If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that [[!teximg Error: <a href="./bff0225684287ec7b920989eb9cf2296.log">failed to generate image from code</a>]] will need to be reduced from its current 385 ppm to at most 350 ppm.

James Hansen, “Target Atmospheric CO_2: Where Should Humanity Aim?”