This paper investigates factors responsible for changes in carbon dioxide emission due to gas flaring in the upstream sector of the Nigerian oil and gas industry over the period 1965–2009. It also evaluates how this rate of change affects the extent of disclosure of gas flaring information in the Annual Statistical Bulletin (ASB) published by the Nigerian National Petroleum Corporation (NNPC). We find that size and the environmental philosophy in the industry have very strong positive impact on gas-flaring-related CO2 emission. Moreover, these positive impacts are so strong that the significant negative effects of investment in gas utilization projects, natural gas price and participation in Kyoto Protocol, also established by the study, are not strong enough to bring about significant net decreases in the kilograms of CO2 emission due to gas flaring over the period covered. We also find that change in the level of CO2 emission due to gas flaring is not an important factor considered by NNPC in deciding how much gas-flaring-related information to disclose.