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## N 2 O budget and uncertainties

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**N2O budget and uncertainties**IIASA, year 2000: non-energy-related 6.6 energy-related 0.5 Total (Tg N2O-N/yr) 7.1 Budget equations: N = s X0pre-industrial A + N = s X1 + T present-day N = Net natural fluxes A = Anthropogenic emissions s = stratospheric loss rate Burden ratio X1 / X0 (~ 315 / 270) IPCC 4AR, year 2000: Anthropogenic 6.7 Natural source 11.0 Trend (+1 ppb/yr) 5.0 Total (Tg N2O-N/yr) 17.7 N = (A – T) / (X1/X0 -1) N ~6*( A – T ) GEIA (1990s) energy-related 0.7 Animals, waste 1.1 BMB, biofuel 0.2 Soils* 7.9 Ocean 3.6 Total (Tg N2O-N/yr) 13.5 * post-forest clearing soils, soils under natural vegetation, fertilised agricultural fields HYMN year 2000 budget and uncertainties Anthropogenic source 6.8 +/- 0.5 Trend (+1 ppb/yr) 5.0 +/- 0.7 Net natural flux 10.8 +/- 3.1 Oceans 3.8 Soils nat. vegetation 7.0 Total (Tg N2O-N/yr) 17.6 +/- 3.2 Implied stratospheric sink 12.6 +/- 3.2