This is a myth. The atmospheric co2 levels have not shown a rising trend. There is a natural pattern of rising and falling but some current studies are actually showing the co2 levels to be falling. co2 is a natural part of our atmosphere, but some people use this and other things to attempt to promote an agenda for political reasons. Some will say that rising levels of co2 is due to fossil fuel use (caused by man), and this rising co2 is the cause of global warming. The problem is that global warming has not been show to exist. Temperatures around the earth are not rising. The past 10 years or so have actually shown a cooling trend.
Simple answer: the question is flawed because you are assuming that carbon dioxide levels actually are rising. No peer reviewed scientific evidence shows this to be the case. Al Gore's error filled political movie does not count as evidence.
If this is a question for a school assignment this is probably not what the teacher is looking for, even though this is correct.