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

The rate of increase of global-mean surface air temperature (SAT _g) 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 multimodel ensembles of historical climate simulations. While the SAT_g 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 SAT_g 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. Key Points Global-mean SAT trend for 2001-2010 is barely represented by GCM ensembles Ocean heat uptake efficiency is weakening in GCMs and strengthening in nature Weakening of uptake efficiency is inevitable response of forced climate system