We did it, and it's nothing to cheer about.
The world hit the "sobering milestone" of 400 parts per million (ppm) of CO2 on Thursday -- a first in human history -- marking "a moment of symbolic significance on road of idiocy" the world has chosen, as well as a call for urgent climate action.
Reaching this threshold level represents a global failure to address the runaway greenhouse gas emissions; as Al Gore wrote today, it shows "we are reaping the consequences of our recklessness."



