Budyko (1969)
Also: Budyko 1969
The effect of solar radiation variations on the climate of the Earth
Budyko, M. (1969). The effect of solar radiation variations on the climate of the Earth. Tellus, 21(5), 39-692891. 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.