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Uncertainty in preindustrial abundance of tropospheric ozone: Implications for radiative forcing calculations
Author(s) -
Mickley Loretta J.,
Jacob Daniel J.,
Rind David
Publication year - 2001
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000jd900594
Subject(s) - tropospheric ozone , radiative forcing , atmospheric sciences , troposphere , forcing (mathematics) , environmental science , ozone , climatology , isoprene , ozone layer , stratosphere , meteorology , aerosol , chemistry , geology , geography , organic chemistry , copolymer , polymer
Recent model calculations of the global mean radiative forcing from tropospheric ozone since preindustrial times fall in a relatively narrow range, from 0.3 to 0.5 W m −2 . These calculations use preindustrial ozone fields that overestimate observations available from the turn of the nineteenth century. Although there may be calibration problems with the observations, uncertainties in model estimates of preindustrial natural emissions must also be considered. We show that a global three‐dimensional model of tropospheric chemistry with reduced NO x emissions from lightning (1–2 Tg N yr −1 ) and soils (2 Tg N yr −1 ) and increased emissions of biogenic hydrocarbons can better reproduce the nineteenth century observations. The resulting global mean radiative forcing from tropospheric ozone since preindustrial times is 0.72–0.80 W m −2 , amounting to about half of the estimated CO 2 forcing. Reduction in the preindustrial lightning source accounts for two thirds of the increase in the ozone forcing. Because there is near‐total titration of OH by isoprene in the continental boundary layer of the preindustrial atmosphere, isoprene and other biogenic hydrocarbons represent significant ozone sinks. The weak or absent spring maximum in the nineteenth century observations of ozone is difficult to explain within our understanding of the natural ozone budget. Our results indicate that the uncertainty in computing radiative forcing from tropospheric ozone since preindustrial times is larger than is usually acknowledged.

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