Question: hi - i spoke to you the other day (Thurs). you said to ask you so u could explain in more detail. Why is the carbon dioxide above in the atmosphere rather than below- why do we need it. Thanks by the way ive voted for you.

Jack Snape answered on 19 Mar 2012:

Hi! Thanks for the vote 🙂
The atmosphere is made up of different gases.. about 78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon dioxide. This mix of gases is fairly constant with height but the air gets thinner the higher up you go (fewer molecules per bit of volume). The big differences in carbon dioxide are between the North and South. There is a lot more carbon dioxide in the Northern half of the earth because most of the carbon dioxide emissions are happening in rich countries in the North.

We need some carbon dioxide in the atmosphere because plants use it (along with sunlight and water) to produce energy to grow. Plants turn carbon dioxide into oxygen, which we need to survive. If we keep putting too much carbon dioxide into the atmosphere, plants can’t turn it into oxygen quickly enough and it starts to build up.

Hope that helps 🙂