AS WITH ALL THE great momentous events in life, it came and went without much fanfare. Like the beginning and end of life, it was a small series of obvious next steps that culminated in an occasion so significant that it can’t possibly be fully comprehended by one person.

The event, in this case, was the composition of the atmosphere reaching 400 parts of carbon dioxide for every million other parts.

No alarm sounded when the milestone passed. No parade in the street heralded the moment. No riot erupted.

But this obscure scientific measurement marks the the first time our atmosphere has held so much carbon dioxide in three million years….

Read more: http://www.abc.net.au/environment/articles/2013/05/15/3759118.htm