If humanity wishes to preserve a planet similar to that on which civilisation developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that COโ will need to be reduced from its current 385 ppm [parts per million] to at most 350 ppm... If the present overshoot of this target COโ is not brief, there is a possibility of seeding irreversible catastrophic effects.
James Hansen...99 percent confident that the world really was getting warmer and that there was a high degree of probability that it was due to human-made greenhouse gases.
James HansenWe have at most ten yearsโnot ten years to decide upon action, but ten years to alter fundamentally the trajectory of global greenhouse emissions.
James Hansen