Recent high resolution models consistently show that the global tropical cyclone (TC) frequency will decrease in the future due to global warming. In order to clarify the mechanism of TC frequency changes due to global warming, two experiments have been conducted, in addition to a present climate experiment (HPA experiment) and a future climate experiment (HFA experiment). In one experiment (CO2F experiment), future values of CO2 and other greenhouse gas (GHG) concentrations are used with present value of sea surface temperature (SST), while in the other experiment (SSTF experiment), future value of SST is used with present values of CO2 and other GHG concentrations. The global TC frequency in HFA experiment is 25% less than that of HPA experiment, while the global TC frequencies in CO2F experiment and SSTF experiment are 9% and 18% less than that of HPA experiment, respectively. These results are consistent with a previous study, although the previous study concluded that CO2 increase effect on the TC frequency change is larger than the SST increase effect, while in the present study CO2 increase effect is smaller. We have noted that the tropical precipitation decreases in the CO2F experiment compared to HPA experiment, while it increases in the SSTF experiment. Despite the opposite changes in the precipitation, both experiments show a significant decrease in upward mass flux and reduction in TC frequency. This result supports the idea that the reduction of TC frequency is closely related to a reduction of upward mass flux as indicated by some previous studies.