If the goals of the Paris Agreement are to be met, the importance of accelerating emissions reductions grows with each passing year. It is also important, then, to better understand the role of climate policy tools in emissions abatement. Emissions pricing is one such tool, be it in the form of a carbon tax or an emissions trading system. This is but one example of how the design of an emissions pricing system can vary, and understanding the relationship between a system’s policy design and its emissions reductions is a key aspect of understanding its effectiveness. To this end, I perform a structured literature review of academic journal articles studying the ex post emissions reduction effects of emissions pricing systems, analyzing the results from 44 articles. I find that on average, emissions pricing systems have reduced emissions by 7.7 per cent. Some systems have resulted in large emissions reductions with a relatively modest price per tonne of CO2e. Many researchers note that exemptions in systems have hindered their effectiveness. Overall results indicate that the relationship between a system’s design — in terms of price level and emissions coverage — and its emissions reducing effect is complex, and there are various confounding factors for any given jurisdiction that must be considered.