Seden - have you got me on ignore or are you unable to read my signature? I have a widget which shows the level of CO2 in the atmopshere in parts per million and it is updated regularly. Current data is for Feb 2011. The value is 391.76 ppm. You quoted "250 to 330 parts per million" - this is woefully imprecise and out of date.
From the site (http://co2now.org):
"Current Data for Atmospheric CO2
The world's most current data for atmospheric CO2 is from measurements at the Mauna Loa Observatory in Hawaii. These high-precision measurements were started by Dave Keeling (shown in the photo) in March 1958.
Today, the monthly average concentration of CO2 in the atmosphere is published by the National Oceanic and Atmospheric Administration (NOAA) within a week after each month ends. The source data is organized into a table and republished here at CO2Now.org so more people can see the latest CO2 level and the important CO2 trend. The table includes the full Mauna Loa instrument record for atmospheric CO2."
We all know CO2 is plant food. I am tired of that hackneyed old line. Water is also plant food but many plants won't survive prolonged flooding. Refer to the other element of my signature for if and when the 'plant food' argument crops up.
