Context: According to a new study, Researchers have found that rising atmospheric carbon dioxide (CO2) concentrations will cause urban and indoor levels of the gas to increase, which may significantly reduce our basic decision-making ability and complex strategic thinking. 
Key Findings

• By the end of the century, people could be exposed to indoor CO2 levels up to 1400 parts per million--more than three times today's outdoor levels, and well beyond what humans have ever experienced. 
• Building ventilation typically modulates CO2 levels in buildings, but there are situations when there are too many people and not enough fresh air to dilute the CO2. 
• They also build up in poorly ventilated spaces over longer periods of time, such as overnight while sleeping in bedrooms. 
• Put simply, when we breathe air with high CO2 levels, the CO2 levels in our blood rise, reducing the amount of oxygen that reaches our brains. 
• Studies show that this can increase sleepiness and anxiety, and impair cognitive function. And outdoor CO2 in urban areas is higher than in pristine locations. 
• The CO2 concentrations in buildings are a result of both the gas that is otherwise in equilibrium with the outdoors, but also the CO2 generated by building occupants as they exhale. 
• For findings researchers developed a comprehensive approach that considers predicted future outdoor CO2 concentrations and the impact of localized urban emissions, a model of the relationship between indoor and outdoor CO2 levels and the impact on human cognition. 
• They found that if the outdoor CO2 concentrations do rise to 930 ppm, that would nudge the indoor concentrations to a harmful level of 1400 ppm. At this level, some studies have demonstrated compelling evidence for significant cognitive impairment.
• The cognitive impacts of rising CO2 levels represent what scientists call a "direct" effect of the gas' concentration, much like ocean acidification. 
• In both cases, elevated CO2 itself--not the subsequent warming it also causes--is what triggers harm.