The economic appraisal of greenhouse gases (GHG) emissions is complex. The shadow price of carbon (SPC) is derived from the best estimate of the present value of damages associated with a tonne of GHG emission in carbon dioxide equivalents (CO2 eq). The SPC rises with time, reflecting the increasing marginal damage of a tonne of GHG when added to a growing stock of atmospheric GHGs. There are many possible technical mitigation options for livestock systems, one of which includes harnessing selection tools. The study of Stott et al. (2005) describes how relative economic values (REVs) are calculated for traits included in the UK dairy profit index (£PLI) using dynamic programming tools to model a whole farm system. The REV for each trait is calculated by examining the consequence of a unit change in a trait of interest on net farm revenue, while keeping all other traits in the index fixed. The SPC provides a useful mechanism of considering the costs of GHG emissions in an economic index framework, such as £PLI. This study outlines methods for incorporating the environmental value of emissions mitigation into breeding goals.