The concentration of carbon dioxide (CO
2)in Earth’s atmosphere determines its
contribution to the greenhouse effect and the
rates of plant and algal photosynthesis. The
concentration has increased markedly in the
21st century, at a rate of 2.0 ppm/yr during
2000–2009 and faster since then.[1][2]
[youtube]http://www.youtube.com/watch?v=bvC-VI2EdBY[/youtube]