Global emissions inventories of acid-related compounds

Computer assessments of the atmospheric chemistry and air quality of the past, present, and future rely in part on inventories of emissions constructed on appropriate spatial and temporal scales and with appropriate chemical species. Accurate inventories are also of substantial utility to field measurement scientists and the regulatory and policy communities. The production of global emissions inventories is the task of the Global Emissions Inventory Activity (GEIA) of the International Global Atmospheric Chemistry Project (IGAC). This paper presents a summary of recent emissions inventories from GEIA and other programs for reference year 1985, with special attention directed to emissions of the acid-related compounds CO₂ (6.2 Pg C yr^–1 anthropogenic), SO_x (65 Tg S yr^–1 anthropogenic and 15 Tg S yr^–1 natural), NO_x (21 Tg N yr^–1 anthropogenic and 15–20 Tg N yr^–1 natural), HCl (55 Tg Cl yr^–1 total), and NH₃ (45 Tg N yr^–1 total). The global acid-equivalent flux of about 4.2 Teq H⁺yr^–1 is about equally attributable to SO_x and NO_x emissions. For some of the acid-related species, historic inventories are available for a century or more; all show dramatic emissions increases over that period. IPCC scenario IS92a is used here as the basis for constructing global acid-related emissions estimates for selected years to 2100; among the results are that acid equivalent emissions are expected to more than double in the coming century.