11.8.1.6 The need for an integrated approach

While the studies above adopt different methodological approaches, there is general consensus for all the world regions analyzed that near-term benefits from GHG reductions on human health, agriculture and natural ecosystems can be substantial, both in industrialized and developing countries. In addition, decarbonization strategies lead to reduced air pollution control costs. However, the benefits are highly dependent on the technologies and sectors chosen. In developing countries, many of the benefits could result from improvements to the efficiency of, or switching away from, traditional uses of coal and biomass. Such near-term secondary benefits of GHG control provide an opportunity for a true no-regrets GHG reduction policy in which substantial advantages accrue even if the impact of human-induced climate change itself turns out to be less than current projections indicate.

Climate mitigation policies, if developed independently from air pollution policies, will either constrain or reinforce air pollution policies, and vice-versa. The efficiency of a framework depends on the choice and design of the policy instruments, in particular on how well they are integrated. From an economic perspective, policies that may not be regarded as cost-effective from a climate change or an air pollution perspective alone may be found to be cost-effective if both aspects are considered. So piecemeal regulatory treatment of individual pollutants, rather than a comprehensive approach, could lead to stranded investments in equipment (for example, if new conventional air pollutant standards are put into place in advance of carbon dioxide controls at power plants) (Lempert et al., 2002).

On the basis of recent insights into atmospheric chemistry and health impacts, the literature has identified several concrete options for harvesting synergies between air pollution control and GHG mitigation, and has identified other options that induce undesired trade-offs.

The co-control of emissions – in other words controlling two or more distinct pollutants (or gases) that tend to emanate from a single source through a single set of technologies or policy measures – is a key element of any integrated approach. Air pollutants and GHGs are often emitted by the same sources and so changes in the activity levels of these sources affect both types of emissions. Technical emission control measures aiming at the reduction of one type of emissions from a particular source may reduce or increase the emissions of other substances.

In the energy sector, efficiency improvements and the increased use of natural gas can address both problems (resulting in synergy effects), while the desulphurization of flue gases reduces sulphur emissions but can – to a limited extent – increase carbon dioxide emissions (trade-offs). There are also trade-offs for NO_x control measures for vehicles and nitric acid plants, where increases in N₂O emissions are possible. Concerns have been expressed that measures that improve the local environmental performance of coal in electricity generation might result in a lock-in of coal technologies that will make it more difficult to mitigate CO₂ emissions (McDonald, 1999; Unruh, 2000).

In agriculture, some specific measures to abate ammonia emissions could enhance nitrous oxide and/or methane emissions, while other types of measures could reduce the latter. For Europe, Brink et al. (2001) have estimated that abating agricultural emissions of ammonia (NH₃) may cause releases of N₂O from this sector that are up to 15% higher than they would be without NH₃ control. There may be substantial differences in the observed effects between various countries, depending on the extent and type of NH₃ control options applied.