Meridional gradients in CO2 forcing are known to drive increases in poleward heat transport (Huang and Zhang 2014, Huang et al. 2017). However, the climate factors which control these meridional forcing gradients are not well understood. Building upon the work of Wilson (2012), we build a first-principles, analytical model for CO2 forcing which requires as input only the temperatures at the surface and roughly 30 hPa, as well as column relative humidity. This model quantitatively captures global variations in clear-sky CO2 forcing, and shows that the meridional forcing gradient is directly attributable to the meridional surface temperature gradient.