Answer: A decrease in population due to health threats is a possible consequence of decreasing air quality resulting from global warming.
Step-by-step explanation:
When average temperature of Earth keeps on increasing for a longer period of time due to greenhouse gases, increased level of carbon dioxide and other gases etc then it is called global warming.
As humans use oxygen to sustain which is present in the air. So, when there will occur decrease in air quality that results from global warming then it means more illness or diseases will be there.
Hence, people will tend to die more often because of decrease in the air quality their health is getting affected.
Thus, we can conclude that a decrease in population due to health threats is a possible consequence of decreasing air quality resulting from global warming.