The Ethics of Geoengineering: Moral Considerability and the Convergence Hypothesis TOBY SVOBODA ABSTRACT Although it could avoid some harmful effects of climate change, sulphate aerosol geoengineering (SAG), or injecting sulphate aerosols into the stratosphere in order to reflect incoming solar radiation, threatens substantial harm to humans and non-humans. I argue that SAG is prima facie ethically problematic from anthropocentric, animal liberationist, and biocentric perspectives.This might be taken to suggest that ethical evaluations of SAG can rely on Bryan Norton’s convergence hypothesis, which predicts that anthropocentrists and non- anthropocentrists will agree to implement the same or similar environmental policies. However, there are potential scenarios in which anthropocentrists and non-anthropocentrists would seem to diverge on whether a particular SAG policy ought to be implemented.This suggests that the convergence hypothesis should not be relied on in ethical evaluation of SAG. Instead, ethicists should consider the merits and deficiencies of both non-anthropocentric perspectives and the ethical evaluations of SAG such perspectives afford. Introduction Geoengineering, or the intentional manipulation of the Earth’s environment on a large scale, 1 could avoid some of the potentially harmful effects of climate change, such as increases in temperature and sea level. 2 However, geoengineering also threatens sub- stantial harm of its own to both human beings 3 and non-human entities. Given this risk of harm, geoengineering strategies require ethical evaluation. In evaluating geoengineer- ing strategies, one might rely on Bryan Norton’s convergence hypothesis, according to which anthropocentrists and non-anthropocentrists, despite their divergent theoretical commitments, will agree to implement the same or similar environmental policies. 4 However, while the convergence hypothesis has many virtues and is worth considering in the context of geoengineering, I argue that it is plausible to expect anthropocentric and non-anthropocentric evaluations of some geoengineering policies to diverge in certain realistic scenarios. Accordingly, the question of which (if any) non-humans deserve moral consideration is relevant for ethical evaluations of geoengineering strategies, given that some such strategy might be morally acceptable by anthropocentric lights but not by non-anthropocentric lights. This article examines geoengineering in the form of injecting sulphate aerosols into the Earth’s stratosphere. In the first section, I sketch the science of sulphate aerosol geoengineering (SAG) and briefly discuss how SAG could avert some of the effects of anthropogenic climate change. In the second section, I consider some of the specific impacts and risks of SAG, including its potential to harm human beings and non-human Journal of Applied Philosophy,Vol. 29, No. 3, 2012 doi: 10.1111/j.1468-5930.2012.00568.x © Society for Applied Philosophy, 2012, Blackwell Publishing, 9600 Garsington Road, Oxford, OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA.