A jaunty road sign on the path to apocalypse was passed today, as the level of carbon dioxide in our planet's air reached a level last seen long before mankind existed. Take a deep breath. Enjoy that air. Soon, you'll be breathing water.

Carbon dioxide has officially passed 400 parts per million, huzzah, huzzah. The NYT tells us what we have to look forward to:

Indirect measurements suggest that the last time the carbon dioxide level was this high was at least three million years ago, during an epoch called the Pliocene. Geological research shows that the climate then was far warmer than today, the world’s ice caps were smaller, and the sea level might have been as much as 60 or 80 feet higher.

Modern humanity's raffish, devil-may-care attitude will be remembered fondly by our great-grandchildren, the fish.

[NYT. Photo: AP]