Black carbon reduction

Given the large scope of possible mitigation strategies, there is no clear answer for this, although most techniques are already readily available. There is a need for increased BC emission data and observation to design adequate policies. Kang et al., (2020), for instance, note large discrepancies between studies on BC concentrations, depending on measurement methods and models used. Moreover, it is not clear how effective BC mitigation would be as a measure to cool global and Arctic temperatures due to the many indirect effects of such mitigation (Kühn et al., 2020), and whether mitigation strategies could result in a net heating effect. For example, reducing sulfate particle emissions, which until have now had a cooling effect on temperatures, may have the opposite effect (Takemure and Suzuki, 2019; von Salzen et al., 2022).

The difficulty of scalability depends on the strategy and the source of BC. Although BC mitigation in the Arctic is shown to have significant potential (Aakre et al., 2017; Kühn et al., 2020), most BC in the region is from sources outside of the region (Browse et al., 2013; Khan and Kulovesi, 2018), necessitating international collaboration. Rypdal et al. (2009) argue that the most effective BC mitigation strategies would focus on Asia, as reductions in this region are relatively cheaper to acheive, and because a large portion of global BC emissions originate from Asia. 

Some of the technologies need to be developed further, but most mitigation strategies would be relatively quick to deploy, if adequate policies were implemented. Morevoer, BC mitigation strategies would be able to achieve effects on a relatively short timescale (Kühn et al., 2020).

Given the increased albedo reducing effect of BC on snowy and icy surfaces, the reduction of such particles would be of prime importance for the Arctic. There are, however, still significant uncertainties when ‘quantifying the role of BC in cryospheric melting' (Kang et al. 2020). Apart from the previously mentioned net warming effects that could come with changes in anthropogenic emissions, the role of BC on ice melt could, in some contexts, be relatively insignificant compared to other albedo-reducing particles such as dust or organic matter. Kaspari et al. (2020), for example, find that at present the effect of dust far outweighs that of BC when it comes to albedo effects on the North American South Cascade Glacier.

There are already numerous actions taken by states to address carbon, including the Arctic Council's “Enhanced Black Carbon and Methane Emissions Reductions: An Arctic Council Framework for Action”. Local mitigation strategies could also play an important role in this. Makarovaа et al. (2021), for example, showed that a mix of policies could reduce BC emissions in Murmansk by 65.5%. Aakre et al. (2017) write that major BC reductions in the Arctic can be made by specific groups of Arctic countries, and that Russia is of crucial importance for the Arctic region. Kühn et al. (2020) equally argue that Arctic states can significantly reduce regional BC concentrations by themselves.

Much attention in the Arctic has gone to shipping regulation, as 5 to 25% of air pollution in the region is shipping-related (Aliabadi et al. 2015). Comer et al. (2017) note that ‘[r]oughly two-thirds of the BC emissions (e.g.,193 tons) made in 2015 over the Arctic could be attributed to ships.’ Browse et al. (2013), however, highlight that shipping regulations in isolation might only be effective locally, such as in Greenland, where 10 to 15% of BC is attributable to shipping. They emphasize that major reductions would have to come through international regulations, as most of the BC in the Arctic is emitted from sources outside of the region. This international focus is also advocated by Khan and Kulovesi (2018), who also argue for ‘global engagement’.

According to a literature review by Kang et al. (2020), the globally averaged direct and indirect radiative forcing effects of BC are estimated to be up to 1.2 W m−2 and second only to those of CO2. However, due to the complexity of the indirect temperature effects of BC, such as cloud formation, assessing the effectiveness of mitigation efforts would be complicated, especially when compared to the mitigation of other aerosols such as methane (Smith et al., 2020). The ultimate net effects of mitigation, therefore, would likely be far smaller than assumed when only direct effects were taken into consideration (Kühn et al., 2020). Mitigation of BC would likely also impact the atmospheric presence of other aerosols such as sulfate (IPCC AR6 W3), which have had a net cooling effect on the climate (Takemure and Suzuki, 2019; von Salzen et al., 2022). Furthermore, Harmsen et al. (2020) write that 'the effect of BC mitigation on global mean temperature is found to be modest at best (with a maximum short-term GMT decrease of 0.02 °C in 2030) and could even lead to warming (with a maximum increase of 0.05 °C in case of a health-focused strategy, where all aerosols are strongly reduced).'

Costs and benefits depend highly on the chosen measure. Furthermore, different measures would be paid for by different groups. Legislation of shipping fuels, for example, would likely incur costs for commercial companies, while the alteration of combustion systems in public facilities would require public funds.

BC reduction would likely also entail reduction of other pollutants (IPCC AR6 WG3). This is generally beneficial, although the removal of certain other chemical particles like sulfite might ultimately also have a net warming effect, which could be detrimental to the environment (von Salzen et al., 2022).

Apart from the climate effects of BC mitigation, a reduction of black carbon particles in the air would also lead to significant health benefits (Shindell et al. 2012; Messner, 2020; IPCC AR6 WG3). Harmsen et al. (2020) even write that stringent action could potentially avoid or have avoided as many as 4 to 12 million deaths between 2015 and 2030. Kühn et al. (2020) argue that a successful BC mitigation in ‘all Arctic Council member and observer States could reduce the annual global number of premature deaths by 329,000 by the year 2030, which amounts to 9 % of the total global premature deaths due to particulate matter.'

There are several attempts to include such measures into Arctic and Northern governance, especially around shipping fuel (e.g., the Arctic-Council’s adaptation in 2015 of the “Enhanced Black Carbon and Methane Emissions Reductions: An Arctic Council Framework for Action”). Kühn et al. (2020) note that they believe the probability that such reductions will be implemented is relatively high, as organizations such as the Arctic Council have already done a lot of work on it, and member states have an active interest in its success.

There is significant interest into BC mitigation, especially when it comes to legislation of shipping fuels and the effects of forest fires. There have also been major global strategies from UNEP, and specific Arctic-focussed projects, including the EU-funded project "Arctic Black Carbon impacting on Climate and Air Pollution (ABC-iCAP" )abc-icap.amap.no), and the Arctic Council's “Enhanced Black Carbon and Methane Emissions Reductions: An Arctic Council Framework for Action” (Ginzburg, 2018).