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Thursday, May 9, 2013

"Strengthening of ocean heat uptake efficiency associated with the recent climate hiatus," by Masahiro Watanabe et al., GRL (2013); doi:10.1002/grl.50541

Geophysical Research Letters,  DOI: 10.1002/grl.50541

Strengthening of ocean heat uptake efficiency associated with the recent climate hiatus

  1. Masahiro Watanabe1,*
  2. Youichi Kamae2,
  3. Masakazu Yoshimori1
  4. Akira Oka1
  5. Makiko Sato3,4
  6. Masayoshi Ishii5
  7. Takashi Mochizuki6, and
  8. Masahide Kimoto1


The rate of increase of global-mean surface air temperature (SATg) has apparently slowed during the last decade. We investigated the extent to which state-of-the-art general circulation models (GCMs) can capture this hiatus period by using multi-model ensembles of historical climate simulations. While the SATg linear trend for the last decade is not captured by their ensemble means regardless of differences in model generation and external forcing, it is barely represented by an 11-member ensemble of a GCM, suggesting an internal origin of the hiatus associated with active heat uptake by the oceans. Besides, we found opposite changes in ocean heat uptake efficiency (κ), weakening in models and strengthening in nature, which explain why the models tend to overestimate the SATg trend. The weakening of κ commonly found in GCMs seems to be an inevitable response of the climate system to global warming, suggesting the recovery from hiatus in coming decades.

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