The composition of short-lived, reactive species in the atmosphere both affects and is affected by climate. I will discuss model results examining composition-climate interactions for ozone, methane and aerosols. The results provide initial steps towards informing policy on the linked issues of air quality and climate change. These include identifying potential metrics for valuing emissions limitations and highlight sectors and regions where controls might be most effective in combined climate mitigation and air quality improvement. I will also discuss efforts to calculate net climate impacts of short-lived precursor emissions, as well as modeling of the relative global and regional impacts of the short-lived chemically and radiatively active species as compared with the WMGHGs in the past and future.