Human activities around the world are producing increasingly large quantities of greenhouse gases (GHGs), the most abundant of which is carbon dioxide (CO2). In recent years, concerns about the effects those emissions might have on the climate have prompted Congress, federal regulators, and others to consider policies to reduce them. This book examines the unintended effects on the competitiveness of U.S firms of an economy wide policy, such as a carbon tax or a cap-and-trade program that would reduce emissions by imposing a price on them. The book also assesses the use of border adjustments, such as import tariffs and export subsidies, and transition assistance to mitigate those unintended effects.