Clement et al. (2009)
Also: Clement et al. 2009
Observational and model evidence for positive low-level cloud feedback.
Clement, A. C., Burgman, R., & Norris, J. R. (2009). Observational and model evidence for positive low-level cloud feedback. Science, 325(5939), 460-464. Link to PDF
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.