We study stock market reactions to corporate announcements of emissions reduction targets. Using generative AI, we identify 2,417 announcements and document three findings. First, target announcements are associated with negative stock price reactions. Second, firms with more credible disclosures receive more negative reactions. Third, firms with more negative market reactions subsequently reduce their emissions more. We identify two reasons firms set targets and follow through despite negative market reactions: (i) benefits are realized later when climate regulation materializes; and (ii) ESG-linked pay incentivizes target announcement and subsequent decarbonization. Our findings shed light on how market values voluntary climate commitments.