Preindustrial-to-present-day radiative forcing by tropospheric ozone from improved simulations with the GISS chemistry-climate GCM D. T. Shindell, G. Faluvegi, and N. Bell NASA Goddard Institute for Space Studies, and Center for Climate Systems Research, Columbia University, New York, New York, USA
Abstract. Improved estimates of the radiative forcing from tropospheric ozone increases
since the preindustrial have been calculated with the tropospheric chemistry
model used at the Goddard Institute for Space Studies (GISS) within the GISS
general circulation model (GCM). The chemistry in this model has been expanded
to include simplified representations of peroxyacetylnitrates and non-methane
hydrocarbons in addition to background NOx-HOx-Ox-CO-CH4
chemistry. The GCM has improved resolution and physics in the boundary layer, improved
resolution near the tropopause, and now contains a full representation of stratospheric
dynamics. Simulations of present-day conditions show that this coupled chemistry-climate
model is better able to reproduce observed tropospheric ozone, especially in the
tropopause region, which is critical to climate forcing. Comparison with preindustrial
simulations gives a global annual average radiative forcing due to tropospheric ozone
increases of 0.30 W/m2 with standard assumptions for preindustrial emissions.
Locally, the forcing reaches more than 0.8 W/m2 in parts of the northern subtropics
during spring and summer, and is more than 0.6 W/m2 through nearly all the
Northern subtropics and mid-latitudes during summer. An alternative preindustrial
simulation with soil NOx emissions reduced by two-thirds and emissions of
isoprene, paraffins and alkenes from vegetation increased by 50% gives a forcing
of 0.33 W/m2. Given the large uncertainties in preindustrial ozone amounts, the
true value may lie well outside this range.
Citation: Shindell, D. T., Faluvegi, G., and Bell, N.: Preindustrial-to-present-day radiative forcing by tropospheric ozone from improved simulations with the GISS chemistry-climate GCM, Atmos. Chem. Phys., 3, 1675-1702, doi:10.5194/acp-3-1675-2003, 2003.