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Abstract

The climate model MRI-CGCM3 has relatively high horizontal resolution atmosphere among the coupled models which participated in the phases 5 of the Coupled Model Intercomparison Project (CMIP5). We used precipitation of preindustrial control simulation for 100 years, historical experiment from 1850 to 2005 for 156 years and future Representative Concentration Pathways (RCP) 8.5 scenario experiment from 2006 to 2100 for 96 years simulated by the MRI-CGCM3. We defined 'tipping year' after year 2006 as the time of year when the projected 10-year mean climate of at each grid point moves to a state continuously outside the range of historical variability before year 2006. Tipping years of annual precipitation are earlier in high latitudes and central tropical Pacific where the increase of precipitation in the end of 21st century is large. In contrast, tipping year does not exist over subtropical high regions where precipitation decreases in the end of 21st century. Tipping year of intense precipitation exist globally including subtropical high regions. Over the Arabian Peninsula, tipping years of precipitation appears after 2050's. Information on the reliability of future projections is usually evaluated by ensemble simulations. However, future projection by the MRI-CGCM3 was restricted to only one realization due to the limitation of computer resources. Instead of real ensemble simulations, we created the set of virtual future projections based on the Monte Carlo method considering the natural variability of model atmosphere in the pre-industrial control simulation and future simulation. Here we proposed two kinds of measures for reliability in future projection; the standard deviation of precipitation and the probability of emergence of tipping year.

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