Two Distinct Modes of Climate Responses to the Anthropogenic Aerosol Forcing Changes

Abstract Unlike greenhouse gases (GHGs), anthropogenic aerosol (AA) concentrations have increased and then decreased over the past century or so, with timing of peak concentration varying in different regions. To date, it has been challenging to separate climate impact AAs from that due GHGs background internal variability. We use a pattern recognition method, taking advantage spatiotemporal covariance information, isolate forced patterns for surface ocean associated atmospheric variables all-but-one forcing Community Earth System Model ensembles. find aerosol-forced responses are dominated by two leading modes, one historical increase future decrease global mean (dominated Northern Hemisphere sources) other transition primary sources AA west east also extratropical regions tropical In particular, effect, some extent compensating exhibits zonal asymmetry temperature salinity responses. show this effect dominates total during recent decades, e.g., 1967–2007.