Protecting the environment is now a major aspect of corporate social responsibility. However, voluntary carbon disclosure includes private information on future sustainability that external stakeholders cannot easily verify. Drawing on information asymmetry theory, we predict that companies with higher carbon information asymmetry between insiders and outsiders have a greater incentive to voluntarily engage an external party for the independent assurance of their greenhouse gas statements. Using data from the CDP, we test this hypothesis and find that our proxies for carbon information asymmetry (e.g., greenhouse gas emissions, energy structure) are significantly associated with the adoption of carbon assurance. Further analyses suggest that the probability of carbon assurance is enhanced when carbon disclosure is inadequate to diminish information asymmetry. Finally, our sample companies adopted carbon assurance in addition to financial auditing. This highlights the key point that resolving carbon information asymmetry requires carbon assurance, which cannot be substituted for by financial auditing.

现在，保护环境已成为企业社会责任的重要方面。但是，自愿碳公开包括有关外部利益相关者无法轻松验证的有关未来可持续性的私人信息。基于信息不对称理论，我们预测内部人和外部人之间碳信息不对称率较高的公司有更大的动机自愿聘请外部方来独立保证其温室气体声明。使用来自CDP的数据，我们检验了这一假设，发现我们对于碳信息不对称性（例如，温室气体排放，能源结构）的代理与采用碳保证显着相关。进一步的分析表明，当碳披露不足以减少信息不对称时，碳保证的可能性就会提高。最后，我们的样本公司在财务审计之外还采用了碳保证。这突出了解决碳信息不对称需要碳保证的关键点，而碳保证不能用财务审计来代替。