Understanding the Response of the Seasonal Cycle of Temperature and Precipitation to Global Warming

CMIP5 models robustly predict a delay and amplification of the seasonal cycle of temperature and precipitation in the tropics in response to anthropogenic climate change. However, the mechanisms leading to this response are yet to be fully understood. Here we use an idealized GCM to investigate the seasonal cycle in the tropics over a wide range of climates for both land-like and ocean-like boundary conditions. The simulations predict a reduction in amplitude and advance of the temperature seasonal cycle with warming, opposite to that found in the CMIP5 ensemble. These results are reproduced using a simple energy balance model that represents atmospheric transport by down-gradient diffusion of moist static energy and includes a temperature dependent heat capacity. The results provide a framework for analyzing the seasonal cycle response in more complex models, and they suggest that cloud and water-vapor feedbacks, absent from our simulations, may be important in determining the seasonal cycle changes in projections of global warming.