Climate change mitigation necessitates substantial alterations to patterns of worldwide economic activity, be that reduction in demand, switches to new technology or 'end-of-pipe' abatement of greenhouse gases. There are profound political, economic and ethical questions surrounding the governance of the means, rate and location of change. Within advanced capitalist economies and internationally through the auspices of the United Nations Framework Convention on Climate Change emissions trading systems have been introduced as part of the broader neoliberal attempts to 'correct market failure' through the definition of new property rights.This thesis investigates the development, constitution and consequences of institutions for the production, exchange and consumption of credits for emissions reductions. Such credits are financial instruments awarded to organisations for putative reductions in emissions from 'business as usual'. In consumption, credits are equated with a quantity of emissions released elsewhere. The 'Instituted Economic Process' framework (Randles and Harvey, 2002) is used to distinguish the various classes of agent involved in these exchanges and identify the economic and non-economic relationships that constitute these institutions. Inspired by the economic anthropology of Karl Polanyi, this approach asks how economic activity is organised and stabilised within society without presuming that there are universal economic laws of 'the market', that there are essential properties of commodities and agents, or that all economic transfers are conducted within markets.I argue that crediting is a socially contingent process of commodification of atmospheric pollution which is both ontologically and normatively problematic. Extant institutions are shown to be precarious by appealing to neutral techno-scientific justifications but remaining reliant on subjective judgement. However, they are sufficiently consistent and credible that they persist and expand. These findings are of interest to the academic communities of political economy and environmental and economic geography, climate change policy makers and the environmental movement more broadly.