CMIP5 multi- model hindcasts for the mid-1970s shift and early 2000s hiatus and predictions for 2016-2035

Compared to uninitialized climate change projections, a multi-model ensemble from the CMIP5 10year decadal prediction experiments produces more warming during the mid-1970s climate shift and less warming in the early 2000s hiatus in both the tropical Indo-Pacific region and globally averaged surface air temperature (TAS) in closer agreement with observations. Assuming bias in TAS has stabilized in the 10year predictions, after bias adjustment, TAS anomalies for the 2016-2035 period in the 30year predictions initialized in 2006 are about 16% less than the uninitialized projections. One contributing factor for the improved climate simulation is the bias adjustment, which corrects the models' systematic errors and higher-than-observed decadal warming trend. Another important factor is the initialization with observations which constrains the ocean such that the starting points of the initialized simulations are close to the observed initial states. Key Points Multi-model initialized hindcasts simulate past climate shifts A 30 year initialized prediction shows less warming than uninitialized Initialized predictions simulate less warming than uninitialized projections