Energy / Climate Change

October 15, 2013


Tokyo Univ. Team Finds Heat Uptake in Deep Ocean is Increasing

Keywords: Climate Change University / Research institute 

A research group led by Masahiro Watanabe, Associate Professor at the Atmosphere and Ocean Research Institute, the University of Tokyo, Japan, announced on July 22, 2013, the results of research comparing observed temperature changes to model simulation data. The results show that, while the warming of global surface air has been slowing down since 2000, heat uptake has increased in ocean waters over 700 meters in depth.

The average global surface air temperature (SAT) has been increasing since the second half of the 20th century. Although the average SAT in the decade starting 2001 was higher by about 0.5 degrees Celsius than the average SAT between 1961 and 1990, the increase was only 0.03 degrees during those ten years. Such a standstill state is being called a climate "hiatus."

Watanabe's group is suggesting that the apparent stop of global warming has resulted from increased ocean heat uptake, indicating the possibility that the current climate hiatus may only be temporary. In addition, its analysis of the patterns of hiatuses resulting from natural fluctuations, using climate change simulations based on the latest global climate models, found that sea surface temperature variations resembled the negative phase of the Pacific Decadal Oscillation. These results suggest that the current hiatus may at least partially be the result of natural climate fluctuations.

The results offer some important hints for making more accurate estimates of the future increase in global SAT caused by anthropomorphic climate change.