Because city dwellers have limited exposure to the positive effects of CO2, they view it as dangerous, rather than beneficial. They smoke the pot but don’t understand that their favorite bit of greenery relies heavily on the CO2 they fear so much.
…All of which begs the question: Why aren’t blue urbanites changing their minds along with everyone else? I think it’s because living in the city, they don’t know diddly-squat about the important role CO2 plays in making green things grow. When they think of CO2, they assume it’s this:
What you’re looking at there is smog in Beijing. According to Wikipedia, “visible air pollution is composed of nitrogen oxides, sulfur oxides, ozone, smoke or particulates among others (less visible pollutants include carbon monoxide, CFCs and radioactive sources).” CO2 is not a major smog component.