Editing IPCC:AR6/WGIII/Chapter-10 (section)

=== 10.6.2 Short-lived Climate Forcers and Shipping ===

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Like aviation, shipping is also a source of emissions of SLCFs as described in [[#10.5|Section 10.5]] , including nitrogen oxides (NO x ), sulphur oxides (SO x , such as SO 2 and SO 4 ), carbon monoxide (CO), black carbon, and non-methane volatile organic compounds (NMVOCs) ( [[#Szopa--2021|Szopa et al. 2021]] ). Though SLCF have a shorter lifetime than the associated CO 2 emissions, these short-lived forcers can have both a cooling effect (e.g., SO x ) or a warming effect (e.g., ozone from NO x ). The cooling from the SLCF from a pulse emission will decay rapidly and diminish after a couple of decades, while the warming from the long-lived substances lasts for centuries ( [[#Szopa--2021|Szopa et al. 2021]] ).

Emissions of SLCF from shipping not only affect the climate, but also the environment, air quality, and human health. Maritime transport has been shown to be a major contributor to coastal air quality degradation ( [[#Zhao--2013|Zhao et al. 2013]] ; [[#Jalkanen--2014|Jalkanen et al. 2014]] ; [[#Viana--2014|Viana et al. 2014]] ; [[#Goldsworthy--2015|Goldsworthy and Goldsworthy 2015]] ; [[#Goldsworthy--2017|Goldsworthy 2017]] ). Sulphur emissions may contribute towards acidification of the ocean ( [[#Hassellöv--2013|Hassellöv et al. 2013]] ). Furthermore, increases in sulphur deposition on the oceans have also been shown to increase the flux of CO 2 from the oceans to the atmosphere ( [[#Hassellöv--2013|Hassellöv et al. 2013]] ). To address the risks of SO x emissions from shipping, there is now a cap on the on the sulphur content permissible in marine fuels ( [[#IMO--2013|IMO 2013]] ). There is also significant uncertainty about the impacts of pollutants emitted from ships on the marine environment ( [[#Blasco--2014|Blasco et al. 2014]] ).

Pollution control is implemented to varying degrees in the modelling of the SSP scenarios ( [[#Rao--2017|Rao et al. 2017]] ); for example, SSPs 1 and 5 assume that increasing concern for health and the environment result in more stringent air pollution policies than today ( [[#Szopa--2021|Szopa et al. 2021]] ). There is a downward trend in SO x and NO x emissions from shipping in all the SSPs, in compliance with regulations. The SLCF emissions reduction efforts, within the maritime sector, are also contributing towards achieving the UN SDGs. In essence, while long-lived GHGs are important for long-term mitigation targets, accounting for short-lived climate forcers is important both for current and near-term forcing levels as well as broader air pollution and SDG implications.

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