a high level of carbon dioxide in the air _______?

D IS D RGHT ANSWER BABY....

Well, as many people know, carbon dioxide and other green house gases seem to be causing the global warming effect. However, many people haven't heard of GLOBAL DIMMING, which is that the sun is dimming. This is caused by the fumes of airplane trails. Scientists know for a fact that this exists, one reason being that on the day of 9/11, when no planes were allowed to fly in the U.S., the change in temperature in that short time was more drastic than in all of human history. Because of global dimming, which is causing the earth to get cooler, it has actually slowed down the effects of global warming. So, in some ways, carbon dioxide is a harmful gas, because it is causing global warming, but it is also good because global warming and global dimming are canceling each other out, but eather one could become a VERY serious problem in the future

D is the answer according to some authorities.

Releasing more carbon dioxide into the atmosphere would logically call for planting more trees to store it. This is contrary to what we have been doing in recent decades across the world as we increasingly cut and clear forests..

D is the answer

http://en.wikipedia.org/wiki/Greenhouse_effect

http://en.wikipedia.org/wiki/Carbon_dioxide#In_the...

these sites may help

D