Exxon Mobil Corp. has agreed to disclose how the regulation of carbon emissions could affect the value of its oil and gas holdings, a sign that America's biggest energy company is stepping up efforts to address shareholders' environmental concerns.

The oil giant will publish a report later this month explaining how it weighs the risks that regulations could make it prohibitively expensive to tap oil and gas, according to Arjuna Capital, an investment management firm focused on social responsibility that submitted a shareholder...