CO2 levels at Mauna Loa passed 400 ppm for the first time yesterday, 13th
May. See:

http://www.esrl.noaa.gov/gmd/ccgg/trends/weekly.html

It is probably the highest value that has occurred there since the start of
the Ice Age. In other words, it is now certain that the Greenland and west
Antarctic ice sheets will disappear, raising sea levels by over 10m. It is
not a matter of whether but when. Moreover, the Arctic sea ice will
disappear first, but the consequences of that are unknown, except that the
melting of the Greenland ice sheet will surely accelerate :-(

Cheers, Alastair.