Sack Lunch Seminar (SLS)

Observational estimates and model simulations of global scale energy fluxes in the climate system are compared for four different spatial-temporal scales: 1. the global mean radiative balance of the climate system; 2. the cross-equatorial energy transport; 3. the poleward energy transport in each hemisphere; 4. the seasonal cycle of atmospheric heating and temperature. We demonstrate that the vast majority of the global mean planetary albedo is due to cloud reflection (88%) while surface reflection plays a secondary role (12%). The two hemispheres have nearly identical planetary albedos in the observations whereas they differ substantially in climate models. The latter leads to inter-model spread and bias in the location of the ITCZ as dictated by the atmospheric heat transport across the equator.
The poleward energy transport in climate models differs by 20% and is biased low, relative to observations, in the southern hemisphere. The inter-model spread in poleward heat transport is a consequence of the equator to pole gradient in planetary albedo which itself is due to differences in cloud reflection. The seasonal cycle of atmospheric heating is primarily due to shortwave absorption in the atmosphere and is opposed to energy exchange with the surface. This result is consistent between models and observations.