Experiments related to twentieth century historical climate changes and the twenty-first century scenario are performed with the latest version of the MRI climate model, MRI-CGCM2.3. The model reproduces globally averaged surface air temperature (SAT) variations in the twentieth century with satisfactory agreement with interdecadal changes of the observed trend, as well as with the overall SAT increase of 0.5°C at the present-day compared to the pre-industrial level. The globally averaged SAT rises 2.4°C in the late twenty-first century in the experiment for scenario A1B of the Special Report on Emissions Scenarios (SRES) by the Intergovernmental Panel on Climate Change (IPCC). The spatial structures of the simulated trends for the late twentieth century are validated in various atmospheric fields through comparisons with observed data, which indicate that the model demonstrates reasonable agreement with the observed trend in each field. Most of the simulated changes for the twenty-first century reveal spatial patterns similar to those in the trends that appeared in the late twentieth century. The simulated trend patterns of the sea-level pressure (SLP) in both hemispheres bear a resemblance to the observed trends, with each spatial structure reminiscent of the annular modes in the northern and southern hemispheres (NAM and SAM). These SLP trend patterns are consistent with the trends in the SAT, precipitation, and zonal mean zonal wind fields, as in the NAM and SAM. The coherent trend structures of these fields are projected to be enhanced in twenty-first century climate changes. Changes of ocean and sea-ice in association with these atmospheric changes are also described.