Bell et al (2000)
Also: Bell et al 2000
Climate assessment for 1998
Bell, G. D., Halpert, M. S., Ropelewski, C. F., Kousky, V. E., Douglas, A. V., Schnell, R. C., & Gelman, M. E. (1999). Climate assessment for 1998. Bulletin of the American Meteorological Society, 80(5s), S1-S48. Link to paper
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.