Protecting A Lesser Known Planetary Boundary: International Legal Responses to Atmospheric Aerosol Loading

Abstract

The global concentration of aerosol particles has more than doubled since pre-industrial times. Their harmful impacts on human health and the climate have justified the inclusion of ‘atmospheric aerosol loading’ as one of the nine planetary boundaries. The chapter maps the international legal landscape applicable to aerosol loading and identifies two categories of responses: one concentrating explicitly on limiting aerosol emissions, including by regulating air pollution, and the other indirectly targeting emissions by governing their sources, such as fossil fuel combustion and land-use changes. It is noteworthy that, in response to improved public awareness of air pollution, the international community has recently started to mobilize more adequately to protect this planetary boundary. However, it is arguably one of the more elusive planetary boundaries for policy-makers and lawyers, due to the complexity and remaining uncertainties surrounding scientific knowledge on aerosol loading. The planetary boundary is also difficult to apprehend because it concentrates only partially on the air pollution problem and proposes a global frame to respond to a primarily regional problem. A further hurdle lies in a lack of political appetite for an international, legally-binding, framework to govern aerosol loading. As a result, a complex international legal landscape has emerged, characterized by its fragmentation and reliance on non-treaty alternatives, that has, so far, been unable to provide an optimal and comprehensive response to protect the planetary boundary.

Keywords: atmospheric aerosol loading, planetary boundaries, air pollution, aerosols, black carbon, climate change