Study Rectifies 135-Year-Old Ocean Global Warming Data

When the HMS Challenger set sail 135 years ago, it studied ocean temperatures along the way by dropping thermometers attached to Italian hemp ropes hundreds of meters deep – an effort that has been used as a baseline for global warming in oceans since pre-industrial times. However, a new study – combining the work of the HMS Challenger with modern-era climate science models – has found we may be significantly under-estimating global warming’s impact and heat content in the oceans.

The US and Australian researchers have discovered that 40% of the sea level rise has come from expansion of sea water caused by warming, and the remaining 60% has derived from melting ice sheets and glaciers. According to Dr. Will Hobbs, the study’s lead author and a researcher at the University of Tasmania’s Institute for Marine and Antarctic Studies, ‘Our research revealed warming of the planet can be clearly detected since 1873 and that our oceans continue to absorb the great majority of this heat. Currently scientists estimate the oceans absorb more than 90% of the heat trapped by greenhouse gases, and we attribute the global warming to anthropogenic causes.’

Josh Willis, a study co-author who is a climate scientist at NASA’s Jet Propulsion Laboratory, explained, ‘The key to this research was to determine the range of uncertainty for the measurements taken by the crew of the Challenger. After we had taken all these uncertainties into account, it became apparent that the rate of warming we saw across the oceans far exceeded the degree of uncertainty around the measurements. So, while the uncertainty was large, the warming signal detected was far greater.’

However, Hobbs noted, ‘Because we took the most conservative outcome, we are likely to have underestimated the true temperature rise. A simple analysis of our results suggests we may have underestimated the warming by as much as 17%. In fact many of the stations most prone to bias were in the Eastern Pacific – a region showing one of the strongest ocean warming trends – so the true warming may be even larger than that.’ He added, ‘This research adds yet another suite of compelling data that shows human activity continues to have a dramatic influence on the Earth’s climate.’

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