This paper aimed to provide a performance index of efficiency assessment for 275 metropolitan areas around the world with environmental indicators provided by the Organizations for Economic Co-operation and Development (OECD) for the year 2010, as the basis to benchmark those best positioned for climate change adaptation. The non-parametric DEA method was applied to analyze the efficiency of the metropolitan areas. Once obtained the DEA efficiency score, the most outstanding performance metropolitan areas were identified accordingly to the established parameters, being a total of 47. After an OLS regression, the environmental indicators proved to be variables correlated but not determinant in relation with carbon emissions both individually and in conjuncture. Despite of this, it does confirm that measurement and monitoring the efficiency performance of these variables can help policy makers assess carbon emissions. The present paper is limited, considering the bad performance is possible entirely related to the high GDP level, therefore the methodology of the model specification of GDP as an input variable which lack further inputs to explain the contamination. This information is not included in the database; intermediate variables are needed to explain the process of GDP level and CO2 emissions.