Climate-economy models aiming at quantifying the costs and effects of climate change impacts and policies have become important tools for climate policy decision making. These models reproduce energy and emission scenarios over time and can inform us about the costs of achieving a given stabilization target or the optimal policy path. Modeling results are quite heterogeneous and subject to a significant degree of uncertainty. Although there are several important dimensions along which models differ, this chapter focuses on a key component of climate change economics and policy, namely technical change.