Bob Henson conveys key features of carbon dioxide at the recent crossing of a measurement series past the 400 parts-per-million point.

Hat tip to the ever interesting Wild Weather Dan, Dr Dan Satterfield, for the link.

Incidentally, the “667 per cm” on the image at the top of this blog is the wavenumber of a major absorption line for carbon dioxide, one which coincides with the peak of the Earth’s blackbody emission spectrum at standard temperatures.