This WP will use a combination of transient (coupled ocean-atmosphere) and timeslice (fixed SST) experiments to consistently quantify forcings, feedbacks and climate response across different ESM simulations and different components of the Earth system This extends earlier work on carbon cycle feedbacks to other biogeochemical feedbacks; e.g. carbon dioxide, methane, ozone, sulphate, nitrate, dust, sea salt, as well as emissions of; wetland and permafrost methane, biomass burning (aerosol and ozone precursors), DMS and BVOCs. The three quantities needed to calculate the feedbacks are the radiative efficiencies (phi), interactions between atmospheric constituents (beta) and sensitivities to climate change (gamma), see Gregory et al 2009 for more details). WP Objectives include: (i) quantification of natural and anthropogenic ERF including biogeochemical interactions (phi and beta); (ii) quantification of sensitivities to climate (gamma); (iii) calculation of climate feedbacks from phi, beta and gamma; and (iv) quantification of climate response to aerosols and ozone. To facilitate future calculation of forcings and feedbacks diagnostics developed in the WP will be implemented in ESMValTool.