Atmospheric CO2 reaches 400ppm

The levels of CO2 in our atmosphere has reached 400 parts per million, a slightly arbitrary red flag point.  Scientists have been warning that anything about 350ppm will lead to dangerous global warming, so this is pretty bleak news though not surprising.  When this planet last experienced conditions like this, temperatures were 3-4 degrees Celsius higher, and sea levels were between 16 and 131 feet higher than today.  Perhaps the worst news, though, is that the rate of increase in atmospheric CO2 has been increasing slightly, so we’re not even on the right path to fix this problem.  (link)