>One of the most important questions on climate is: what level we need to limit CO2 to avoid tipping points?
We’re at 390 ppm (parts per million) now, rising about 2 per year. It was once thought 550 was ok, then 450. James Hansen has argued that 350 ppm is the only really safe target. This is politically unthinkable, technically very difficult – but it’s true.
There are complicated explanations as to why 350 ppm of CO2 is the appropriate target, and a simple one. Credit to Jim Hansen for the complicated one. (Well, that’s the press release which points to the original paper).
The simple one is this:
Premise 1: We’re at 390. (obvious)
Premise 2: Arctic is already melting, and releasing methane. (see here)
Premise 3: The Arctic contains frightening levels of frozen methane. (see here)
Premise 4: That methane will accelerate warming. (obvious)
Argument By Induction: 390 already commits us past the tipping point. (this thing will keep going)
In other words – the level of warming already evident at 390 looks to contain enough momentum to wreck the party. Hence, 350 looks pretty reasonable.
Frightening stuff; one can easily see how this is an existential question (ie, one of survival, not lifestyle) – see the methane post below.
So – invest in technologies that can suck carbon from the air. Faster than trees.