Climate change is such a large and sprawling problem — there are so many forces involved, so many decision makers at so many levels — that solving it can seem hopelessly complex. There are so many options available to policymakers, each with their own fierce constituencies. Where to begin? Which clean-energy policies actually work? That is the question Hal Harvey, long-time energy analyst and CEO of the energy policy firm Energy Innovation, set out to answer with a new tool. The tool is the Energy Policy Simulator, which allows anyone to choose a package of energy policies and immediately see the impact on carbon emissions and other pollutants. (It’s like a video game for energy nerds.) It’s based on a model that attempts to replicate the physical economy, with detailed information about real-world assets. Using that tool, Harvey and his team narrowed in on the policies that work, the places they work best, and the best way to design them. Their conclusions are summarized in a new book, Designing Climate Solutions: A Policy Guide for Low-Carbon Energy. It’s a compact but detailed how-to guide for developing energy policies that have real impact…the results are oddly heartening, or at least clarifying.