The paper states it adjusts for "ENSO, volcanic eruptions, and solar variations" and not (afaict) the changes in shipping bunker fuel that reduced atmospheric SO2 (if that is what you mean by "reduced aerosols"). Below is a summary of the topic for those who are unaware. I withhold any opinion of validity of mechanism or effect.

  Sulphur particles contained in ships' exhaust fumes had been counteracting 
  some of the warming coming from greenhouse gases. Lowering the sulfur content 
  of marine fuel weakened this masking effect, effectively giving a boost to 
  warming.