Editing IPCC:AR6/WGIII/Chapter-2 (section)

==== 2.8.3.2 Selected Sectoral Climate Policy Instruments ====

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Many governments have implemented sector-specific policies, in addition to nationwide measures, to reduce GHG emissions ( ''high confidence'' ). Examples of sectoral climate policies include carbon taxes on transportation fuels, low-carbon fuel standards, and regulation of coal power generation.

The implementation of a carbon tax and value-added tax on gasoline and diesel in Sweden resulted in significant reductions of CO 2 emissions in the transportation sector ( [[#Shmelev--2018|Shmelev and Speck 2018]] ; [[#Andersson--2019|Andersson 2019]] ). An assessment of a variety of carbon tax schemes across various sectors in the EU shows a negative relationship between CO 2 emissions and a CO 2 tax ( [[#Hájek--2019|Hájek et al. 2019]] ). In British Columbia (Canada), the carbon tax resulted in a decrease in demand for gasoline and a reduction in total GHG emissions (not exclusive to the transportation sector) estimated to be between 5–15% ( [[#Murray--2015|Murray and Rivers 2015]] ; [[#Rivers--2015|Rivers and Schaufele 2015]] ). The Low Carbon Fuel Standard in California has contributed to reducing carbon emissions in the transportation sector by approximately 9.85–13.28% during 1997–2014 ( [[#Huseynov--2018|Huseynov and Palma 2018]] ).

The power sector typically accounts for a large portion of countries’ CO 2 emissions. Market-based regulation and government subsidies in China contributed to improving operational efficiency and reducing emissions ( [[#Zhao--2015|Zhao et al. 2015]] ). In addition, the implementation of ultra-low emission standards has also resulted in a significant reduction in emissions from China’s power plants ( [[#Tang--2019|Tang et al. 2019]] ). Mandatory climate and energy policies, including the California Global Warming Solutions Act, reduced CO 2 emissions by 2.7–25% of the average state-level annual emissions from the power sector over the period 1990–2014 in the USA. Mandatory GHG registry/reporting, electric decoupling and a public benefit fund have been effective in further decreasing power sector emissions in the USA ( [[#Martin--2017|Martin and Saikawa 2017]] ). In the UK electricity sector, a carbon price floor, combined with electricity market reform (competitive auctions for both firm capacity and renewable energy), displaced coal, whose share fell from 46% in 1995 to 7% in 2017, halving CO 2 emissions, while renewables grew from under 4% in 2008 to 22% by 2017 ( [[#Grubb--2018|Grubb and Newbery 2018]] ). See [[IPCC:Wg3:Chapter:Chapter-13|Chapter 13]] for more information.

An alternative approach to a carbon tax is an indirect emissions tax on fuels such as an excise tax, or on vehicles, based on the expected CO 2 intensity of new passenger vehicles. Vehicle purchase taxes can result in a reduction in GHG emissions through reducing the CO 2 emissions intensity of vehicles, while also discouraging new vehicle purchases ( [[#Aydin--2018|Aydin and Esen 2018]] ). For example, a vehicle tax policy in Norway resulted in a reduction of average CO 2 intensity per kilometre of 7.5 gCO 2 km –1 ( [[#Ciccone--2018|Ciccone 2018]] ; [[#Steinsland--2018|Steinsland et al. 2018]] ). Despite such evidence, studies of carbon pricing find that additional policies are often needed to stimulate sufficient emissions reductions in transportation ( ''medium confidence'' ) ( [[#Tvinnereim--2018|Tvinnereim and Mehling 2018]] ).

Electric vehicles (EVs) powered by clean electricity can reduce GHG emissions, and such policies are important for spurring adoption of such vehicles ( [[#Kumar--2020|Kumar and Alok 2020]] ; [[#Thiel--2020|Thiel et al. 2020]] ). The extent to which EV deployment can decrease emissions by replacing internal combustion engine-based vehicles depends on the generation mix of the electric grid ( [[#Abdul-Manan--2015|Abdul-Manan 2015]] ; [[#Nichols--2015|Nichols et al. 2015]] ; Canals [[#Casals--2016|Casals et al. 2016]] ; [[#Hofmann--2016|Hofmann et al. 2016]] ; [[#Choi--2018|Choi et al. 2018]] ; [[#Teixeira--2018|Teixeira and Sodré 2018]] ) although, even with current grids, EVs reduce emissions in almost all cases ( [[#Knobloch--2020|Knobloch et al. 2020]] ). Policy incentives for EV adoption can be an effective mechanism to increase EV sales ( [[#Langbroek--2016|Langbroek et al. 2016]] ) and may include discounts, purchase subsidies, regulations, and government leadership ( ''medium confidence'' ) ( [[#Bakker--2013|Bakker and Jacob Trip 2013]] ; [[#Silvia--2016|Silvia and Krause 2016]] ; [[#Teixeira--2018|Teixeira and Sodré 2018]] ; [[#Qiu--2019|Qiu et al. 2019]] ; [[#Santos--2020|Santos and Davies 2020]] ). The presence of charging infrastructure and publicly available charging increases the adoption rate of EVs ( [[#Vergis--2015|Vergis and Chen 2015]] ; [[#Javid--2019|Javid et al. 2019]] ). A comparison of EV adoption rates across 30 countries shows a positive correlation between charging stations and EV market share ( [[#Sierzchula--2014|Sierzchula et al. 2014]] ). A rollout of 80,000 DC fast chargers across the USA is estimated to have resulted in a 4% reduction in emissions compared to a baseline of no additional fast chargers ( [[#Levinson--2018|Levinson and West 2018]] ). More recently, bans on internal combustion engine vehicles have provided a much more direct approach to stimulating the adoption of EVs and its supporting infrastructure; however, the efficacy of such measures depends on enforcement ( [[#Plötz--2019|Plötz et al. 2019]] ).

Public transit can reduce vehicle travel and lower GHG emissions by reducing the number of trips taken by private vehicles and the length of those trips ( ''medium confidence'' ). Changes to the operation of public transportation systems (such as density of bus stops, distance from stops to households, duration and frequency of trip times, and lowering ridership costs) can result in a mode shift from private car trips to public transit trips ( [[#Cats--2017|Cats et al. 2017]] ; [[#Choi--2018|Choi 2018]] ; [[#Carroll--2019|Carroll et al. 2019]] ). These changes in the public transit system operation and network optimisation have been shown to have reduced GHG emissions in cases such as San Francisco, where the cost optimisation of the transit network was estimated to decrease emissions by a factor of three ( [[#Cheng--2018|Cheng et al. 2018]] ) and Barcelona, where the optimisation of the urban bus system was estimated to reduce GHG emissions by 50% ( [[#Griswold--2017|Griswold et al. 2017]] ). For every 1% increase in investment in transit services and transit-oriented design, there is an estimated 0.16% reduction in private vehicle kilometres travelled per capita ( [[#McIntosh--2014|McIntosh et al. 2014]] ).

Bike- and car-sharing programmes can reduce GHG emissions ( ''medium confidence'' ). Albeit a study of eight cities in the USA with larger bike share systems and higher ridership found that their potential to reduce total emissions is limited to &lt;0.1% of total GHG emissions from the transportation sectors of these cities ( [[#Kou--2020|Kou et al. 2020]] ). The emissions reductions effects of car-sharing programmes depends on the specifics of programmes: the mode shift from public transit to car-sharing services can outweigh the decreases in GHG emissions associated with a reduced number of cars on the road ( [[#Jung--2018|Jung and Koo 2018]] ), whereas car-sharing programmes with EV fleets may reduce GHG emissions ( [[#Luna--2020|Luna et al. 2020]] ).

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