We estimate effects of voluntary and mandatory disclosure of carbon emissions on stock returns and volatility using a large global sample of publicly listed firms. We find that voluntary disclosure of scope 1 emissions by companies results in lower stock returns relative to non-disclosing companies. However, a cost of disclosing emissions is increased divestment by institutional investors. We also find that U.K. mandatory carbon disclosure rules for publicly traded companies resulted in lower stock-level uncertainty. The effect of these mandatory disclosure rules also spilled over into other markets, especially those with close geographic and economic proximity, and companies in the same industry.