Environmental data and research illustrate that global warming, normally assessed through carbon dioxide (CO₂) and greenhouse gas (GHG) emissions, is a critical element in environmental sustainability and that a shift to decarbonized energy sources is necessary to preserve the environment for future generations. The challenge is that overall global sustainability is more complex than solely focusing on global warming or the environment.

As a potential alternative, NO_x emissions are explored as a potential surrogate for CO₂ and GHG emissions and as an indicator for decarbonization. An added benefit of using NO_x is that it has strong correlations with each pillar of sustainability, and therefore can offer a more encompassing view. Global and country specific NO_x emissions, between 1990 and 2015, are analyzed in a format paralleling the three pillars. Trends show that, while NO_x emissions are increasing, there are improvements in both societal and economic emission intensities. It is also demonstrated that there is no net movement towards decarbonization, and that a paradigm shift will be necessary to achieve the emissions reductions required. As well, human development index appears to be tied to the change in per capita emissions of NO_x over the study period. Overall, NO_x is demonstrated to be a robust and potentially more effective surrogate for CO₂ and GHG emissions in estimating fossil fuel emissions and gauging movement towards decarbonization. The added interconnectedness of NO_x with all three pillars makes it an excellent indicator for tracking progress towards overall sustainability.