Global warming began in oceans 135 years ago, suggests study
A study of temperature recordings from the 1870s suggests that the oceans began warming more than 100 years ago, much earlier than previously believed.
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"What you are then going to see is a temperature that is a little warmer than it would have been if the line has been perfectly vertical," Roemmich said, referring to the fact that temperatures are typically warmer at shallower depths. Other Challenger errors include incorrect measurements of pressure effects on the thermometers and faulty thermometer readings, he added.Skip to next paragraph
Gallery Rising seas
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Accounting for these issues, Roemmich and his team found that, on average, global ocean temperatures increased by 0.59 degrees F (0.33 degrees C) in the upper ocean down to about 2,300 feet (700 meters). This global temperature change is twice what scientists have observed for the past 50 years, suggesting that the oceans have been warming for much longer than just a few decades.
Given that thermal expansion is believed to be a major contributor to sea-level rise, Roemmich believes that the results of the study will help scientists better understand the historical record of the rising sea levels, which have been increasing since the 19th century.
Roemmich also thinks the results have important implications for understanding the imbalance of the planet's energy budget. Previous research has shown that the Earth is absorbing more heat than it is radiating, and that 90 percent of the excess heat added to the climate system since the 1960s has been stored in the oceans. "So that means that the ocean temperature is probably the most direct measure we have of the energy imbalance of the whole climate system," he said.
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