Does the location of aircraft nitrogen oxide emissions affect their climate impact?

We present results from 112 one-year global chemistry-transport model integrations: a base case, then variants with extra aircraft nitrogen oxide (NOx) emissions added to specific regions in the first month (July). The NOx stimulates ozone (O-3) production and methane (CH4) destruction. Responses vary spatially: low background NOx regions are most sensitive. Integrated (100-year time horizon) radiative forcings (IRF) are calculated. Net (O-3 + CH4) IRFs for July aviation NOx are generally negative: the global average, weighted by emissions, is -1.9 mWm(-2) yr (TgNO(2))(-1). The positive IRF associated with the short-term O-3 increase (4.1 mWm(-2) yr (TgNO(2))(-1)) is overwhelmed by the effects of the long-term CH4 decrease. Aircraft NOx net IRFs are spatially variable, with July values over the remote Pacific approximately balancing the IRF associated with aviation CO2 emissions (28 mWm(-2) yr (TgNO(2))(-1)). The overall climate impact of global aviation is often represented by a simple multiplier for CO2 emissions. These results show that this is inappropriate. Citation: Stevenson, D. S., and R. G. Derwent (2009), Does the location of aircraft nitrogen oxide emissions affect their climate impact?, Geophys. Res. Lett., 36, L17810, doi: 10.1029/2009GL039422.