Oceanic Influence and Lapse Rate Changes Dominate the Recent Amplified Saharan Warming

The surface air temperature (SAT) over the Sahara Desert has increased at a much faster rate than other tropical and subtropical regions in recent decades, which is termed Desert Amplification (DA). However, there is a lack of agreement on the relative roles of direct greenhouse gas (GHG) forcing and remote sea surface temperature (SST) change in the Saharan warming. By forcing an atmospheric general circulation model with the observed time-varying SST and GHG individually and in combination, this study examines the impact of each type of forcing agent in the observed Saharan warming during boreal warm season from 1979 to 2020. It is found that the remote SST changes explain a large portion of the observed warming, while the effect of direct GHG radiative forcing is almost negligible. A local energy budget analysis based on radiative kernels is performed to investigate the mechanism through which the remote SST change drives the Saharan warming. The result highlights the key role of the atmospheric horizontal energy transport (AHET) anomaly and lapse rate feedback in DA. The dominant role of the change in AHET is consistent with previous studies that found that as the SST increases, more heat is transported from the ocean to the land and warms the land surface. The positive lapse rate feedback is attributed to the bottom-heavy warming profile in the Sahara, which is different from the average tropics. We conclude that DA is mainly controlled remotely by warmer SSTs and cannot be understood as a local response to the GHG radiative forcing.