The legal requirements governing State responsibility for transboundary pollution are now well settled at international law. However, the limited number of cases involving transboundary pollution that have been decided by international courts and tribunals leaves open many questions concerning the practical application of State responsibility doctrines in this context. This chapter unpacks the elements of a State responsibility claim for transboundary pollution, focusing on those elements that pose the most complex issues in practice. These include questions concerning how to attribute the polluting actions of private entities to States, the content of States’ obligation to act with ‘due diligence’ in the prevention of transboundary harm, and methodologies for proving the causation of injury through transboundary pollution. The chapter illustrates these questions by drawing on the example of transboundary air pollution through the emission of greenhouse gases contributing to climate change.

This chapter considers how international environmental law applies to the special situation of climate disaster. It examines efforts to adapt international environmental rules largely developed to respond to “manmade” disasters to hybrid climate disasters that involve both natural and human-sourced elements. It also discusses the scope for international environmental law tools and principles, such as precaution, EIA and participation, to be employed in climate disaster risk management. The final section explores challenges presented by efforts to forge better linkages between disaster management and environmental communities and institutions, with the aim of fostering more integrated approaches for dealing with climate disaster.

Questions regarding the assessment of scientific evidence, and the legal standards to be applied, have preoccupied international adjudicators across a wide array of forums considering environmental disputes, most notably the WTO in disputes under the Sanitary and Phytosanitary (SPS) Measures Agreement. Investor-state arbitrations over environment-related regulatory measures often raise similar questions about the appropriate use of science as have been seen in the WTO SPS case law. As investor-state arbitrations gather pace in the environmental field, we can expect questions over the role of science to become more prominent, as they have in other international dispute settlement fields. This chapter takes stock of scholarly discussion and existing practice regarding the use of science in environment-related investor-state arbitrations. Consideration of emerging practice in international investment law in the context of approaches taken in other areas of international dispute settlement provides a basis for identifying likely future challenges and evaluating proposed approaches.