that while this may not seem much, it is a ‘huge increase’ at historical scale.
Gleckler added that global warming might be even worse as most studies had often overlooked the amount of trapped heat within the oceans’ deepest layers. He believes that we can fully understand the phenomenon if we scrutinize not only the surface, but also the oceanic depths.
“We can’t just look at the upper ocean anymore, we need to look deeper,”
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