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Nitrous oxide (N2O)

This section presents an overview of:

  1. major trends in N2O emissions from 1970-2005,
  2. importance of different N2O emissions source categories, and
  3. emissions on 0.1 degree grid.

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1. Major trends in N2O emissions 1970-2005

Global nitrous oxide (N2O) emissions show an increase from ~7 Tg N2O in 1970 to ~9 Tg in 2005 (Figure 1). The strong inter-annual variation is mainly caused by emissions from savannah, grassland and forest fires. Emissions in industrialized countries show a small increase of emission in the period 1970-1980 (~3 Tg N2O to ~3.5 Tg N2O), followed by a decline of N2O emissions to below 1970 levels in the year 2005 (~2.7 Tg N2O). Emissions in developing countries show a continous increase over the 1970-2005 period from ~4 Tg N2O to ~3 Tg.

Figure 1: Graph: global nitrous oxide emissions by world region (1970-2005) in Tg N2O.
Figure 1: Global nitrous oxide emissions by world region (1970-2005) in Tg N2O [click to enlarge].

2. Important N2O emission source categories

Nitrous oxide emissions are dominated by agricultural activities and large scale biomass burning (Figure 2). In general, a increasing trend is occurring in the fuel combustion sector, while emissions from industrial processes show a downward trend, mainly due to developments in industrialized countries. Emissions from agriculture are increasing over time caused by rather constant emissions in industrialized countries and strong increase in emissions in developing countries. As shown in Figure 3, agricultural emissions show a strong increase due to the application of fertilizer to agricultural soils and due to grazing animals and animal manure spreading. The interannual variability of agricultural N2O emissions is caused by the annual variation in savannah burning (IPCC category 4E). Emissions from grassland and forest fires (Figure 4) show an increase over time and a strong inter-annual variability. Due to calculation of post-burn and decay emissions, the contribution of IPCC category 5 is larger than in earlier emission calculations.

Figure 2: Trends in global emissions of nitrous oxide by major source category (1970-2005) in Tg N2O.
Figure 2: Trends in global emissions of nitrous oxide by major source category (1970-2005) in Tg N2O [click to enlarge].

Figure 3: nitrous oxide emissions in IPCC category 4 in Tg N2O.
Figure 3: nitrous oxide emissions in IPCC category 4 in Tg N2O [click to enlarge].

Figure 4: nitrous oxide emissions in IPCC category 5 in Tg N2O.
Figure 4: nitrous oxide emissions in IPCC category 5 in Tg N2O [click to enlarge].

3. N2O emissions on 0.1 degree grid

Emissions by country and sector are allocated to a spatial grid of 0.1 x 0.1 degree. See methodology section for information on spatial allocation maps applied for the relevant N2O sectors. An illustration is presented below with global gridded nitrous oxide emissions (excluding aviation, and emissions from land-use, land use change and forestry).

Figure 5: Global gridded nitrous oxide emissions in the year 2005 (unit ton N2O per grid cell).
Figure 5: Global gridded nitrous oxide emissions in the year 2005 (unit ton N2O per grid cell) [click to enlarge].

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