We introduce the decomposition of carbon emissions into an expected and an unexpected component and analyze the association between these components and firm value. The expected component captures a firm's average carbon emissions inherent to its business model and operating environment. The unexpected component, meaning the firm-specific deviation from expected carbon emissions, reflects the management's effort and ability to implement carbon management and actively influence carbon emissions. For a sample of US firms operating in carbon-intensive industries, we estimate the expected component using a regression of carbon emissions on firm characteristics and industry. The residual of this regression represents the unexpected component. The results reveal that, on average, investors attach value to both components. While investors consider the expected component to be relevant regardless of assurance, they consider the unexpected component to be more relevant in the presence of assurance. The assurance alleviates credibility concerns about the information content of the unexpected component. Additionally, we confirm the nomological validity of our measure of the unexpected component, as it is negatively related to indicators of better carbon management systems.