Previous research found that the linear term of fiscal decentralization promotes carbon emissions, while the non-linear term mitigates it.[clarification needed] It verified the inverted U-shaped curve between fiscal decentralization and carbon emissions.[example needed] Besides, increasing energy prices for non-renewable energy decrease carbon emission due to a substitution effect. Among other explanatory variables, improvement in the quality of institutions decreases carbon emissions, while the gross domestic product increases it. Strengthening fiscal decentralization, lowering non-renewable energy prices,[clarification needed] and improving institutional quality to check the deteriorating environmental quality in the study sample and other worldwide regions can reduce carbon emissions.[129]