Atmospheric distributions of soot particles by current and future aircraftfleets and resulting radiative forcing on climate

One of the least understood of the possible environmental effects from trac e constituents emitted by aircraft is that of elemental carbon, soot. Distr ibutions of soot in the troposphere and stratosphere based on emissions fro m current and projected fleets of aircraft are determined in this study; th ese distributions are then used in evaluating the resulting effects on radi ative forcing on climate. The University of Illinois two-dimensional chemic al transport model of the troposphere and stratosphere is used in deriving the distributions of soot. Model results for 1992 aircraft emissions genera lly compare well with the upper tropospheric and lower stratospheric measur ements for the same pear. Estimates of atmospheric soot distributions due t o aircraft are also derived for roughly the year 2015, when a fleet of high -speed civil transports is assumed to be fully operational. Using the prese nt and future distributions of atmospheric soot, direct radiative forcing e stimates on climate were made with a modified version of the National Cente r for Atmospheric Research Community Climate Model 3 column radiation model . When compared with other forcings on climate, the determined soot distrib utions were found to have negligible impact.