Annual Nitrous Oxide (N2O) Emissions on a 1x1 Degree Grid from the Global Emissions Inventory Activity (GEIA), IGBP/IGAC

The Global Emissions Inventory Activity (GEIA) is an activity of the
International Global Atmospheric Chemistry (IGAC) Core Project of the
International Geosphere-Biosphere Program (IGBP). The focus of GEIA
is to make global emissions available on a one degree grid.

Inventories with 1x1 degree resolution were compiled of nitrous oxide
(N2O) emissions from fertilized arable land, animal excreta,
post-clearing effects on soil emissions, fossil fuel and fuelwood
combustion and industrial N2O sources. For other sources of N2O,
including soils under natural vegetation, oceans and biomass burning,
published inventories were used. From these inventories the annual N2O
emission 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 uncertainties occur in the tropics, where small
errors in both soil and oceanic emission estimates may have large
repercussions for the zonal distributions. Although there may still be
many poorly known and unidentified N2O sources, the analysis has
resulted in improved understanding of some sources i.e.: (i) the
oceanic N2O emission may be more important than assumed in recent
global N2O budgets, with a major portion stemming from the 30o-90oS
zone; (ii) the N2O emission from animal excreta forms a significant
global source; (iii) most of the N2O from arable lands and grasslands,
including effects of synthetic fertilizers and animal excreta, comes
from the northern hemisphere; accounting for only the
synthetic-fertilizer effect on N2O emission leads to an
underestimation of the emission from arable lands; (iv) fossil fuel
combustion and industrial N2O sources are dominant in the 30o-90oN
zone, while N2O from fuelwood combustion is mainly produced in the
0o-30oN zone; (v) the estimation of enhanced N2O soil emission
following tropical forest clearing that has accounted for gradually
declining N2O fluxes, along with aging of the clearing leads to a
global emission that is significant but lower than previous estimates;
(vi) most of the N2O from coastal marine and freshwater systems, and
soil N2O emission resulting from N deposition probably comes from the
northern hemisphere.

More information about GEIA, its products, and the data
presented here can be accessed at
"http://geiacenter.org"