Impact of the Warming Pattern on Global Energetics

The warming pattern due to higher greenhouse gas concentrations is expected to affect the global atmospheric energetics mainly via changes in the (i) meridional temperature gradient and (ii) mean static stability. Changes in surface meridional temperature gradients have been previously regarded as the determining feature for the energetics response, but recent studies suggest that changes in mean static stability may be more relevant than previously thought. This study aims to determine the relative importance of these two effects by comparing the energetics responses due to different warming patterns using a fully coupled atmosphere ocean general circulation model. By means of an additional diabatic forcing, experiments with different warming patterns are obtained: one with a 2xCO(2)-like pattern that validates the method, one with only the tropical upper-tropospheric warming, and one with only the high-latitude surface warming. The study's findings suggest that the dominant aspect of the warming pattern that alters the global atmospheric energetics is not its associated meridional temperature gradient changes, but the mean static stability changes. The tropical upper warming weakens the energetics by increasing the mean static stability, whereas the surface warming strengthens it by reducing the mean static stability. The combined 2xCO(2)-like response is dominated by the tropical upper-tropospheric warming effect, hence the weaker energetic activity. Eddy kinetic energy changes consistently, but the two opposite responses nearly cancel each other in the 2xCO(2) case. Therefore, estimates of future changes in storminess may be particularly sensitive to the relative magnitude of the main features of the simulated warming pattern.