Global Carbon Dioxide Concentrations Surpass the 400ppm Mark

Here's an interview with Ralph Keeling, son of the climate scientist Charles David Keeling, who developed the well known and much publicized Keeling curve, on the approach of the 400ppm Global Carbon Dioxide Concentration mark: http://www.guardian.co.uk/environment/2013/may/14/record-400ppm-co2-carbon-emissions

Here's also an interview with Prof. Michael Mann from Penn State University:
http://www.youtube.com/watch?v=bvC-VI2EdBY

And if you haven't seen enough yet, here's an article which explains the significance of 400ppm, as well as a really honest talk by David Roberts on the reality we may be facing. This level of CO₂ concentrations has not been seen for three million years - http://www.treehugger.com/climate-change/what-does-world-400-ppm-co2-look.html

Keeling Curve - http://www.treehugger.com/climate-change/what-does-world-400-ppm-co2-look.html