Posted on January 11, 2019
"If you want to see where global warming is going, look in our oceans," said Zeke Hausfather of the Energy and Resources Group at the University of California, Berkeley, and co-author of the article. "Ocean warming is a very important indicator of climate change, and we have strong evidence that it is heating up faster than we thought."
"While 2018 will be the fourth hottest year on the surface, it will certainly be the hottest year ever recorded in the oceans, as it was 2017 and 2016 before that," added Hausfather. "The global warming signal is much easier to detect if it is changing in the oceans than on the surface."
The heat trapped by greenhouse gases is raising ocean temperature faster than previously thought, concludes an analysis of four recent observations of ocean warming. The results provide further evidence that previous claims of deceleration or "gap" in global warming over the past 15 years have been unfounded.
Ocean warming is a critical marker of climate change as it is estimated that 93 percent of excess solar energy trapped by greenhouse gases accumulates in the world's oceans. And, unlike surface temperatures, ocean temperatures are not affected by year-on-year variations caused by weather events like El Niño or volcanic eruptions.
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The new analysis, published Jan. 11 in the journal Science, shows that trends in ocean heat content correspond to those predicted by major climate change models and global warming is accelerating.
Assuming a business as usual scenario in which no effort was made to reduce greenhouse gas emissions, the Coupled Model Intercomparison Project 5 (CMIP5) predicts that the temperature of the world's 2,000 meters of oceans will increase by 0 , 78 degrees Celsius by the end of the century. The thermal expansion caused by this increase in temperature would raise sea levels by 30 centimeters, or about 12 inches, in addition to the already significant rise in sea level caused by the melting of glaciers and ice sheets. Warmer oceans also contribute to stronger storms, hurricanes and extreme precipitation.
The four studies, published between 2014 and 2017, provide better estimates of past trends in ocean heat content, correcting discrepancies between different types of ocean temperature measurements, and better explaining gaps in measurements over time or location.
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"The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), published in 2013, showed that major climate change models seemed to predict a much faster increase in ocean heat in the last 30 years than observed in" , said Hausfather. "That was a problem, because of all things, it's one thing we really expect the models to do."
"The fact that these corrected records now agree with climate models is encouraging in that it removes an area of great uncertainty that we had previously," he said.
A fleet of nearly 4,000 floating robots roams the world's oceans, every few days plunging to a depth of 2000 meters and measuring ocean temperature, pH, salinity and other information as they soar. This ocean monitoring battalion, called Argo, provided consistent and widespread data on ocean heat content since the mid-2000s.
Prior to Argo, ocean temperature data were scant at best, using devices called disposable ultrasound that sank to depths only once, transmitting data on ocean temperature until they settled in aquatic burials.
Three of the new studies included in the Science analysis calculated the ocean heat content back to 1970 and before using new methods to correct for calibration errors and biases in the Argo and the data of a radiographer. The fourth takes a completely different approach, using the fact that a heated ocean releases oxygen into the atmosphere to calculate ocean warming from changes in atmospheric oxygen concentrations, while other factors, such as the burning of fossil fuels, also alter levels of atmospheric oxygen.
"Scientists are continually working to improve how to interpret and analyze what was a reasonably imperfect and limited data set before the early 2000s," Hausfather said. "These four new records that have been published in recent years seem to correct many of the problems that were affecting the old records, and now they seem to agree very well with what climate models have produced."
The Daily Galaxy via UC Berkeley
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