The past five years have seen explosive growth in “corporate green bonds” issued to finance climate-friendly projects. While investors bought just $3 billion of these bonds in 2013, they scooped up $49 billion worth in 2017, bringing the total sold since 2013 to $113 billion at an average of $308 million per offering. A wide range of companies including Apple, Unilever, and Bank of America have issued green bonds in recent years, and the trend is likely to continue. Despite this boom, little is known about the impact of these bonds. Have they delivered positive environmental results? Do they contribute to the issuing companies’ financial performance? The answer to both questions is a resounding yes.