Hidden Warming Effects of Cloud Cycle Errors in Climate Models

摘要

Clouds' efficiency at reflecting solar radiation and trapping the terrestrialone is strongly modulated by their diurnal cycle. Much attention has been paidto mean cloud properties due to their critical role in climate projections;however, less research has been devoted to their diurnal cycle. Here, wequantify the mean, amplitude, and phase of the cloud cycles in current climatemodels and compare them with satellite observations and reanalysis data. Whilethe mean values appear to be reliable, the amplitude and phase of the diurnalcycles of clouds show marked inconsistencies, especially over land. We showthat, to compensate for the increased net radiation input implied by sucherrors, an overestimation of the cloud liquid water path may be introducedduring calibration of climate models to keep temperatures in line withobservations. These discrepancies are likely to be related to cloudparametrization problems in relation to atmospheric convection.