Changes in Anthropogenic PM2.5 and Resulting Global Climate Effects During 1850–2010

Abstract:

Using an aerosol-climate coupled model, we have investigated the climate response of anthropogenic fine particulate matter (PM_2.5, particle size smaller than 2.5 micrometer), and coarse particulate matter (CPM, particle size larger than 2.5 micrometer). The column burden of PM_2.5 has increased globally during 1850-2010, especially over South Africa and southern and eastern parts of Asia. The geographical distribution of changes in CPM was very different from that in PM_2.5, with negative growth in some areas. The global annual mean effective radiative forcings (ERFs) were -1.21 W m^-2 and -0.24 W m^-2 caused by the changes in PM_2.5 and CPM, respectively. Increases in PM_2.5 resulted in significant cooling effects on the climate, and changes in CPM column burden created slight cooling effect as well. The global annual mean surface air temperature (SAT) decreased by 0.94 K. Cooling was more apparent over Northern Hemisphere terrain and ocean at mid- and high latitudes by the increased PM_2.5, whereas the changes of SATs by increased CPM were found to be positive over high latitudes. Strong cooling due to increased PM_2.5 caused a southward shift of the Intertropical Convergence Zone (ITCZ), and the southward-shift sign was also found in that caused by CPM. The global annual mean precipitation decreased by approximately 0.09 mm day^–1 due to the increased PM_2.5. Generally, the PM_2.5 concentration changes contributed to more than 87% of the variations caused by all anthropogenic aerosols in ERF, SAT, and precipitation.