In this bonus episode of Climate Rising, we share an episode from Harvard Business School’s Cold Call podcast, featuring HBS professor Mike Toffel and Duncan van Bergen, Co-Founder of Calyx Global. The discussion focuses on Mike’s recent HBS case study, Calyx Global: Rating Carbon Credits, which explores how the company is helping improve transparency and credibility in the voluntary carbon market. Mike and Duncan join host Brian Kenny to unpack how Calyx Global evaluates carbon credit quality, how the company maintains independence in a space vulnerable to conflicts of interest, and how data and technology—from satellite sensing to AI—are transforming how carbon credits are verified and rated. The conversation also highlights key themes in the voluntary carbon market, including the tension between financial models and credibility, the challenges of measuring impact, and the broader implications for corporate climate action.