Impact of global warming on the interannual and interdecadal climate modesin a coupled GCM

In this study, we investigated the impact of global warming on the variabil ities of large-scale interannual and interdecadal climate modes and telecon nection patterns with two long-term integrations of the coupled general cir culation model of ECHAM4/OPYC3 at the Max-Planck-Institute for Meteorology, Hamburg. One is the control (CTRL) run with fixed present-day; concentrati ons of greenhouse gases. The other experiment is a simulation of transient greenhouse warming, named GHG run. In the GHG run the averaged geopotential height at 500 hPa is increased significantly, and a negative phase of the Pacific/North American (PNA) teleconnection-like distribution pattern is in tensified. The standard deviation over the tropics thigh latitudes) is enha nced (reduced) on the interdecadal time scales and reduced (enhanced) on th e interannual time scales in the GHG run. Except for an interdecadal mode r elated to the Southern Oscillation (SO) in the GHG run, the spatial variati on patterns are similar for different (interannual + interdecadal, interann ual, and interdecadal) time scales in the GHG and CTRL runs. Spatial distri butions of the teleconnection patterns on the interannual and interdecadal time scales in the GHG run are also similar to those in the CTRL run. But s ome teleconnection patterns show linear trends and changes of variances and frequencies in the GHG run. Apart from the positive linear trend of the SO , the interdecadal modulation to the El Nino/SO cycle is enhanced during th e GHG 2040 similar to 2099. This is the result of an enhancement of the Wal ker circulation during that period. La Nino events intensify and El Nino ev ents relatively weaken during the GHG 2070 similar to 2090. It is interesti ng to note that with increasing greenhouse gas concentrations the relation between the SO and the PNA pattern is reversed significantly from a negativ e to a positive correlation on the interdecadal time scales and weakened on the interannual time scales. This suggests that the increase of the greenh ouse gas concentrations will trigger the nonstationary correlation between the SO and the PNA pattern both on the interdecadal and interannual time sc ales.