Green Sahara may have Diminished Atlantic Tropical Cyclones: Insights from the Mid-Holocene

While anthropogenic warming is projected to green the Sahara region, the potential impacts on tropical cyclone (TC) activity remain poorly understood. Here we examine the mid-Holocene (MH; ~6 ka BP) Sahara greening (characterized by expanded vegetation and substantially reduced dust emissions) as a potential analog for the future, combining high-resolution global atmospheric model simulations with paleoclimate proxy records. The simulation results demonstrate that Sahara greening dramatically reduced North Atlantic (NA) TC frequency to near-zero levels while causing minimal changes in other basins. In simulations without Sahara greening, the MH TC distribution resembles the pre-industrial pattern, albeit with an eastward shift of TC genesis in the North Pacific. The greening-induced TC suppression primarily resulted from two mechanisms: (1) enhanced vertical wind shear off West Africa and (2) reduced low-level moisture over the western tropical NA. These findings align well with reconstructed NA TC variability and may provide important insights into future TC activity under potential Sahara greening scenarios.