European Federation of Chemical Engineering
http://dx.doi.org/10.1016/j.psep.2012.10.012 Issue edited by Tim Kruger and Richard DartonView Journal Article / Working Paper
We do not know with certainty what level of greenhouse gases in the atmosphere is compatible with a stable climate and healthy oceans. The IPCC's 2007 report stated that stabilising levels at a concentration equivalent to 450 ppm CO2 would provide a roughly 50/50 chance of staying below a global average temperature rise of 2 °C above pre-industrial. From the perspective of the oceans the ‘safe’ limit may be much lower than 450 ppm – many scientists studying ocean acidification have said that the level of CO2 in the atmosphere needs to be stabilised at no more than 350 ppm.