A statistical test has revealed that abrupt regional climate changes are pr
oduced in a coupled atmosphere-ocean general circulation model. Abrupt chan
ges are detected over much of the globe although the occurrence frequency i
s small over the continents. Over the tropical Pacific Ocean and northern P
acific Ocean, surface air temperature (SAT) and sea level pressure (SLP) sh
ift rapidly on decadal time scales. The regional climate changes presented
here have been classified into three types. The first type consists of stat
istically significant shifts in SLP and statistically significant shifts in
SAT which are of opposite sign, and which are reinforced through a positiv
e feedback between the atmosphere and the ocean. The second type is for tho
se occurrences where changes are of the same sign. The third type includes
those with a significant shift in only one meteorological element. The seco
nd and third types are generally generated by changes in air pressure and w
ind fields induced by changes of the first type. For example, when SLP incr
eases and sea surface temperature (SST) decreases abruptly in the tropical
Pacific Ocean, it triggers abrupt regional changes in middle and high latit
udes. The abrupt changes in the model climate have characteristics which ar
e very similar to those of observed rapid shifts. Thus, it is concluded tha
t abrupt changes are a predominant part of regional climate change on decad
al time scales.