Meehl et al. (2009)
Also: Meehl et al. 2009
Relative increase of record high maximum temperatures compared to record low minimum temperatures in the US
Meehl, G. A., Tebaldi, C., Walton, G., Easterling, D., & McDaniel, L. (2009). Relative increase of record high maximum temperatures compared to record low minimum temperatures in the US. Geophysical Research Letters, 36(23). Link to paper
DOI: 10.1029/2009GL040736
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.