The Earth’s changing climate is affecting human health and the environment in many ways. Across the United States (U.S.), temperatures are rising, snow and rainfall patterns are shifting, and extreme climate events are becoming more common. Scientists are confident that many of the observed changes in the climate are caused by the increase in greenhouse gases (GHGs) in the atmosphere. As GHG emissions from human activities increase, many climate change impacts are expected to increase in both magnitude and frequency over the coming decades, with risks to human health, the economy, and the environment. Actions can be taken now to reduce GHG emissions and avoid many of the adverse impacts of climate change. Quantifying the benefits of reducing GHG emissions (i.e., how GHG mitigation reduces or avoids impacts) requires comparing projections of climate change impacts and damages in a future with policy actions and a future without policy actions. Looking across a large number of sectors, this report communicates estimates of these benefits to the U.S. associated with global action on climate change.