The 304 micron milestone

[Rich Feldman]

We live in the unprecedented period when "composition of dry air" is a topic in popular news.

Atmospheric CO2 concentration hits its annual minimum about now, as the northern hemisphere growing season winds down.
There's been plenty of chatter after news that the _low_ point was above 304 microns partial pressure
(aka 400 ppm) for the first time in history, and probably for the first time in millions of years. (Not counting any short-lived blip that might exist in the paleochemical record, from some super-volcanic event before there were hominids.)

Poking around the Internet, I found a very common "textbook" value is 314 ppm. http://www.aldacs.com/images/StdDryAir.jpg

Here's a 1955 journal article (older than me!) titled "HAS THE AMOUNT OF CARBON DIOXIDE IN THE ATMOSPHERE CHANGED
SIGNIFICANTLY SINCE THE BEGINNING OF THE TWENTIETH CENTURY?" http://docs.lib.noaa.gov/rescue/mwr/083 ... 0-0225.pdf

and a pretty animation from 21st century satellite observations: http://climate.nasa.gov/climate_resources/142/

It's disappointing that the editors chose to run the Autumn timelapse (with major plumes of red) at a much greater speedup than the Late Summer timelapse. Such misleading dramatization does not help to get the point across, except to dummies.