Variation of radiative forcings and global warming potentials from regional aviation NO x emissions

Abstract

h i g h l i g h t sThe effects from hemispherical/regional aircraft NO x emissions are explored using 3D CTM, MOZART-3. The climate metrics values decrease with increasing regional aircraft NO x emission rates, except for Southeast Asia. Regional applications of an equal mass and a relative mass of aircraft NO x emission result in different regional dependencies. The greatest net NO x radiative forcing is observed for remote northern oceanic regions. a b s t r a c tThe response to hemispherical and regional aircraft NO x emissions is explored by using two climate metrics: radiative forcing (RF) and Global Warming Potential (GWP). The global chemistry transport model, MOZART-3 CTM, is applied in this study for a series of incremental aircraft NO x emission integrations to different regions. It was found that the sensitivity of chemical responses per unit emission rate from regional aircraft NO x emissions varies with size of aircraft NO x emission rate and that climate metric values decrease with increasing aircraft NO x emission rates, except for Southeast Asia. Previous work has recognized that aircraft NO x GWPs may vary regionally. However, the way in which these regional GWPs are calculated are critical. Previous studies have added a fixed amount of NO x to different regions. This approach can heavily bias the results of a regional GWP because of the well-established sensitivity of O 3 production to background NO x whereby the Ozone Production Efficiency (OPE) is greater at small background NO x . Thus, even a small addition of NO x in a clean-air area can produce a large O 3 response. Using this 'fixed addition' method of 0.035 Tg(N) yr À1 , results in the greatest effect observed for North Atlantic and Brazil,~10.0 mW m À2 /Tg(N) yr À1 . An alternative 'proportional approach' is also taken that preserves the subtle balance of local NO x eO 3 eCH 4 systems with the existing emission patterns of aircraft and background NO x , whereby a proportional amount of aircraft NO x , 5% (N) yr À1 , is added to each region in order to determine the response. This results in the greatest effect observed for North Pacific that with its net NO x RF of 23.7 mW m À2 /Tg(N) yr À1 is in contrast with the 'fixed addition' method. For determining regional NO x GWPs, it is argued that the 'proportional' approach gives more representative results. However, a constraint of both approaches is that the regional GWP determined is dependent on the relative global emission pattern, so if that changes in the future, the regional NO x GWP will change.

The contribution of aviation NOx emissions to climate change: are we ignoring methodological flaws?

“…polluted cities) and [4] (column 1) and adding additional processes such as PMO and SWV (column 2). PMO is taken with a mean factor of 40% of the methane RF, based on different estimates (29% [21], 58% [22], 23% [17], 47% [16] and 42% [23]); and SWV with a factor of 15% [18,24]. The revised formula for calculating the methane RF (column 3) can be found in Etminan et al (2016) [19]; original in Myhre et al (1998) [25] (see also supplementary material for the calculation).…”

Marginal climate and air quality costs of aviation emissions

“…Air quality impacts were calculated for both near ground emissions (Unal et . Climate impact studies typically estimated the total speciated radiative forcing from one year of aviation emissions (Penner et al 1999, Sausen et al 2005, Lee et al 2009, Brasseur et al 2016, or focused on studying one climate forcer, including specifically contrails (Burkhardt and Kärcher 2011, Chen and Gettelman 2013, Schumann and Graf 2013, Chen and Gettelman 2016, Bock and Burkhardt 2019 and aviation NO x emissions (Wild et al 2001, Stevenson et al 2004, Köhler et al 2008, Hoor et al 2009, Holmes et al 2011, Søvde et al 2014, Skowron et al 2015. In addition, Lund et al (2017a) presented regionalized aviation impact climate metrics.…”

Climate benefits of proposed carbon dioxide mitigation strategies for international shipping and aviation

“…Planned and proposed mitigation policies in each sector that specifically target CO 2 emissions have the potential to significantly reduce this climate impact. However, policies that target the mitigation of non-CO 2 climate pollutants, often through air quality management, result in emissions reductions that may not always avoid future warming (Kapadia et al, 2016;Sofiev et al, 2018;Yim et al, 2015). For example, if the emissions of all shipping-produced cooling agents (sulfur dioxide, nitrogen oxides, and organic carbon) were immediately halted and the shipping sector successfully decarbonized by mid-century, the sector would increase the world's temperatures through the end of the century (Fuglestvedt et al, 2009).…”