The Keeling Curve, a graph which shows how much carbon dioxide is in the atmosphere, indicates that the amount will exceed 400 parts per million (ppm) of CO2 very soon. The number, by itself, is not significantly different from 399ppm, which is where we are now, or 401ppm, where we will be soon enough. However, in context, it is a very important number. And it is important not just for climatologists, but also for those concerned with national and global security. (more…)