Af. Bouwman et al., UNCERTAINTIES IN THE GLOBAL SOURCE DISTRIBUTION OF NITROUS-OXIDE, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 100(D2), 1995, pp. 2785-2800
Inventories with 1 degrees x1 degrees resolution were compiled of nitr
ous oxide (N2O) emissions from fertilized arable land, animal excreta,
postclearing effects on soil emissions, fossil fuel and fuelwood comb
ustion, and industrial N2O sources. For other sources of N2O, includin
g soils under natural vegetation, oceans, and biomass burning, publish
ed inventories were used. From these inventories the annual N2O emissi
on was calculated for four broad latitudinal zones covering the globe.
Uncertainties were assessed by comparing variants of inventories with
source estimates inferred from inverse modeling techniques. Major unc
ertainties occur in the tropics, where small errors in both soil and o
ceanic emission estimates may have large repercussions for the zonal d
istributions. Although there may still be many poorly known and uniden
tified N2O sources, the analysis has resulted in improved understandin
g of some sources, i,e., (1) the oceanic N2O emission may be more impo
rtant than assumed in recent. global N2O budgets, with a major portion
stemming from the 30 degrees-90 degrees S zone; (2) the N2O emission
from animal excreta forms a significant global source; (3) most of the
N2O from arable lands and grasslands, including effects of synthetic
fertilizers and animal excreta, comes from the northern hemisphere; ac
counting for only the synthetic-fertilizer effect on N2O emission lead
s to an underestimation of the emission from arable lands; (4) fossil
fuel combustion and industrial N2O sources are dominant in the 30 degr
ees-90 degrees N zone, while N2O from fuelwood combustion is mainly pr
oduced in the 0 degrees-30 degrees N zone; (5) the estimation of enhan
ced N2O soil emission following tropical forest clearing that has acco
unted for gradually declining N2O fluxes, along with aging of the clea
ring leads to a global emission that is significant but lower than pre
vious estimates; (6) most of the N2O from coastal marine and freshwate
r systems and soil N2O emission resulting from N deposition probably c
omes from the northern hemisphere.