I remember as a child reading about the dark ages, and being glad I was born in an age of reason. Sad to see mankind reverting to mindless superstition.

They know a couple of things. One, that 350 is the most important number in the world — as NASA scientists put it two years ago, if carbon in the atmosphere exceeds 350 parts per million we can’t have a planet “similar to the one on which civilization developed and to which life on earth is adapted.” And the bad news is we’re already too high — the air holds 390 parts per million CO2. That’s why the Arctic is melting and the sea rising.
– Bill McKibben

350 ppm is a number which Hansen pulled out of his nether regions. There is no scientific basis for it.