Changes in Anthropogenic PM2.5 and the Resulting Global Climate Effects Under the RCP4.5 and RCP8.5 Scenarios by 2050

Using an aerosolclimate model, we studied the temporal and spatial variations of anthropogenic PM2.5 (aerodynamic diameter <= 2.5 mu m) and coarse particulate matter (CPM; aerodynamic diameter >2.5 mu m) under Representative Concentration Pathway (RCP) 4.5 and RCP8.5 scenarios from 2014 to 2050. The corresponding radiative forcing and climate responses were also explored. The PM2.5 burden decreases over most continents, especially East Asia. The CPM particles increase over northern Asia, North America, and central Africa, in contrast to decrease over most regions of East Asia and North Africa. Relative to 2014, the global annual mean effective radiative forcing due to changes in PM2.5 and CPM burden are 1.17 (1.10) and -0.06 (-0.07) W m(-2) under RCP4.5 (RCP8.5), respectively. The reduction in PM2.5 burden leads to apparent warming, especially over high latitudes of the Northern Hemisphere, with global annual mean surface air temperature increasing by 1.25 K under RCP4.5, and 1.22 K under RCP8.5. In contrast, changes in CPM result in apparent cooling over North America and northern Asia, with global annual mean changes in surface air temperature of 0.10 K for both scenarios. The Northern Hemisphere Hadley cell weakens and moves northward due to changes in PM2.5 after 2014, whereas the corresponding circulation in the Southern Hemisphere is strengthened, with the Intertropical Convergence Zone shifting to 10 degrees N. Global annual mean precipitation increases by 0.10 mm day(-1) under both scenarios. Generally, anthropogenic PM2.5 contributes significantly to future changes in radiative forcing and climate.