Aerosols
How North Atlantic aerosols steered Sahel rain
Open access · cc by · source: Europe PMC
Fixing aerosols at 1920 levels removes the observed multidecadal Sahel drought–recovery cycle that tracks North Atlantic SST.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Fixing aerosols at 1920 levels removes the observed multidecadal Sahel drought–recovery cycle that tracks North Atlantic SST.
Evidence for the claim as stated.
Fixing aerosols in CESM1, then comparing CanESM2-LE and an eight-model CMIP6 mean with HadISST/NOAA SST and CRU rain, shows that the 1925–1955 wet, 1955–1985 dry, then wet Sahel/NASST swing vanishes without evolving aerosols. NASST correlates with net surface energy (r = 0.90) and sulfate burden (r = −0.82). The CMIP6 mean does not fully kill internal variability; aerosol–cloud physics remains the main spread source.
Evidence for the claim as stated.
Fixing one forcing in a large ensemble can test a mechanism. CESM1 all-forcing versus aerosol-fixed and GHG-fixed runs, compared with CanESM2-LE and CMIP6, showed that the 20th-century North Atlantic SST and Sahel rainfall swing vanishes without evolving aerosols; NASST correlated with sulfate burden (r = −0.82) and net surface energy (r = 0.90).
Evidence for the claim as stated.
Study at a glance
- Design
- Computational / modelling — CESM1 large-ensemble all-forcing versus aerosol-fixed and GHG-fixed runs compared with observations
- N
- CESM1-LE, CanESM2-LE, and CMIP6 plus HadISST/NOAA SST and CRU rainfall
- Population
- Twentieth-century Sahel rainfall and North Atlantic SST
- Outcome
- Fixing aerosols at 1920 levels removes the observed multidecadal Sahel drought–recovery cycle that tracks North Atlantic SST
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
How North Atlantic aerosols steered Sahel rain
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
All-forcing CESM1-LE has 40 members from 1920 to 2005.
The all‐forcing experiment includes 40 ensemble members, forced with historical external forcing from 1920 to 2005.
Do GHG-only CMIP6 runs reproduce the pattern?
indicating that anthropogenic aerosol changes cause this multidecadal variability.
Key findings
Detrended NASST and Sahel rain share a 1925–1955 wet, 1955–1985 dry, then wet pattern that vanishes without evolving aerosols. NASST correlates with net surface energy (r=0.90) and sulfate burden (r=−0.82); aerosol–cloud interactions dominate the NASST effect.
Methodology
Authors compared CESM1 large-ensemble all-forcing, aerosol-fixed, and GHG-fixed runs with CanESM2-LE, CMIP6, HadISST/NOAA SST, and CRU rainfall, linking sulfate, North Atlantic energy fluxes, SST, ITCZ, and Sahel rain.
Limitations
Eight-model CMIP6 means do not fully kill internal variability; aerosol–cloud physics is the main model-spread source, so future Sahel rain still hinges on uncertain ACI.
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