  African dust exhibits strong variability on a range of time scales. Here we
show that the interhemispheric contrast in Atlantic SST (ICAS) drives African
dust variability on interannual, multidecadal, and millennial timescales, and a
strong anthropogenic decline of African dust in the future can be expected due
to the projected increase of the ICAS. During the recent past, the ICAS is
found to significantly correlate with various dust observations and proxies
that extend as far back as 1851. Physically, positive ICAS anomalies induce
large-scale circulation changes that push the Intertropical Convergence Zone
(ITCZ) northward and decrease surface wind speed over African dust source
regions, which reduces dust emission and transport to the tropical Atlantic.
The ICAS-ITCZ-dust relationship also finds robust support from paleo-climate
observations that span the last 17,000 years. The ICAS drive of African dust
variability is consistent with documented relationships between dust activity
and Sahel precipitation6, the North Atlantic Oscillation7, and time series of a
surface wind speed pattern over Northern Africa8, and offers a unified
framework to understand them. The ICAS-dust connection implies that human
activities that change ICAS through emitting greenhouse gases and pollutions
have affected and will continue to affect African dust. Climate models project
that anthropogenic increase of the ICAS can push the ICAS value to surpass the
highest level attained during the Holocene by the end of this century and
decrease African dust activity by as much as 60% off its current level, which
has broad consequences for aspects of the climate in the North Atlantic region
and beyond.
