Bibliography - M. D. Schwarzkopf

1. Naik, V., D. L. Mauzerall, L. W. Horowitz, M. D. Schwarzkopf, V. Ramaswamy, and Michael Oppenheimer, 2007: On the sensitivity of radiative forcing from biomass burning aerosols and ozone to emission location. Geophysical Research Letters, 34(L03818), doi:10.1029/2006GL028149
   [ Abstract ]

   Biomass burning is a major source of air pollutants, some of which are also climate forcing agents. We investigate the sensitivity of direct radiative forcing due to tropospheric ozone and aerosols (carbonaceous and sulfate) to a marginal reduction in their (or their precursor) emissions from major biomass burning regions. We find that the largest negative global forcing is for 10% emission reductions in tropical regions, including Africa (-4.1 mWm-2 from gas and -4.1 mWm-2 from aerosols), and South America (-3.0 mWmfrom gas and -2.8 mWmfrom aerosols). We estimate that a unit reduction in the amount of biomass burned in India produces the largest negative ozone and aerosol forcing. Our analysis indicates that reducing biomass burning emissions causes negative global radiative forcing due to ozone and aerosols; however, regional differences need to be considered when evaluating controls on biomass burning to mitigate global climate change.

2. Naik, V., D. L. Mauzerall, L. W. Horowitz, M. D. Schwarzkopf, V. Ramaswamy, and Michael Oppenheimer, 2006: Net radiative forcing due to changes in regional emissions of tropospheric ozone precursors. Journal of Geophysical Research, 110(D24306), doi:10.1029/2005JD005908
   [ Abstract ]

   The global distribution of tropospheric ozone (O₃) depends on the emission of precursors, chemistry, and transport. For small perturbations to emissions, the global radiative forcing resulting from changes in O₃ can be expressed as a sum of forcings from emission changes in different regions. Tropospheric O₃ is considered in present climate policies only through the inclusion of indirect effect of CH₄ on radiative forcing through its impact on O₃ concentrations. The short-lived O₃ precursors (NO_x, CO, and NMHCs) are not directly included in the Kyoto Protocol or any similar climate mitigation agreement. In this study, we quantify the global radiative forcing resulting from a marginal reduction (10%) in anthropogenic emissions of NO_x alone from nine geographic regions and a combined marginal reduction in NO_x, CO, and NMHCs emissions from three regions. We simulate, using the global chemistry transport model MOZART-2, the change in the distribution of global O₃ resulting from these emission reductions. In addition to the short-term reduction in O₃, these emission reductions also increase CH₄ concentrations (by decreasing OH); this increase in CH₄ in turn counteracts part of the initial reduction in O₃ concentrations. We calculate the global radiative forcing resulting from the regional emission reductions, accounting for changes in both O₃ and CH₄. Our results show that changes in O₃ production and resulting distribution depend strongly on the geographical location of the reduction in precursor emissions. We find that the global O₃ distribution and radiative forcing are most sensitive to changes in precursor emissions from tropical regions and least sensitive to changes from midlatitude and high-latitude regions. Changes in CH₄ and O₃ concentrations resulting from NO_x emission reductions alone produce offsetting changes in radiative forcing, leaving a small positive residual forcing (warming) for all regions. In contrast, for combined reductions of anthropogenic emissions of NO_x, CO, and NMHCs, changes in O₃ and CH₄ concentrations result in a net negative radiative forcing (cooling). Thus we conclude that simultaneous reductions of CO, NMHCs, and NO_x lead to a net reduction in radiative forcing due to resulting changes in tropospheric O₃ and CH₄ while reductions in NO_x emissions alone do not.

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