The Merry Month of May When We'll Hit a CO2 Danger Point

Lovely soft morning with the trees leafing out and the forsythia in bloom, which are reasons to wait for the beginning of May around here.  But Le Devoir reports on another thing that will happen this coming month that makes the day seem less promising: a UN warning that the world is about to cross a milestone level of 400 ppm CO2 in the atmosphere.

Looking a little further I found this interesting report on the PhysOrg website in which UN climate chief Christiana Figueres opened a conference of the Intergovernmental Panel on Climate Change (IPCC), by pointing out that the organization has said the atmospheric CO2 level must be limited to 400 ppm for Earth's average temperature rise to be contained at between two and 2.4 degrees Celsius (3.6 and 4.3 degrees Fahrenheit).

If not, we're headed for some major changes, documents accompanying Figueres warning said: Atmospheric levels of CO2, the main greenhouse gas, were probably last as high as 400 ppm in the Pliocene period, between 3.2 million and five million years ago when Earth was a warmer place.
The carbon concentration never exceeded 300 ppm for some 800,000 years, it added. Before the Industrial Revolution, when man first started pumping carbon into the atmosphere by burning fossil fuels, CO2 levels were at about 280 ppm.