Pacific trade winds accelerated by aerosol forcing over the past two decades

The Pacific trade winds, coupled with the zonal sea surface temperature gradient in the equatorial Pacific Ocean, control regional sea levels(1), and therefore their trend is a great concern in the Pacific Rim. Over the past two decades, easterly winds have been accelerated in association with eastern tropical Pacific cooling(2). They may represent natural interdecadal variability in the Pacific(3) and possibly explain the recent global warming hiatus(4-7). However, the intensification of the winds has been the strongest ever observed in the past century(2,5,8), the reason for which is still unclear. Here we show, using multiple climate simulations for 1921-2014 by a global climate model, that approximately one-third of the trade-wind intensification for 1991-2010 can be attributed to changes in sulfate aerosols. The multidecadal sea surface temperature anomaly induced mostly by volcanic aerosols dominates in the western North Pacific, and its sign changed rapidly from negative to positive in the 1990s, coherently with Atlantic multidecadal variability(9-11). The western North Pacific warming resulted in intensification of trade winds to the west of the dateline. These trends have not contributed much to the global warming hiatus, but have greatly impacted rainfall over the western Pacific islands.