Hansen et al. (2008)
Also: Hansen et al. 2008
Target Atmospheric CO: Where Should Humanity Aim?
Hansen, J., Sato, M., Kharecha, P., Beerling, D., Berner, R., Masson-Delmotte, V., Pagani, M., Raymo, M., Royer, D.L. & Zachos, J.C. (2008). Target Atmospheric CO: Where Should Humanity Aim?. The Open Atmospheric Science Journal. 2(1),217-231. PDF
https://doi.org/10.2174/1874282300802010217
References
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.