Marginal changes in the linear relationship of ENSO-PDO in the CMIP5 RCP4.5 scenario

Kwon et al. (2013) recently reported that the linear relationship of the El Nino Southern Oscillation-Pacific Decadal Oscillation (ENSO-PDO) increased significantly from the present climate to a warmer climate using the Climate Model Inter-comparison Project Phase 3 (CMIP3) multi-model datasets. We conducted the same analysis in the CMIP5 Representative Concentration Pathway (RCP) 4.5 scenario in which the increase of the atmospheric CO2 concentration from the present climate to the future climate is slightly smaller than that in the CMIP3. It is found that the linear relationship of the ENSO-PDO marginally increases in the CMIP5 RCP4.5. Our further analysis indicated that the composited sea surface temperature (SST) for the in-phase ENSO-PDO occurrence changes slightly in terms of its spatial structure in the equatorial Pacific from the present climate to the CMIP5 RCP4.5 in comparison to that in the CMIP3. Furthermore, there is little systematic change in the anomalous precipitation in the western-to-central equatorial Pacific from the present climate to the CMIP5 RCP4.5, which was in contrast to the results in the CMIP3. Concurrently, the intensification of the ENSO's associated atmospheric circulation over the North Pacific, which is associated with the increase in the ENSO-PDO linear relationship, is smaller from the present climate to the CMIP5 RCP4.5 than in the CMIP3. In addition, it is also found that the ENSO-PDO linear relationship little changes from the present climate to the CMIP5 RCP8.5, indicating that the changes in the ENSO-PDO linear relationship might be non-linear in a warmer climate.