The atmospheric dynamics of five different climate simulations with the GISS GCM are compared to investigate the changes that occur as climate warms or cools. There are two ice age simulations, the current and doubled CO2 climates, and a simulation of the warm Cretaceous. These climates have a range of global average surface air temperature of 13°C. The results are compared with those of other models, as well as to paleoclimate and recent observations. The study shows that many zonally averaged processes do not change systematically as climate changes. In particular, the January Hadley cell, jet stream, mean precipitation patterns and total atmospheric transport show surprisingly little variation among the different climate simulations. While eddy energy increases as climate cools, the effective eddy forcing of the mean zonal wind and temperature fields is not significantly greater. All these features result from balances between competing factors, and while individual processes differ in the col... Abstract The atmospheric dynamics of five different climate simulations with the GISS GCM are compared to investigate the changes that occur as climate warms or cools. There are two ice age simulations, the current and doubled CO2 climates, and a simulation of the warm Cretaceous. These climates have a range of global average surface air temperature of 13°C. The results are compared with those of other models, as well as to paleoclimate and recent observations. The study shows that many zonally averaged processes do not change systematically as climate changes. In particular, the January Hadley cell, jet stream, mean precipitation patterns and total atmospheric transport show surprisingly little variation among the different climate simulations. While eddy energy increases as climate cools, the effective eddy forcing of the mean zonal wind and temperature fields is not significantly greater. All these features result from balances between competing factors, and while individual processes differ in the col...