For realistic numerical simulation of tropical cyclones (TCs), it is generally thought that high-resolution models are required. Simulating greenhouse gas-induced warming with high-resolution atmospheric general circulation models (AGCMs), sea surface temperatures (SSTs) are usually prescribed (as 'time-slice experiments'). But it is difficult to predict global-mean SST warming exactly in response to given CO2 increase (such as doubling), based on current scientific understanding. Moreover, if global climate is in a transient state after rapid CO2 increase (due to human activity, for example), global-mean SST should be significantly lower than that of equilibrium value. We have studied about decrease in simulated TC frequency due to greenhouse warming, using high-resolution AGCMs (Sugi et al. 2000; Yoshimura et al. 2001). In this study, we investigate impacts of SST warming and CO2 increase separately, using a T106 atmospheric model with prescribed SST. It is shown that change in heating rate of long-wave radiation has a significant impact on TC frequency, in response to CO2 increase.