HR: 11:00h
AN: A52B-03    [Abstracts]
TI: Assessing global radiative forcing due to regional emissions of tropospheric ozone precursors: a step towards climate credit for ozone reductions
AU: * Mauzerall, D L
EM: mauzeral@princeton.edu
AF: Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544 United States
AU: Naik, V
EM: naik@princeton.edu
AF: Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544 United States
AU: Horowitz, L W
EM: larry.horowitz@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, NJ 08542 United States
AU: Schwarzkopf, D
EM: dan.schwarzkopf@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, NJ 08542 United States
AU: Ramaswamy, V
EM: V.Ramaswamy@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, NJ 08542 United States
AU: Oppenheimer, M
EM: omichael@princeton.edu
AF: Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544 United States
AB: The global distribution of tropospheric ozone (O3) depends on the location of emissions of its precursors in addition to other chemical and dynamical factors. Global O3 forcing is, therefore, a sum of regional forcings arising from emissions of precursors from different countries. The Kyoto Protocol does not include ozone as a greenhouse gas, and emission reductions of ozone precursors made under Kyoto or any similar agreement would presently receive no credit. Unlike gases which are directly emitted, to include O3 in a climate agreement, reductions in its chemical precursors must be given credit and the resulting change in radiative forcing must be determined. In this study, using a global chemical tracer model (MOZART-2) we quantitatively estimate the contribution of emissions of anthropogenic O3 precursors (NOx, CO, and NMHCs) from specific countries and regions of the world to global O3 distributions. We then estimate the global radiative forcing on climate due to changes in O3 and CH4 resulting from the regional reductions of NOx emissions alone and combined reductions of NOx, CO, and NMHCs using a global radiation model from the Geophysical Fluid Dynamics Laboratory. Our results show that O3 production and resulting distributions depend strongly on the geographical location of emissions of its precursors. For reductions of NOx emissions alone, decreases in radiative forcing due to O3 reductions per molecule of NOx reduced are largest for tropical regions (Southeast Asia, South America, and the Indian subcontinent) and smallest for emission reductions from mid- and high latitude regions (Europe, the Former Soviet Union and North America). However, due to increases in CH4 concentrations resulting from the O3 decreases, the net radiative forcing from NOx emission reductions alone is positive for all regions except Southeast Asia and the Indian subcontinent. In contrast, for combined reductions of anthropogenic emissions of NOx, CO, and NMHCs, changes in O3 and CH4 result in a net reduction in radiative forcing for all regions we consider. Our key finding is that in order to reduce climate forcing resulting from emission of tropospheric O3 precursors, it is necessary to consider simultaneous reductions of CO, NMHCs, and NOx; NOx emission reductions alone are not sufficient to guarantee a reduction in climate forcing when the full effect of changes in O3 and CH4 are taken into account.
UR: http://www.wws.princeton.edu/mauzerall
DE: 0360 Transmission and scattering of radiation
DE: 0365 Troposphere--composition and chemistry
DE: 6620 Science policy
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly