A global perspective on air pollution
The recent global implementation of the GAINS (Greenhouse gas – Air pollution Interactions and Synergies) model now enables a fresh perspective on air pollution trends in different world regions. Conventional long-term projections of global air pollutant emissions in the literature that are used for climate simulations ignore the pivotal role of policy interventions, assuming that there will be an automatic decline in emission intensities following the assumed increase in per capita income. As a result, the available scenarios suggest that air pollution will be a diminishing problem, as air pollutant emissions would sharply decline simply as a result of increasing economic wealth. However, while such an inverse relationship between pollution and wealth (the environmental Kuznetsk hypothesis) has been demonstrated in the past for urban sulfur dioxide (SO2) emissions, such behavior is less obvious for other pollutants; turning points, if they can be observed, occur at different income levels. Furthermore, as experience shows, bending trends downwards has required strong policy interventions in response to public pressure and incorporating scientific findings.
In 2012 the GAINS model was used to construct a range of air pollution scenarios up to 2050 for alternative assumptions with respect to dedicated policy interventions on emission controls. For instance, future emissions of nitrogen oxides (NOx) could vary by up to a factor of four, between a scenario that assumes no further air pollution controls and a case in which all emission control measures that are commercially available today are fully implemented. Governance, including compliance with already agreed emission control legislation, emerges as a key determinant of future environmental quality. Thus, policy interventions will be critical for future air pollution levels, and as a result, there is ample scope for win-win emission control strategies that also reduce greenhouse gas emissions.
These findings have been published in several papers (e.g., Klimont et al., 2013), and gridded emission fields of 10 short-lived pollutants for alternative policy scenarios have been made available to the scientific community as input for climate-chemistry models.
