Increased hurricane intensities with CO2-induced warming as simulated using the GFDL hurricane prediction system

The impact of CO 2 -induced global warming on the intensities of strong hurricanes is investigated using the GFDL regional high-resolution hurricane prediction system. The large-scale initial conditions and boundary conditions for the regional model experiments, including SSTs, are derived from control and transient CO 2 increase experiments with the GFDL R30-resolution global coupled climate model. In a case study approach, 51 northwest Paci"c storm cases derived from the global model under present-day climate conditions are simulated with the regional model, along with 51 storm cases for high CO 2 conditions. For each case, the regional model is integrated forward for "ve days without ocean coupling. The high CO 2 storms, with SSTs warmer by about 2.2 3C on average and higher environmental convective available potential energy (CAPE), are more intense than the control storms by about 3}7 m/s (5%}11%) for surface wind speed and 7 to 24 hPa for central surface pressure. The simulated intensity increases are statistically signi"cant according to most of the statistical tests conducted and are robust to changes in storm initialization methods. Near-storm precipitation is 28% greater in the high CO 2 sample. In terms of storm tracks, the high CO 2 sample is quite similar to the control. The mean radius of hurricane force winds is 2 to 3% greater for the composite high CO 2 storm than for the control, and the high CO 2 storms penetrate slightly higher into the upper troposphere. More idealized experiments were also performed in which an initial storm disturbance was embedded in highly simpli"ed #ow "elds using time mean temperature and moisture conditions from the global climate model. These idealized experiments support the case study results and suggest that, in terms of thermodynamic in#uences, the results for the NW Paci"c basin are qualitatively applicable to other tropical storm basins.