In this chapter we discuss the underlying uncertainties in the hypotheses that motivate emission reduction measures and physical and monetary impacts of these. We have discussed the validity of four key claims using the approach described in Chapter 2.3.
1. Human activity increases air pollution concentrations in Nordic countries
Claim #1 can be assessed using observational and modelling studies, which provides a good possibility for solid validity. Measurements show that air quality is worse in close proximity to human activities such as heavy traffic or industries. Chemical/optical analysis of pollutants gathered from ambient air indicate their origin as anthropogenic rather than natural (examples of natural would include dust, sea salt etc.). Observational and modelling studies agree that both long-range transported and locally produced emissions from human activities contribute to concentrations in Nordic countries.
2. Increased air pollution concentrations cause health problems in Nordic countries
Increased concentrations of air pollution, especially fine particulate matter, NOX and ozone, have been connected to various health hazards in numerous population and toxicological studies. In the scientific literature, there is agreement regarding the claim that increased concentrations cause health problems in Nordic countries. However, there is higher uncertainty or at least variability regarding the effects on human health when concentration levels in ambient air are relatively low.
3. Emissions of short-lived climate forcers from Nordic countries affect climate change
The short-lived climate forcers considered in this report are estimated to impact the climate by altering the atmosphere’s radiative forcing. This impact can be either warming (most notably for BC) or cooling (most notably for SO2 and OC). The impacts can be measured in labs (Bond et al. 2013). Larger scale assessments are modelled, and there are no “source apportionment” methods for determining what has caused the rise in measured temperatures in ambient air.
In general, the literature suggests variance on the estimated climate impact of air pollutants, depending on the model being used. The studies also always include uncertainties due to limitations of the models and understanding of the physical processes involved. The issue is complex, because the impact of a given emission is estimated to vary greatly depending on the location and season, which affect the albedo and meteorology in the area of impact (Borgar Aamaas et al. 2016; Sand et al. 2020; Räisänen et al. 2022). Another problem in determining impacts of local emissions is a low signal-to-noise ratio in model runs. This means that for a small amount of emissions, such as those coming from Europe for example, a strong upward scaling is typically needed to see impacts in the models as in Sand et al. (2020).
4. Increased/decreased air pollution concentrations cause economic losses/gains in Nordic countries
It is clear from numerous health economic assessment studies that the health problems lead to economic losses of some kind. Episodes of poor air quality have been observed to increase mortality and hospital admissions. However, a purely utilitarian and time ignorant economic assessment (abandoned in environmental impact assessments) can show that health problems such as premature death can give economic benefits through reduced health care costs and payment of pensions (Heinzerling and Ackerman 2002). This is one of the reasons why willingness-to-pay studies are used to estimate the economic value of health effects. There is however no scientific consensus on which monetary metric or value to use in analysis, so there is a variance in the health cost estimates. In addition to health hazards, air pollution has been shown to negatively impact materials, crop production and the natural environment. However, these costs are typically estimated to be notably lower than health damage costs. Finally, the literature does not suggest any non-linearities, so improved air quality will provide benefits. Whether the benefits are larger than the costs of course will depend on the costs of the measures used to improve air quality. The overall assessment from the discussion on air pollution is found in Table 4.