Editing IPCC:AR6/WGI/Chapter-6 (section)

===== 6.6.2.3.2 Shipping =====

<div id="h4-2-siblings" class="h4-siblings"></div>

Quantifying the effects of shipping on climate is particularly challenging because (i) the sulphate cooling impact is dominated by aerosol–cloud interactions and (ii) ship emissions contain NO <sub>x</sub> , SO <sub>x</sub> and BC, which lead to mixed particles. Previous estimates of the sulphate radiative effects from present-day shipping span the range –47 to –8 mW m <sup>–2</sup> (direct radiative effect) and –600 to –38 mW m <sup>–2</sup> (indirect radiative effects) (Lauer et al. , 2007; Balkanski et al. , 2010; Eyring et al. , 2010; Lund et al. , 2012) . [[#Partanen--2013|Partanen et al. (2013)]] reported a global mean ERF for year-2010 shipping aerosol emissions of –390 mW m <sup>–2</sup> . The temperature change has been shown to be highly sensitive to the choice of aerosol–cloud parametrization ( [[#Lund--2012|Lund et al., 2012]] ). One year of global present-day shipping emissions, not considering the impact of recent low sulphur fuel regulation ( [[#IMO--2016|IMO, 2016]] ), are estimated to cause net cooling in the near term (–0.0024°C ± 0.0025°C) and slight warming (+0.00033°C ± 0.00015°C) on a 100-year horizon ( [[#Lund--2020|Lund et al., 2020]] ).

Shipping is also of importance for air pollution in coastal areas along the major trade routes, especially in Europe and Asia (Corbett et al. , 2007; H. Liu et al. , 2016, Figure 6.17; Jonson et al. , 2020). Jonson et al. (2020) estimated that shipping is responsible for 10% or more of the controllable PM <sub>2.5</sub> concentrations and depositions of oxidised nitrogen and sulphur for many coastal countries. Widespread introduction of low-sulphur fuels in shipping from 2020 ( [[#IMO--2016|IMO, 2016]] ) will lead to improved air quality and reduction in premature mortality and morbidity ( [[#Sofiev--2018|Sofiev et al., 2018]] ).

In summary, a year’s worth of present-day global shipping emissions (i.e., without the implementation of the 2020 clean fuel standards) cause a net global cooling (–0.0024 ± 0.0025°C) on 10–20 year time horizons ( ''high confidence'' ) but its magnitude is of ''low confidence'' .

<div id="6.6.2.3.3" class="h4-container"></div>

<span id="land-transportation"></span>