  A high degree of consensus exists in the climate sciences over the role that
human interference with the atmosphere is playing in changing the climate.
Following the Paris Agreement, a similar consensus exists in the policy
community over the urgency of policy solutions to the climate problem. The
context for climate policy is thus moving from agenda setting, which has now
been mostly established, to impact assessment, in which we identify policy
pathways to implement the Paris Agreement. Most integrated assessment models
currently used to address the economic and technical feasibility of avoiding
climate change are based on engineering perspectives with a normative systems
optimisation philosophy, suitable for agenda setting, but unsuitable to assess
the socio-economic impacts of a realistic baskets of climate policies. Here, we
introduce a fully descriptive, simulation-based integrated assessment model
designed specifically to assess policies, formed by the combination of (1) a
highly disaggregated macro-econometric simulation of the global economy based
on time series regressions (E3ME), (2) a family of bottom-up evolutionary
simulations of technology diffusion based on cross-sectional discrete choice
models (FTT), and (3) a carbon cycle and atmosphere circulation model of
intermediate complexity (GENIE-1). We use this combined model to create a
detailed global and sectoral policy map and scenario that sets the economy on a
pathway that achieves the goals of the Paris Agreement with >66% probability of
not exceeding 2$^\circ$C of global warming. We propose a blueprint for a new
role for integrated assessment models in this upcoming policy assessment
context.
